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The Philosophy and Neuroscience Movement
« on: 2007-10-05 13:13:55 » |
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[Blunderov] A bit dense but a fascinating account of the current state of affairs. It's not everyday that philosophy experiences a revolution so I have read the entire piece into the record. (Sometimes links disappear...)
<Brainwave graphic>
http://www.mindhacks.com/blog/2007/10/a_rough_guide_to_phi.html
October 04, 2007
A rough guide to philosophy and neuroscience:
Philosophy is now an essential part of cognitive science but this wasn't always the case. A fantastic new article, available online as a pdf, describes how during the last 25 years philosophy has undergone a revolution in which it has contributed to, and been inspired by, neuroscience.
The article is by two philosophers, Profs Andrew Brook and Pete Mandik, and it's a wonderful summary of how the revolution occurred and just how we've benefited from philosophers turning their attention to cognitive science.
But it also notes how evidence from psychology and neuroscience is being used by philosophers to better understand concepts - such as perception, belief and consciousness - that have been the concern of thinkers from as far back as the Ancient Greeks.
It's an academic article, so it's fairly in-depth in places, but if you want a concise introduction to some of the key issues philosophy of mind is dealing with, and how this directly applies to current problems in the cognitive sciences, look no further.
The scope is wonderfully broad and there's a huge amount of world-shaking information packed into it.
It's particularly good if you're a psychologist or neuroscientist and want a guide to how philosophy is helping us make sense of the mind and brain.
The article will shortly appear in the philosophy journal Analyse and Kritik but the proofs are available online right now.
pdf *of article 'The Philosophy and Neuroscience Movement' (via BH).
—Vaughan.
*Analyse & Kritik 26/2004 (c Lucius & Lucius, Stuttgart) p. 382–397
Andrew Brook/Pete Mandik
The Philosophy and Neuroscience Movement
Abstract: A movement dedicated to applying neuroscience to traditional philosophical
problems and using philosophical methods to illuminate issues in neuroscience
began about twenty-five years ago. Results in neuroscience have affected how we see
traditional areas of philosophical concern such as perception, belief-formation, and consciousness.
There is an interesting interaction between some of the distinctive features
of neuroscience and important general issues in the philosophy of science. And recent
neuroscience has thrown up a few conceptual issues that philosophers are perhaps best
trained to deal with. After sketching the history of the movement, we explore the
relationships between neuroscience and philosophy and introduce some of the specific
issues that have arisen.
0. Introduction
The exponentially-growing body of work on the human brain of the past few
decades has not only taught us a lot about how the brain does cognition, it
has also had a profound influence on other disciplines that study cognition and
behaviour. A notable example, interestingly enough, is philosophy. A small
movement dedicated to applying neuroscience to traditional philosophical problems
and using philosophical methods to illuminate issues in neuroscience began
about twenty-five years ago and has been gaining momentum ever since. The
central thought behind it is that certain basic questions about human cognition,
questions that have been studied in many cases for millennia, will be answered
only by a philosophically sophisticated grasp of what contemporary neuroscience
is teaching us about how the human brain processes information.
The evidence for this proposition is now overwhelming. The philosophical
problem of perception has been transformed by new knowledge about the vision
systems in the brain. Our understanding of memory has been deepened by
knowing that two quite different systems in the brain are involved in short- and
long-term memory. Knowing something about how language is implemented in
the brain has transformed our understanding of the structure of language, especially
the structure of many breakdowns in language. And so on. On the other
hand, a great deal is still unclear about the implications of this new knowledge
of the brain. Are cognitive functions localized in the brain in the way assumed by
most recent work on brain imaging? Does it even make sense to think of
cognitive activity being localized in such a way? Does knowing about the areas
active in the brain when we are conscious of something hold any promise for
helping with long-standing puzzles about the nature and role of consciousness?
And so on.
As a result of this interest, a group of philosophers and neuroscientists dedicated
to informing each other’s work has grown up. Many of these people now
have Ph.D.-level training or the equivalent in both neuroscience and philosophy.
Much of the work that has appeared has been clustered around five themes,
_ data and theory in neuroscience
_ neural representation and computation
_ visuomotor transformation
_ colour vision
_ consciousness
and two big issues lie in the substructure of all of them,
_ the relationship of neuroscience to the philosophy of science,
and,
_ whether cognitive science will be reduced to neuroscience or eliminated by
it.
We will take up these themes shortly. But first, a sketch of some relevant history.
1. History of Research Connecting Philosophy and Neuroscience
Prior to the 1980’s, very little philosophical work drew seriously on scientific
work concerning the nervous system or vice-versa. Descartes speculated in (1649)
that the pineal gland constituted the interface between the un-extended mind
and the extended body and did some anatomy in laboratories (including on live,
not anaesthetized animals; in his view, animals do not have the capacity to feel
pain) but he is at most a modest exception.
Coming to the 20th century, even when the idea that the mind is simply the
brain was promoted in the mid twentieth century by the identity theorists, aka
central state materialists, they drew upon very little actual brain science. Instead,
the philosophy was speculative, even somewhat fanciful. Some examples.
Herbert Feigl (1958/1967) proposed an autocerebroscope whereby people could
directly observe their own mental/neural processes. This was science fiction, not
science fact or even realistic scientific speculation. Much discussion of identity
theory involved the question of the identification of pain with C-fibre firings (U.
384 Andrew Brook/Pete Mandik
T. Place 1956 and J. C. Smart 1959). But it has been known for a very long time
that the neural basis of pain is much more complicated than that (see Hardcastle
1997 for a recent review).
There were a few exceptions to the general ignorance about neuroscience
among philosophers prior to the 1980s. Thomas Nagel (1971) is an example. In
this paper, he discusses the implications of experiments with commissurotomy
(brain bisection) patients for the unity of consciousness and the person. Dennett
(1978) discusses the question of whether a computer could be built that felt pain
and did a thorough and still interesting summary of what was known about pain
neurophysiology at the time. Barbara Von Eckardt-Klein (1975) discussed the
identity theory of sensations in terms of then-current work on neural coding
by Mountcastle, Libet, and Jasper. But these exceptions were very much the
exception.
The failure of philosophers of the era to draw on actual neuroscientific work
concerning psychoneural identities could not be blamed on any lack of relevant
work in neuroscience. David Hubel and Torsten Wiesel’s (1962) Nobel-prizewinning
work on the receptive fields of visual neurons held great promise for
the identification of various visual properties with various neural processes. A
decade earlier, Donald Hebb (1949) had tried to explain cognitive phenomena
such as perception, learning, memory, and emotional disorders in terms of neural
mechanisms.
In the 1960s, the term ‘neuroscience’ emerged as a label for the interdisciplinary
study of nervous systems. The Society for Neuroscience was founded
in 1970. (It now has more than 25,000 members.) In the mid-1970s, the term
‘cognitive science’ was adopted as the label for interdisciplinary studies of cognition
and the idea took hold that what we mean by ‘mind’ is primarily a set of
functions for processing information. The idea of information processing might
not have been much more than a uniting metaphor without the advent of largecapacity
computers. For over three decades now, real effort has been put into
implementing the relevant functions in computational systems (this is one leading
kind of artificial intelligence). Cognitive Science became institutionalized
with the creation of the Cognitive Science Society and the journal Cognitive
Science in the late 1970s. However, it has not grown the way neuroscience has.
After thirty years, the Cognitive Science Society has about 2000 members.
