Body Representation:

The topic in psychology with
which I am most engaged at the moment is that of body representation. This is
essentially the question of how the brain constructs its internal
representation of the body in which it resides, controls, and has the peculiar
phenomenology of ownership for. This is a highly nuanced question that
encroaches on issues previously relegated to the realm of armchair philosophy.
One example is the distinction between self and other implicit in the
generating of the body representation. Another is the aspect of
self-consciousness that emerges from consciousness of one’s body. The nearest
one can get to the scientific study of this issue is through the rubber hand
illusion. This is an intriguing phenomenon that occurs when the brain is fooled
into misattributing a rubber hand to itself through clever setups where the
false hand is placed in a position congruent to the real hand and where both
are touched synchronously, with only the touch on the rubber hand being
visible.

Another
avenue of interesting work in this field is the experimental induction of out
of body experiences, pioneered by Henrik Ehrrson and colleagues at the
Karolinska Institute in Denmark. This occurs using a clever manipulation of
altered reality systems where the cameras were mounted behind seated
participants and their image was displayed on a head-mounted display that
allowed the subjects binocular vision of themselves from behind. They were then
touched on the chest by the experimenter, who was careful to prevent them
vision of this, while simultaneously hovering a ruler under the cameras in
clear vision of the subjects. This is effectively a whole-body generalization
of the rubber hand illusion, and is said to produce a similar phenomenology of body
dissociation and misattribution. 

These
methods provide an experimental method to probe the mechanisms of body
representation and, in particular, the malfunctioning or the erroneous
functioning, of this system. That it is possible for the brain to perceive a
rubber hand as part of itself despite the rebellion of the cognitive system’s
clear knowledge that this cannot be is a truly remarkable fact. It is a triumph
of bottom-up over top-down, where the discursive and reflective parts of the
brain are issuing down the results of their evaluation that arrive
insignificantly to the perceptual apparatus of the brain that continues to
maintain its illusory self-attribution of the patently false arm. In studying
the conditions that give rise to this phenomenon, we can hope to attain an
understanding, at least a rough one, of how the brain comes to generate its
representation of the body it inhabits. So far as we can currently tell, this
illusory perception results from what Ramachandran calls the “Bayesian logic”
of the brain, which is an inferential process that attempts to create an
internal representation of the world and all sensible objects therein, in this
case the body, via a causal inference that operates on the sensory signals that
impinge on the body. If these signals are correlated in just the right ways –
that is, in ways likely to have been generated by the same object – then the
brain creates an object from which these sensory signals originate. And, all
objects which give rise to tactile signals must be part of the body; this in
the Bayesian framework would be called the ‘prior’, an assumption or constraint
that the brain implements.

Consciousness:

Another
phenomenon that I am deeply fascinated by is consciousness. Arthur Schopenhauer
speaks of this phenomenon as ‘the necessary correlate’ of the world, which
whomever possesses powerful enough reflective capacities would be able to
realize as the fundamental carrier and supporter of the whole of perceptual
reality. I share a similar conviction with him and recognize the enormous
importance and generality of this concept. It is one of the most universal concepts
– second only to existence itself, if this latter isn’t also subsumed within it,
which it arguably is. As Plato instructs us in the practice of philosophy to
search for the general in the particular, our abstracting mind cannot find
anything under which to subsume the concept of consciousness, and this is so precisely
because of its fundamental nature as that which conditions the whole world of empirical
reality as observed.

All this
fluffy philosophical talk aside, there has recently been a tremendous amount of
effort and research directed towards the scientific study of this ephemeral
topic. Theories abound and every cognitive researcher worth his buck has a pet
theory, whether it is framed in neural, cognitive, or information theoretic
terms. Alongside this profuse theorizing are ingenious experimental designs
that allow us to actually study mechanisms that give rise to phenomenal consciousness.
Some search for the neural correlate of consciousness (NCC) while others look
for neural signatures of changes in its content, and others take different
approaches.

My current favorite theory of
consciousness is Bernard Baars’ “Global Workspace Theory”. This offers an
intuitive way to think about the various notions that float around psychology
circles such as attention, working memory, ‘binding problem’ in perception, and
not least of all, consciousness. The essential premise of the theory is that various
information processing modules in the brain that operate independently and
unconsciously compete in order to transmit the output of their processes into
the working memory module, success of which leads to those outputs being
globally broadcast to the whole brain in order to recruit processing from
unrelated modules, such as speech for reportability, motor function for
incorporation into volitional strategies, perhaps multimodal areas for binding of
percepts, etc. On this account, consciousness is just whatever activity has
made it into the working memory as well as being globally broadcast. I am not
yet 100% satisfied by this account however. It seems to address the question by
means of offering a sort of network framework; in other words, it is answering
the ‘easy problem’ but does