Until the 1980s, there was very little interaction between neuroscience and
cognitive science. On the philosophical front, this lack of interaction was principled
(if wrong-headed). It was based on a claim, owing to functionalists such
as Jerry Fodor (1974) and Hilary Putnam (1967), that, since cognition could
be multiply realized in many different neural as well as non-neural substrates,
nothing essential to cognition could be learned by studying neural (or any other)
implementation. It is the cognitive functions that matter, not how they are implemented
in this, that, or the other bit of silicon or goopy wetware.
The 1980s witnessed a rebellion against this piece of dogma. Partly this was
because of the development of new and much more powerful tools for studying
brain activity, fMRI (functional magnetic resonance imaging; the ‘f’ is usually
lower-case for some reason) brain scans in particular. In the sciences,
psychologist George Miller and neurobiologist Michael Gazzaniga coined the term
‘cognitive neuroscience’ for the study of brain implementation of cognitive functioning.
Cognitive neuroscience studies cognition in the brain through techniques such
as PET (positron emission tomography) and fMRI that allow us to see how behaviour
and cognition, as studied by cognitive scientists, is expressed in functions
in the brain, as studied by neuroscientists. The idea of relating cognitive processes
to neurophysiological processes was not invented in the 1980s, however.
For example, in the 1970s, Eric Kandel (1976) proposed explaining simple forms
of associative learning in terms of presynaptic mechanisms governing transmitter
release. Bliss and Lomo (1973) related memory to the cellular mechanisms of
long term potentiation (LTP).
In philosophy, an assault on the functionalist separation of brain and mind
was launched with the publication of Patricia (P. S.) Churchland’s Neurophilosophy
in 1986 (a book still in print and widely read). Churchland’s book has
three main aims:
1. to develop an account of intertheoretic reduction and specifically of the
reduction of mind to brain radically different from the one in logical positivist
philosophy of science;
2. to show that consciousness-based objections to psychoneural reduction do
not work,
and,
3. to show that functionalist/multiple realizability objections to psychoneural
reduction do not work.
A later neurophilosophical rebellion against multiple realizability was Bechtel
and Mundale (1997). Their argument was based on the way in which neuroscientists
use psychological criteria in determining what counts as a brain area.
With this sketch of the history of how the philosophy and neuroscience movement
emerged, let us now look at some particular topic areas. We will say
something about the relevant history of each area and examine briefly what is
going on currently. By and large, the topics of primary interest in the philosophy
of neuroscience are topics that tie the issue of the relationship of the mind
(cognition) to the brain into current philosophy of science.
Indeed, it is not always easy to distinguish philosophy of mind from philosophy
of science in the philosophy and neuroscience movement. For example,
the philosophy of mind question, ‘are cognitive processes brain processes?’, is
closely related to the philosophy of science question ‘are psychological theories
reducible to neurophysiological theories?’ Either way, neurophilosophical interest
is mostly concerned with research on the brain that is relevant to the mind
(Gold/Stoljar 1999, explore the relationship of neuroscience and the cognitive
sciences in detail). There are a few exceptions. An important philosophical
study of areas of neuroscience not directly relevant to cognition is Machamer et
al. (2000), who discuss individual neurons, how neurons work, and so on. But
that is the general pattern.
We now turn to the big background issues identified earlier, namely, neuroscience
and the philosophy of science; and reductionism vs eliminativism in
neuroscience and cognitive science.
2. Neuroscience and the Philosophy of Science
In much early philosophy of science, the notion of law is central, as in the
Deductive-Nomological theory of scientific explanation or the Hypothetico-
Deductive theory of scientific theory development or discussions of intertheoretic
reduction. While the nomological view of science seems entirely applicable to
sciences such as physics, there is a real question as to whether it is appropriate
for life sciences such as biology and neuroscience. One challenge is based on
the seeming teleological character of biological systems. Mundale and Bechtel
(1996) argue that a teleological approach can integrate neuroscience, psychology
and biology.
Another challenge to the hegemony of nomological explanation comes from
philosophers of neuroscience who argue that explanations in terms of laws at
the very least need to be supplemented by explanations in terms of mechanisms
(Bechtel/Richardson 1993; Bechtel 2007; Machamer/Craver 2000; Craver 2007).
Here is how their story goes. Nomological explanations, as conceived by the
Deductive-Nomological model, involve showing that a description of the target
phenomenon is logically deducible from a statement of general law. Advocates
of the mechanistic model of explanation claim that adequate explanations of
certain target phenomena can be given by describing how the phenomena results
from various processes and sub-processes. For example, cellular respiration is
explained by appeal to various chemical reactions and the areas in the cell where
these reactions take place. Laws are not completely abandoned but they are
supplemented (Mandik/Bechtel 2002).
One main reason why neuroscience raises issues such as these in stark form
is that, while there is clearly an enormous amount of structure in the brain
(the human brain is made up of roughly 100,000,000,000 neurons), neuroscience
has had very little success in finding general laws that all or nearly all brains
instantiate. Maybe for at least the complex kinds of activity that underpin
cognition, it will turn out that there are no such laws, just masses and masses
of individually-distinct (though still highly structured) events.
A related challenge to logical positivist philosophy of science questions whether
scientific theories are best considered to be sets of sentences at all. Paul (P. M.)
Churchland (1989, 2007), for example, suggests that the vector space model of
neural representation should replace the view of representations as sentences
(more on vector spaces below). This would completely recast our view of the
enterprise of scientific theorizing, hypothesis testing, and explanation. This challenge
is directly connected to the next issue.
3. Reduction Versus Elimination
There are three general views concerning the relation between the psychological
states posited by cognitive science and the neurophysiological processes studied
in the neurosciences:
(1) The autonomy thesis: While every psychological state may be (be implemented
by, be supervenient on) a brain state, types of psychological states will
never be mapped onto types of brain states. Thus, each domain needs to be
investigated by distinct means, cognitive science for cognitively-delineated types
of activity, neuroscience for activities described in terms of brain processes and
structures (Fodor 1974).
Analogy: every occurrence of red is a shape of some kind, but the colour-type,
redness, does not map onto any shape-type. Colours can come in all shapes and
shapes can be any colour (see Brook and Stainton (2000, ch. 4) for background
on the issue under discussion here).
(2) Reductionism: Types of psychological states will ultimately be found to be
types neurophysiological states; every cognitively-delineated type can be mapped
onto some type of brain process and/or structure with nothing much left over.
The history of science has been in no small part a history of such reduction, as
they are (somewhat misleadingly) called (misleading because the reduced kinds
still continue to exist): Chemistry has been shown to be a branch of physics,
large parts of biology have been shown to be a branch of chemistry, and so on.
Reductivists about cognition (or psychology generally) believe that cognition
(and psychology generally) will turn out to be a branch of biology.
(3) Eliminativism (aka eliminative materialism):
Psychological theories are so riddled with error and psychological concepts are so
weak when it comes to building a science out of them that psychological states
are best regarded as talking about nothing that actually exists.
To give just one example of the kind of argument mounted in support of eliminativism,
phenomena identified using psychological concepts are difficult if not
impossible to quantify precisely, but all successful sciences quantify the kinds of
thing of interest. Eliminativist arguments are anti-reductivist in one very important
way: They argue that there is no way to reduce psychological theories
to neural theories and even if there were, there would be no point in doing so.
Philosophers of neuroscience generally fall into either the reductionist or the
eliminativist camps. Most are reductionists of some stripe—most, for example,
take the phenomena talked about in the ‘cognitive’ part of cognitive neuroscience
to be both perfectly real and perfectly well described using psychological
concepts—but most are also not very dogmatic about the matter. If some psychological
concepts turn to be so confused or vague as to be useless for science
or to carve things up in ways that do not correspond to what neuroscience discovers
about what structures and functions in the brain are actually like, most
people in the philosophy and neuroscience movement would accept that these
concepts should be eliminated; we shouldn’t even try to reduce them. Few are
total eliminativists—even the most radical people in the philosophy and neuroscience
movement accept that some of the work of cognitive science will turn out to have
enduring value. To give just one example, though it is a leading
example, almost nobody, not even the ‘high priests’ of eliminativism, Paul and
Patricia Churchland, have ever argued that the concept of consciousness should
be eliminated. Maybe it should be shaped up a bit, trimmed back in places, but
nearly everyone holds that the concept refers to something real and important.
Some philosophers of neuroscience explicitly advocate a mixture of the two.
For instance, the Churchlands seem to hold that ‘folk psychology’ (our everyday
ways of thinking and talking about ourselves as psychological beings) will mostly
be eliminated, but many concepts of scientific psychology will be mapped onto,
‘reduced’ to, concepts of neuroscience. For example, while they have held that
‘folk concepts’ such as belief and desire do not name anything real, scientific
psychological concepts such as representation do (so long as we keep our notion
of representation neutral with respect to the various theories of what representations
are). Many kinds of representation will ultimately be found to be identical
to some particular kind of neural state or process (P. S. Churchland 1986).
In the space we have, we cannot go into the merits of reductivist vs. eliminativist
claims, but notice that the truth of eliminativism will rest on at least
two things:
(1) The first concerns what the current candidates for elimination actually turn
out to be like when we understand them better. For example, eliminativists
about folk psychology often assume that folk psychology views representations
as structured something like sentences and computations over representations
to very similar to logical inference (P. M. Churchland 1981; Stich 1983; P. S.
Churchland 1986). Now, there are explicit theories that representation is like
that. Fodor (1975), for example, defends the ideas that all thought is structured
in a language, a language of thought. But it is not clear that any notion of what
representations are like is built into our very folk concept of representation. The
picture of representation and computation held by most neuroscientists is very
different from the notion that representations are structured like sentences, as we
will see when we get to computation and representation, so if the sententialist
idea were built into folk psychology, then folk psychology would probably be in
trouble. But it is not clear that any such idea is built into folk psychology.
(2) The second thing on which the truth of eliminativism will depend is what
exactly reduction is like. This is a matter of some controversy (Hooker 1981; P.
S. Churchland 1986). For example, can reductions be less than smooth, with
some bits reduced, some bits eliminated, and still count as reductions? Or what
if the theory to be reduced must first undergo some rejigging before it can be
reduced? Can we expect theories dealing with units of very different size and
complexity (as in representations in cognitive science, neurons in neuroscience)
to be reduced to one another at all? And how much revision is tolerable before
reduction fails and we have outright elimination and replacement on our hands?
Bickle (1998) argues for a revisionary account of reduction. McCauley (2001)
argues that reductions are usually between theories at roughly the same level
(intratheoretic), not between theories dealing with radically different basic units
(intertheoretic).
These big issues in the philosophy of neuroscience have been hashed and
rehashed in the past twenty-five years. The burgeoning results in neuroscience
have thrown the issues up in high relief and sometimes have given them new
content. Work on them by philosophers has helped neuroscientists develop a
more precise sense of exactly how their work relates to other scientific work,
cognitive science in particular. It is interesting, even a bit remarkable, that,
as we noted, most people in the philosophy and neuroscience movement have
arrived at roughly the same position on them. Thus, even though they form the
background to most current work, we will say no more about them.
On many more specific topics, we are far from having such a settled position.
We turn now to a representative sample of these topics. We identified them
earlier:
_ Data and theory in neuroscience.
The issue of the relationship of data to theory contains a huge group of subissues.
We will restrict ourselves to two issues: Can introspection generate good data
for neuroscience? And, is function in the brain localized to specific regions (often
referred to as modules) or spread across wide areas of the brain.
_ Neural representation and computation.
A huge topic! Here we will focus on the architecture, syntax, and semantics of
neural representation
_ Visuomotor transformation.
Under this heading, we will examine two issues. The first concerns the hypothesis
that we have two visual systems: one for conscious perception and the other for
action. The second concerns the increasingly popular hypothesis that perception
and control of behaviour are interdependent.
_ Colour vision
Here the big issue is over how to think about the relationship between colour
experiences and the distal stimuli that elicit such experiences. One thing that
is puzzling about this relationship is that the ways in which colours are experienced
diverges quite dramatically from the ways in which their environmental
triggers—the ostensible colours themselves—actually are.
_ Consciousness
Two pressing issues among many in connection with consciousness are the issue,
first, whether consciousness is just a part of cognition or something unique and,
in some measure at least, beyond the reach of either cognitive science or neuroscience
forever and, second, if consciousness is cognitive, what kind of cognitive
process/structure is it, and if it is not, with what kind of cognitive and brain
processes and structures is it associated?1
1Papers discussing all these issues in more detail can be found in Brook/Akins 2005. For
other recent anthologies of articles in the growing intersection of philosophy and neuroscience
see Bechtel et. al 2001, Keeley 2006, and Bickle (in press).
4. Data and Theory: Introspection, Localization, Modularity
4.1 Introspection
In a variety of ways, the advent of sophisticated imaging of brain activity has
created a new reliance on introspection—it is difficult if not impossible to relate
what is going on cognitively to various brain activities without self-reports from
subjects about what is going on in them. Introspection has been in bad odour
as a research tool for over 100 years. It has variously been claimed that
1. introspective claims are unreliable because they are not regularly replicated
in others.
2. subjects confabulate (make up stories) about what is going on in themselves
when they need to do so to make sense of behaviour.
3. introspection has access only to a tiny fraction of what is going on in oneself
cognitively.
4. it is impossible for introspection to access brain states.
And so on. However, researchers into the brain (neuroscience) have been
forced back onto introspection because often the only access that they have to
the cognitive and conscious functions that they want to study in the brain is
the access that the subject him or herself has. It is perhaps a bit ironic that
neuroscience, the most scientific of approaches to human nature to date, has
been forced to fall back onto a technique rejected as unscientific over 100 years
ago!
One interesting middle position gaining some currency is that some of the
limitations in introspection can be overcome by training. After training and
practise introspection can come to be much more reliable than it is in its native
state—perhaps even reliable enough to introspectively identify internal events in
terms of the taxonomy of neuroscience, and thus introspect brain states as such
(Churchland 1989; Mandik 2006).
Another way around the classical and classically unreliable appeal to introspection
is to point out that not all first-person utterances are introspective
reports. Perhaps when first-person utterances are expressing feelings, for example,
they are or at least can be more reliable sources of data that first-person
utterances that report self-observations are. Among other things, with first person
utterances that express rather than report, there may no longer be a conflict
between the use of subjectively-rooted utterances and the requirement that evidence
be public.
4.2 Localization
A question with a long history in the study of the brain concerns how localized
cognitive function is. Early localization theorists (early 1800s) included the
phrenologists Gall and Spurzheim. Flourens was a severe early critic of the idea
from the same period.
Localizationism re-emerged in the study of the linguistic deficits of aphasic
patients of Bouillaud, Auburtin, Broca, and Wernicke in the mid 1800s. Broca
noted a relation between speech production deficits and damage to the left cortical
hemisphere especially in the second and third frontal convolutions. Thus
was ‘Broca’s area’ born. It is considered to be a speech production locus in the
brain. Less than two decades after Broca’s work, Wernicke linked linguistic comprehension
deficits with areas in the first and second convolutions in temporal
cortex now called ‘Wernicke’s Area’.
The lesion/deficit method of inferring functional localization raises several
questions of its own, especially for functions such as language for which there are
no animal models (Von Eckardt 1978). Imaging technologies help alleviate some
of the problems encountered by lesion/deficit methodology (for instance, the
patient doesn’t need to die before the data can be collected!). We mentioned two
prominent imaging techniques earlier: positron emission tomography, or PET,
and functional magnetic resonance imaging, or fMRI. Both have limitations,
however. The best spatial resolution they can achieve is around 1mm. A lot of
neurons can reside in a 1mm by 1mm space! And there are real limitations on
how short a time-span they can measure, though these latter limitations vary
from area to area and function to function. However, resolution improves every
year, especially in fMRI.
In PET, radionuclides possessing excessive protons are used to label water or
sugar molecules that are then injected into the patient’s blood stream. Detectors
arranged around the patient’s head detect particles emitted in the process of the
radioactive decay of the injected nuclides. PET thus allows the identification of
areas high in blood flow and glucose utilization, which is believed to be correlated
with level of neural and glial cell activity (a crucial and largely untested, maybe
untestable, assumption). PET has been used to obtain evidence of activity in
anterior cingulate cortex correlated with the executive control of attention, for
example, and to measure activity in neural areas during linguistic tasks like
reading and writing (Caplan/Carr/Gould/Martin 1999). For a philosophical
treatment of issues concerning PET, see Stufflebeam and Bechtel (1997).
fMRI measures amount of oxygenation or phosphorylation in specific regions
of neural tissue. Amounts of cell respiration and cell ATP utilization are taken to
indicate amount of neural activity. fMRI has been used to study the localization
of linguistic functions, memory, executive and planning functions, consciousness,
memory, and many, many other cognitive functions. Bechtel and Richardson
(1993) and Bechtel and Mundale (1997) discuss some of the philosophical issues
to do with localization.
However much MRI may assume and depend on the idea that cognitive function
is localized in the brain, the idea faces grave difficulties. Even a system
as simple and biologically basic as oculomotor control (the control system that
keeps the eyes pointed in one direction as the head moves around, for example)
is the very reverse of localized. Units dispersed widely across cortex contribute
to performing this function. Moreover, many of these units are also involved
in many other information-processing and control activities. A further factor
pointing in the same anti-localization direction is that the brain is very plastic,
especially in childhood. If one area is damaged, often another area can take over
the functions previously performed by the damaged area. (Since these claims
arise from actually observing how the brain does things, they also undermine
the old idea that we can study cognitive function without studying the brain.)
4.3 Modularity
The question of localization connects to the question of modularity, another big
issue in cognitive neuroscience. Fodor (1983) advanced a strong modularity thesis
concerning the cognitive architecture of peripheral systems (vision, language,
touch, and the like). According to Fodor, a module is defined in terms of the
following properties (1) domain specificity, (2) mandatory operation, (3) limited
output to central processing, (4) rapidity, (5) information encapsulation,
(6) shallow outputs, (7) fixed neural architecture, ( characteristic and specific
breakdown patterns, and (9) characteristic pace and sequencing of development.
Fodor then argued that most of the brain’s peripheral systems are modular,
sometimes multi-modular, while the big central system in which the thinking,
remembering, and so on is done, is emphatically not.
Fodor’s account can be resisted in two ways. One is to argue that he has
an overly restricted notion of what a module has to be like. The other is to
argue that, no matter how characterized, there are precious few if any modules
in the brain. The latter is what the work sketched two paragraphs ago would
suggest. Another body of evidence supporting the same conclusion concerns
back projection. Temporal cortical areas implicated in high levels of visual
processing, for example, send back projections to lower level areas in primary
visual cortex which in turn send back projections to even lower areas in the lateral
geniculate nuclei and ultimately back to the retina. Applebaum (1998) argues for
similar phenomena in speech perception: higher-level lexical processing affects
lower-level phonetic processing. In fact, neuroscientific research shows that back
projections are to be found everywhere. But where there are back projections,
there cannot be encapsulated modules.
5. Neural Representation and Computation
Neural representation and computation is a huge topic, as we said. We will start
with neural representation.
The neurophilosophical questions concerning computation and representation
nearly all assume a definition of computation in terms of transformation of representations.
Thus, most questions concerning computation and representation
are really questions about representation. Contributions to this topic can be
thought of as falling into three groups, though the boundaries between them are
far from crisp. There are questions to do with architecture, question to do with
syntax, and questions to do with semantics. The question of architecture is the
question of how a neural system having syntax and semantics might be structured.
The question of syntax is the question of what the formats or permissible
formats of the representations in such a system might be and how representations
interact with each other based on their form alone. The questions of semantics
is the question of how it is that such representations come to represent—how
they come to have content, meaning.
5.1 Architecture of Neural Representation
Here is some of the thinking afoot currently about neural architecture. Past approaches
to understanding the mind, including symbolicism, connectionism, and
dynamicism, rely heavily on metaphors. A much less metaphorical approach,
or so it is claimed, unifies representational and dynamical descriptions of the
mind. First, representation is rigorously defined by encoding and decoding relations.
Then, the variables identified at higher levels are treated as state variables
in control theoretical descriptions of neural dynamics. Given the generality of
control theory and representation so defined, it is claimed that this approach is
sufficiently powerful to unify descriptions of cognitive systems from the neural
to the psychological levels. If so, contrary to dynamicist arguments (van Gelder
1998), one can have both representation and dynamics in cognitive science.
5.2 Neural syntax
The standard way of interpreting synaptic events and neural activity patterns as
representations is to see them as constituting points and trajectories in vector
spaces. The computations that operate on these representations will then be
seen as vector transformations (P. M. Churchland 1989). This is thus the view
adopted in much neural network modelling (connectionism, parallel distributed
processing). The system is construed as having network nodes (neurons) as its
basic elements and representations are states of activations in sets of one or more
neurons. (Bechtel/Abrahamsen 2002; Clark 1993).
Recently, work in neural modelling has started to become even more finegrained.
This new work does not treat the neuron as the basic computational
unit, but instead models activity in and interactions between patches of the neuron’s
membrane (Bower/Beeman 1995). Thus, not only are networks of neurons
viewed as performing vector transformations, but so are individual neurons.
Neural syntax consists of the study of the information-processing relationships
among neural units, whatever one takes the relevant unit to be. Any
worked-out story about the architecture of neural representation will hold implications
for neural syntax, for what kind of relationships neural representations
will have to other neural representations such that they can be combined and
transformed computationally.
5.3 Neural semantics
Cognitive science and cognitive neuroscience are guided by the vision of
information-processing systems. A crucial component of this vision is that states
of the system carry information about or represent aspects of the external world
(see Newell 1980). Thus, a central role is posited for intentionality, a representation
being about something, mirroring Franz Brentano’s (1874) insistence on
its importance a century before (he called it ‘the mark of the mental’, only a
slight exaggeration).
How do neural states come to have contents? There are three broad answers
to this question that have been popular in philosophy: The isomorphism approach,
the functional role approach and the informational approach. All three
appear in the philosophy of neuroscience.
Proponents of the isomorphism approach construe representation as a relation
of resemblance that obtains between representations and that which they
represent. Such resemblances are often thought to be abstract or second-order
resemblance, meaning, for instance even though a representation and what it
represents might not have a first-order resemblance of being, e.g., the same
colour, they may still enter into systems of relationships such that the relationships
may be mapped onto one another (as in the mapping of various heights
of a mercury column in a thermometer onto various temperatures). (See, for
instance, Churchland 2007; Mandik et. al 2007; O’Brien/Opie 2004).
Proponents of functional role semantics propose that the content of a representation,
what it is about, is determined by the functional/causal relations
it enters into with other representations (Block 1986). For informational approaches,
a representation has content, is about something, in virtue of certain
kinds of causal interactions with what it represents (Dretske 1981, 1988). In
philosophy of neuroscience, Paul Churchland has subscribed to a functional role
semantics at least since 1979. His account is further fleshed out in terms of
state-space semantics (P. M. Churchland 1989; 1995). However, certain aspects
of Churchland’s 1979 account of intentionality also mirror informational
approaches.
The neurobiological paradigm for informational semantics is the feature detector,
for example, the device in a frog that allows it to detect flies. Lettvin
et al. (1959) identified cells in the frog retina that responded maximally to
small shapes moving across the visual field. Establishing that something has
the function of detecting something is difficult. Mere covariation is often insufficient.
Hubel and Wiesel (1962) identified receptive fields of neurons in striate
cortex that are sensitive to edges. Did they discover edge detectors? Lehky and
Sejnowski (1988) challenge the idea that they had, showing that neurons with
similar receptive fields emerge in connectionist models of shape-from-shading
networks. (See P. S. Churchland/Sejnowski 1992 for a review.) Akins (1996)
offers a different challenge to informational semantics and the feature detection
view of sensory function through a careful analysis of thermoperception. She
argues that such systems are not representational at all.
One issue of considerable interest is how the brain does time. How the brain
does objective time, actual persistence, is interesting enough but even more
interesting is the subjective time of behaviour: the temporal representation that
is analogous to egocentric space (in contrast to objective or allocentric space).
How can times be represented in the brain so that when we recall them, we recall
them as falling into a temporal order. How, for example, when we recall a series
of sounds that we have heard, do we hear it as a melody rather than as a chord?
As was true of neural syntax, any worked-out story about the architecture of
neural representation will hold implications for neural semantics, for the question
of how neural representations can come to have content, meaning, be about states
of affairs beyond themselves.
5.4 Visuomotor Transformation
A specific but absolutely central topic to do with neural representation is visuomotor
transformation, that is to say, how we use visual information to guide
motor control.
Here the leading theory, due to Milner and Goodale (1995), is that we have
two complementary visual systems, vision-for-perception and vision-for-action.
They base their conclusion on a double dissociation between two kinds of disorder
found in brain-lesioned human patients: visual form agnosia and optic ataxia.
Milner and Goodale claim that this functional distinction mirrors the anatomical
distinction between the ventral pathway (to the side and near the bottom of the
brain) and the dorsal pathway (to the rear and near the top of the brain) in the
visual system of primates. Probably no other claim in cognitive neuroscience
has attracted as much attention as this one in the past ten or twelve years.
Another important body of work in visuomotor control focuses on the idea
that spatial perception and motor output are interdependent. There are two
broad approaches. One posits mental representations mediating between perception
and action. This approach is often called representationalism. The
other approach, a kind of antirepresentationalism, opposes this idea, arguing
that intelligent, visually guided behaviour can be explained without positing intermediaries
with representational or semantic properties between sensory input
and motor output.
5.5 Colour Vision
The final two issues on which we will focus in this quick survey of issues currently
at the interface between philosophy and neuroscience are colour vision
and consciousness. Any complete theory of neural representation would have to
contain a theory of both.
The biggest issue to do with colour vision, as we said, is the issue of how
to think about the relationship of colour experience to the causal factors that
produce colour experience. For example, experiences of different colours are the
result of combinations of intensities of light of the three broad wavelengths of
light to which the retina is sensitive (four wavelengths in some women) plus other
factors. Light of three intensities at three wavelengths is nothing like redness as
one experiences it. So how should we think of the relationship between the two?
Even worse, some argue that colour experience arises from processing that
distorts the stimulus features that are its main causes, thereby largely constructing
a world of perceived colour that has almost nothing to do with how the world
actually is. For these people, perceived colour similarity is a systematic misrepresentation
of the corresponding stimuli. How such systematic misrepresentation
could have come to have a survival or reproductive advantage is just one of the
puzzling, even baffling questions to which contemporary work in neuroscience
on colour gives rise.
Most remarkably of all, we can have colour experiences that represent physically
impossible colours. In a stunning example of neurophilosophy at work, Paul
Churchland (2005) has shown that by exploiting shifts in experienced colour due
to tiredness and habituation, experiences of colour can be brought about where
the colours could not exist on standard colour wheels and other theories of the
structure of colour and, moreover, would require physically-impossible states, for
example, that things in one’s world be emitting light and be emitting no light
at the same time. Indeed, as Churchland shows, some of the colour experiences
that we can have cannot even be represented by a colour sample.
6. Consciousness
Most of the philosophical interest in consciousness starts from the question of
whether consciousness could possibly be a physical process of any kind, let alone
a brain process. A common view in philosophy of neuroscience is that everything
to do with the mind, including consciousness, will turn out to be explicable in
terms of neurophysiology—not even explanatory autonomy is allowed. If consciousness
is not something that neuroscience can capture, then that hallowed
shibboleth of neuroscience will be false and there will be at least severe limitations
on the extent to which there could ever be a science of consciousness.
In the face of claims that at least something about consciousness is not neural
or even physical at all, cognitive neuroscientists and their philosopher fellowtravellers
have tended to one or the other of three different kinds of reaction:
1. They try to show that the claim is wrong (or incoherent, or in some other
way epistemically troubled) (Dennett 1991; 1995; Tye 1993; Brook/Raymont,
forthcoming). Or,
2. They just ignore the claim. This is the approach taken by many cognitive
and neuro-scientists. Or,
3. They throw science at it and attempt implicitly or explicitly to produce the
kind of account that is supposed to be impossible (Dennett 1978; Hardin
1988; Clark 1993; Akins 1993a; 1993b; 1996; Hardcastle 1997; Baars 1988;
Rosenthal 1991; Mandik, in press).
The usual way to argue the main idea in (1), that there is nothing unique or
sui generis about consciousness, is to tackle the arguments that claim that there
is and try to show that they do not work. Here is a sample of such arguments.
Nagel (1974) argued that because conscious experience is subjective, i.e., directly
accessible by only the person who has it, we are barred from ever understanding
it fully, including whether and if so how it could be physical. For example, even if
we knew all there is to know about bat brains, we would not know what it is like
to be a bat because bat conscious experience would be so different from human
conscious experience. Later, Jackson (1986), McGinn (1991), Chalmers (1996),
and others extended this line of thought with zombie thought experiments and
thought experiments about colour scientists who have never experienced colour.
Zombie thought experiments are representative of the genre. Consider what
philosophers call qualia: the introspectible aspects of conscious experiences,
what it is like to be conscious of something. Those who hold that consciousness
is something unique argue that there could be beings who are behaviourally,
cognitively, and even physically exactly like us, yet they have no conscious experience
at all. If so, conscious experience cannot be a matter of behaviour,
cognition, or physical makeup.
A variant, inverted spectrum thought experiments, urge that others could
have radically different conscious experience of, in this case, colour with no
change in behaviour, cognition, or physical makeup. For example, they might see
green where we see red (inverted spectrum) but, because of their training, etc.,
they use colour words, react to coloured objects, and even process information
about colour exactly as we do. If inverted spectra are possible, then the same
conclusion follows as from the alleged possibility of zombies: consciousness is
not safe for neuroscience.
Zombie and inverted spectra arguments strive to show that representations
can have functionality as representations without consciousness. A more scientific
way to argue for a similar conclusion involves appeal to cases of blind
sight and inattentional blindness. Due to damage to the visual cortex, blindsight
patients have a scotoma, a ‘blind spot’, in part of their visual field. Ask
them what they are seeing there and they will say, “Nothing”. However, if you
ask them instead to guess what is there, they guess with far better than chance
accuracy. If you ask them to reach out to touch whatever might be there, they
reach out with their hands turned in the right way and fingers and thumb at
the right distance apart to grasp anything that happens to be there. And so on
(Weiskrantz 1986).
Inattentional blindness and related phenomena come in many different forms.
In one form, a subject fixates (concentrates) on a point and is asked to note some
feature of an object introduced on or within a few degrees of fixation. After a
few trials, a second object is introduced, in the same region but usually not in
exactly the same place. Subjects are not told that a second object will appear.
When the appearance of the two objects is followed by 1.5 seconds of masking,
at least one-quarter of the subjects and sometimes almost all subjects have no
awareness of having seen the second object.2
There is a sense in which the inattentionally blind are not conscious of what
they missed: they did not notice and cannot report on the item(s). However,
it can be argued that in another sense, they are conscious of the things on
which they cannot report. For example, their access to the missed items is
extensive, much more extensive than the access that blindsight patients have
to items represented in their scotoma. When the second object is a word, for
example, subjects clearly encode it and process its meaning. Evidence? When
asked shortly after to do, for example, a stem completion task (i.e., to complete
a word of which they have been given the first syllable or so), they complete the
word in line with the word they claim not to have seen much more frequently
than controls do. Thus, subjects’ access to words that they miss involves the
processing of semantic information. If so, their access to the missed words is
much like our access to items in our world when we are conscious of them.
Thus, an alternative account of the ‘blindness’ in these cases is that subjects
are conscious of what they cannot report but are not conscious of being thus
conscious (so they cannot report it). If so, far from inattentional blindness
suggesting that representations can have full functionality without consciousness,
the phenomenon would pull in the opposite direction. At minimum, it seems to
be at least fully compatible with the idea that consciousness is a form of cognition
(see Mandik 2005).
So what about philosophers and neuroscientists who ignore that challenging
claim that consciousness is unique, sui generis, or throw science at it? Their
numbers are legion and we won’t attempt to examine the various alternative
theories here. They range from attention theories to global work space theories
to pandemonium architecture models to connectionist and dynamic systems
models. Recent neuroscience has made a lot of progress in identifying the regions
and systems in the brain most closely associated with consciousness of various
kinds (Koch 2004 gives an excellent summary). What is important here is that
nearly all this work starts from a common assumption, that consciousness is a
fairly standard cognitive phenomenon that can be captured in the kind of theory
that captures cognitive functioning in general, without any attempt to argue for
the assumption.
Ignoring the challenging claim is risky (not to mention a bit rude). It risks
leaving many—and not just dyed-in-the-wool anticognitivists—feeling that the
real thing, consciousness itself, has been left out, that the researcher has covertly
changed the subject and is talking about something else. This is how many
react to suggestions that consciousness is, for example, synchronized firing of
neurons. “Surely”, they react, “you could have the synchronized firing without
consciousness. If so, consciousness is not synchronized firing of neurons. Maybe
this firing pattern is a neural correlate of consciousness (NCC), but it is not
what consciousness is”.
2For more on this fascinating group of phenomena, see Mack, http://psyche.cs.monash.
edu.au/v7/psyche-7-16-mack.html or Mack/Rock 1998.
Throwing science at the challenge faces exactly the same risk. No matter
what the scientific model, sceptics about a science of consciousness can always
claim that the model is not a model of consciousness, that the researcher has
changed the topic to something that can be understood neuroscientifically, is
merely talking about correlates of consciousness (NCCs) or whatever. Moreover,
it would appear that no amount of neuroscience could make this objection
irrational. No matter what the scientific model of consciousness, the charge can
always be levelled that the model is studying mere correlates, that it is not uncovering
the nature of consciousness. Many now believe that the only approach
with any hope of success so far as a science of consciousness is concerned is to
beard the sceptics in their lair, to tackle the arguments that they advance and
show that they just don’t work or worse, are incoherent. To make consciousness
safe for neuroscience, we would have to show one (or both) of two things.
The first would be that the sceptics have given no good reason to believe that
consciousness is not safe for neuroscience. The second, and perhaps stronger,
would be to show that consciousness is not and could not be unique in the way
required by sceptics. Both of these are pre-eminently philosophical tasks.
In general, at the interface between neuroscience and philosophy at the moment,
there is a great ferment. Results in neuroscience are shedding light on,
even reshaping, traditional philosophical hunches about and approaches to the
mind. And neuroscience is throwing up some new issues of conceptual clarification
and examination of possibilities that philosophers are better equipped to
handle than anyone else. We live in interesting times!
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Stufflebeam, R./W.
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Walter Watts
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Just when I thought I was out-they pull me back in
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Re:The Philosophy and Neuroscience Movement
« Reply #1 on: 2007-10-05 16:54:52 » |
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Quote from: Blunderov on 2007-10-05 13:13:55 [Blunderov] A bit dense but a fascinating account of the current state of affairs. It's not everyday that philosophy experiences a revolution so I have read the entire piece into the record. (Sometimes links disappear...)
<Brainwave graphic>
http://www.mindhacks.com/blog/2007/10/a_rough_guide_to_phi.html
October 04, 2007
A rough guide to philosophy and neuroscience:
Philosophy is now an essential
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Aw jeeeez, Edith. What did you do with the funny papers............?
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Walter Watts
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No one gets to see the Wizard! Not nobody! Not no how!
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Blunderov
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Re:The Philosophy and Neuroscience Movement
« Reply #2 on: 2007-10-05 19:57:57 » |
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Quote from: Walter Watts on 2007-10-05 16:54:52
Aw jeeeez, Edith. What did you do with the funny papers............?
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[Blunderov] I'd forgotten about Archie Bunker! Fair enough. Now for something not at all the same
<Graphic :Miss Beatnik 1959 from BeatMuseum>
http://www.hipwax.com/music/oddpop/beattest.html
Beatnik Questionnaire
Do you live like there is no tomorrow?
Are you a Beatnik?
Do you attend poetry readings?
In subterranean caves?
When did you attend your last poetry reading?
Who was reciting?
Name the poems recited:
Did you dig them?
Do you write your own poetry?
Cool verse?
Gone words?
Do you also recite?
In public?
Before a crazy mob?
What kind of a room do you live in:
__ Pad
__ Cell
__ Bakery
__ Cubicle
__ Joint
__ Weird box
__ Dug-out
__ Round room
__ Flop house
__ Two-by-two
__ Pucker Palace
__ Dive
Where do you live:
__ Vitamin Village
__ Beatsville
__ Be-bop Town
__ Squaresville
__ Beatnik Bore
__ Sunnyville
__ Poetryville
__ Down under
__ Crazyville
__ Way out
Have you ever been in trouble?
Were you caught by the fuzz?
Do you drive a hot rod?
Gas rod?
Foot pedaler?
Buggy?
Do you blast your jets easily?
Do you always lose your temper?
Are you gone?
Real gone?
Gone to where?
May I join you?
Do you dig the arts?
What's your talent?
Do you practice?
Are you out of this world?
Flying on cloud nine?
Are you a cool cad?
The complete end?
All gone?
Do you make with the clothes cover?
Do you always wear those crazy quilts?
Are you cooler than a cool Jackson?
Are you always the coolest?
General Qnestions: (All to be answered. Be at least semi-honest.)
Do you believe we live in a cruel world?
Are you doing your best to change it?
Are you a snagged stag?
Are you free for dating?
Have you had your solo flight?
Are you waiting for me?
Do you consider me a:
__ Daddy-o
__ Cookie
__ Almond
__ Doll
__ Cool ghoul
__ Banana
__ Square
__ Snatcher
__ Beakel
__ Kookie
__ Pill pusher
__ Bone eater
__ Cube
__ Coin hoarder
__ Drag
__ Cat
__ Squirrel
__ Dead head
Are you loaded?
Do you have many skins?
Portrait bills?
Do you pay for your dates?
Are you a cheap creep?
Do you beat the drums?
Are you hep?
Do you use the chords?
Are you the utmost?
The utmost of what?
On a date do you act like a:
__ Stiff
__ Kill joy
__ Body digger
__ Way out
__ Bug
__ Poet
__ Angel
__ Real George
__ Tight head
__ Baby
__ Party pooper
__ Ick
Are you a chick?
Chicken?
Plucked chicken?
Cooked chicken?
Have you ever had a date deep-six you?
Do you know why he ditched you?
Which brand coffin nail do you smoke?
Do you mooch them or buy them?
How many coffin nails do you hammer each day?
Do you inhale?
How do you travel:
__ Hot rod
__ Satellite
__ Monkey wagon
__ Shoe leather express
__ Sardine crusher
__ Wagon train
Do you chug the sweet juice?
Are you a freeloader?
Which drinks do you like the best:
__ Moo juice
__ Rooster juice
__ Purple passions
__ Nerve juice
__ Mickey runs
__ Soft brews
How many drinks does it take to get you juiced?
Are you prehistoric?
Jail-bait?
Under 21?
Are you a cool dresser?
Do you wear the regular rags and vines?
Which clothes do you normally wear:
__ Glad threads
__ White float boats
__ Long johns
__ Bright beads
__ Crazy quilts
__ Pullovers
__ Lily whites
__ Sandals
__ Neck tails
__ Head warmers
__ Straw duds
__ Flaps
__ Finger coats
__ Ivy weeds
__ Warmers
Do you like to live it up?
Do you go in for jazzing?
At the end of a date do you expect to:
__ Lump lips
__ Stare blankly
__ Flip your lid
__ Shake hands
__ Flee to the crib
__ Cut the breeze
__ Whisper poetry
__ Beat it
__ Be like Columbus
Do you have a large galaxy of friends?
Do they all wear goatees?
Do you tune me in?
Can we broadcast?
Are we on the same frequency?
Do you think I'm a goop?
Why do you feel that way?
Do you ever think I'm the ginchiest?
Am I really "r e a l crazy?"
When on a date do you always go to the powderbox to plant the platterpuss?
Do you wear shades or can you see without them?
Do they fog up in a storm?
Do I send you?
When we are together are you stimulated to a high pitch of excitement?
Do you mind if I fall by to see you?
Must I use the talkie first?
Would you like to go to a really wild beat party?
For the two of us?
Do you know how to prune?
Can you prune for over a minute?
Are you looking far a present from me?
Such as a tourniquet on your finger?
Are you:
__ Mad
__ Fighting the weather
__ Dippy
__ Off your rocker
__ Crazy
__ Droopy
__ Tilted
__ Hunky
__ Paint happy
__ Way out
__ Jerky
__ Hooked
Are you going steady?
Who chained you?
Can you break loose?
Can we get together for an evening of poetry?
When?
Copyright 1960 by Gimmix Greeting Card Company, Inc., P.O. Box 567, Port Chester, N.Y. 10574, GIMMIX novelty 35H-107
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Blunderov
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"We think in generalities, we live in details"
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Re:The Philosophy and Neuroscience Movement
« Reply #3 on: 2007-11-01 14:08:19 » |
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[Blunderov]"...a problem that philosophers have made essentially no headway in solving".
The classic taunt. The classic retort is that the speaker has apparently not given up hope for philosophy entirely, at least not as far as his own arguments are concerned.
To be fair, philosophy is not known for presenting solutions. Questions yes. Answers not so much.
The author is a scientist. A very good scientist. One who philosophises just as much as is necessary and no more. Good writer too.
http://www.edge.org/3rd_culture/ramachandran07/ramachandran07_index.html
What is the self? How does the activity of neurons give rise to the sense of being a conscious human being? Even this most ancient of philosophical problems, I believe, will yield to the methods of empirical science. It now seems increasingly likely that the self is not a holistic property of the entire brain; it arises from the activity of specific sets of interlinked brain circuits. But we need to know which circuits are critically involved and what their functions might be. It is the "turning inward" aspect of the self — its recursiveness — that gives it its peculiar paradoxical quality.
THE NEUROLOGY OF SELF-AWARENESS [1.8.07]
By V.S. Ramachandran
The Edge 10th Anniversary Essay
Introduction
V.S. RAMACHANDRAN, a neuroscientist, is Director, Center for Brain and Cognition, University of California, San Diego; Author, A Brief Tour of Human Consciousness, and coauthor, Phantoms in the Brain.
V.S. Ramachandran's Edge Bio Page
--------------------------------------------------------------------------------
THE NEUROLOGY OF SELF-AWARENESS
What is the self? How does the activity of neurons give rise to the sense of being a conscious human being? Even this most ancient of philosophical problems, I believe, will yield to the methods of empirical science. It now seems increasingly likely that the self is not a holistic property of the entire brain; it arises from the activity of specific sets of interlinked brain circuits. But we need to know which circuits are critically involved and what their functions might be. It is the "turning inward" aspect of the self — its recursiveness — that gives it its peculiar paradoxical quality.
It has been suggested by Horace Barlow, Nick Humphrey, David Premack and Marvin Minsky (among others) that consciousness may have evolved primarily in a social context. Minsky speaks of a second parallel mechanism that has evolved in humans to create representations of earlier representations and Humphrey has argued that our ability to introspect may have evolved specifically to construct meaningful models of other peoples minds in order to predict their behavior. "I feel jealous in order to understand what jealousy feels like in someone else" — a short cut to predicting that persons behavior.
Here I develop these arguments further. If I succeed in seeing any further it is by "standing on the shoulders of these giants". Specifically, I suggest that "other awareness" may have evolved first and then counterintutively, as often happens in evolution, the same ability was exploited to model ones own mind — what one calls self awareness. I will also suggest that a specific system of neurons called mirror neurons are involved in this ability. Finally I discuss some clinical examples to illustrate these ideas and make some testable predictions.
There are many aspects of self. It has a sense of unity despite the multitude of sense impressions and beliefs. In addition it has a sense of continuity in time, of being in control of its actions ("free will"), of being anchored in a body, a sense of its worth, dignity and mortality (or immortality). Each of these aspects of self may be mediated by different centers in different parts of the brain and its only for convenience that we lump them together in a single word.
As noted earlier there is one aspect of self that seems stranger than all the others — the fact that it is aware of itself. I would like to suggest that groups of neurons called mirror neurons are critically involved in this ability.
The discovery of mirror neurons was made G. Rizzolati, V Gallase and I Iaccoboni while recording from the brains of monkeys performed certain goal-directed voluntary actions. For instance when the monkey reached for a peanut a certain neuron in its pre motor cortex ( in the frontal lobes) would fire. Another neuron would fire when the monkey pushed a button, a third neuron when he pulled a lever. The existence of such Command neurons that control voluntary movements has been known for decades. Amazingly, a subset of these neurons had an additional peculiar property. The neuron fired not only (say) when the monkey reached for a peanut but also when it watched another monkey reach for a peanut!
These were dubbed "mirror neurons" or "monkey-see-monkey-do" neurons. This was an extraordinary observation because it implies that the neuron (or more accurately, the network which it is part of) was not only generating a highly specific command ("reach for the nut") but was capable of adopting another monkey's point of view. It was doing a sort of internal virtual reality simulation of the other monkeys action in order to figure out what he was "up to". It was, in short, a "mind-reading" neuron.
Neurons in the anterior cingulate will respond to the patient being poked with a needle; they are often referred to as sensory pain neurons. Remarkably, researchers at the University of Toronto have found that some of them will fire equally strongly when the patient watches someone else is poked. I call these "empathy neurons" or "Dalai Lama neurons" for they are, dissolving the barrier between self and others. Notice that in saying this one isn't being metaphorical; the neuron in question simply doesn't know the difference between it and others.
Primates (including humans) are highly social creatures and knowing what someone is "up to" — creating an internal simulation of his/her mind — is crucial for survival, earning us the title "the Machiavellian primate". In an essay for Edge (2001) entitled "Mirror Neurons and the Great Leap Forward" I suggested that in addition to providing a neural substrate for figuring out another persons intentions (as noted by Rizzolati's group) the emergence and subsequent sophistication of mirror neurons in hominids may have played a crucial role in many quintessentially human abilities such as empathy, learning through imitation (rather than trial and error), and the rapid transmission of what we call "culture". (And the "great leap forward" — the rapid Lamarckian transmission of "accidental") one-of-a kind inventions.
I turn now to the main concern of this essay — the nature of self. When you think of your own self, what comes into mind? You have sense of "introspecting" on your own thoughts and feelings and of " watching" yourself going about your business — as if you were looking at yourself from another persons vantage point. How does this happen ?
Evolution often takes advantage of pre-existing structures to evolve completely novel abilities. I suggest that once the ability to engage in cross modal abstraction emerged — e.g. between visual "vertical" on the retina and photoreceptive "vertical" signaled by muscles (for grasping trees) it set the stage for the emergence of mirror neurons in hominids. Mirror neurons are also abundant in the inferior parietal lobule — a structure that underwent an accelerated expansion in the great apes and, later, in humans.. As the brain evolved further the lobule split into two gyri — the supramarginal gyrus that allowed you to "reflect" on your own anticipated actions and the angular gyrus that allowed you to "reflect" on your body (on the right) and perhaps on other more social and linguistic aspects of your self (left hemisphere) I have argued elsewhere that mirror neurons are fundamentally performing a kind of abstraction across activity in visual maps and motor maps. This in turn may have paved the way for more conceptual types of abstraction; such as metaphor ("get a grip on yourself").
How does all this lead to self awareness? I suggest that self awareness is simply using mirror neurons for "looking at myself as if someone else is look at me" (the word "me" encompassing some of my brain processes, as well). The mirror neuron mechanism — the same algorithm — that originally evolved to help you adopt another's point of view was turned inward to look at your own self. This, in essence, is the basis of things like "introspection". It may not be coincidental that we use phrases like "self conscious" when you really mean that you are conscious of others being conscious of you. Or say "I am reflecting" when you mean you are aware of yourself thinking. In other words the ability to turn inward to introspect or reflect may be a sort of metaphorical extension of the mirror neurons ability to read others minds. It is often tacitly assumed that the uniquely human ability to construct a "theory of other minds" or "TOM" (seeing the world from the others point of view; "mind reading", figuring out what someone is up to, etc.) must come after an already pre- existing sense of self. I am arguing that the exact opposite is true; the TOM evolved first in response to social needs and then later, as an unexpected bonus, came the ability to introspect on your own thoughts and intentions. I claim no great originality for these ideas; they are part of the current zeitgeist. Any novelty derives from the manner in which I shall marshall the evidence from physiology and from our own work in neurology. Note that I am not arguing that mirror neurons are sufficient for the emergence of self; only that they must have played a pivotal role. (Otherwise monkeys would have self awareness and they don't). They may have to reach a certain critical level of sophistication that allowed them to build on earlier functions (TOM) and become linked to certain other brain circuits, especially the Wernickes ("language comprehension") area and parts of the frontal lobes.
Does the mirror neuron theory of self make other predictions? Given our discovery that autistic children have deficient mirror neurons and correspondingly deficient TOM, we would predict that they would have a deficient sense of self (TMM) and difficulty with introspection. The same might be true for other neurological disorders; damage to the inferior parietal lobule/TPO junction (which are known to contain mirror neurons) and parts of the frontal lobes should also lead to a deficiency of certain aspects self awareness. (Incidentally, Gallup's mirror test — removing a paint splotch from your face while looking at a mirror — is not an adequate test of self awareness, even though it is touted as such. We have seen patients who vehemently claim that their reflection in the mirror is "someone else" yet they pass the Gallup test!)
It has recently been shown that if a conscious awake human patient has his parietal lobe stimulated during neurosurgery, he will sometimes have an "out of body" experience — as if he was a detached entity watching his own body from up near the ceiling. I suggest that this arises because of a dysfunction in the mirror neuron system in the parieto-occipital junction caused by the stimulating electrode. These neurons are ordinarily activated when we temporarily "adopt" another's view of our body and mind (as outlined earlier in this essay). But we are always aware we are doing this partly because of other signals (both sensory and reafference/command signals) telling you you are not literally moving out of yourself. (There may also be frontal inhibitory mechanisms that stop you from involuntarily mimicking another person looking at you). If these mirror neuron-related mechanisms are deranged by the stimulating electrode the net result would be an out-of-body experience. Some years ago we examined a patient with a syndrome called anosognosia who had a lesion in his right parietal lobe and vehemently denied the paralysis. Remarkably the patient also denied the paralysis of another patient sitting in an adjacent wheelchair! (who failed to move the arm on command from the physician.) Here again was, evidence that two seemingly contradictory aspects of self — its the individuation and intense privacy vs. its social reciprocity — may complement each other and arise from the same neural mechanism, mirror neurons. Like the two sides of a Mobius strip, they are really the same, even they appear — on local inspection — to be fundamentally different.
Have we solved the problem of self? Obviously not — we have barely scratched the surface. But hopefully we have paved the way for future models and empirical studies on the nature of self, a problem that philosophers have made essentially no headway in solving. (And not for want of effort — they have been at it for three thousand years). Hence our grounds for optimism about the future of brain research — especially for solving what is arguably Science's greatest riddle.
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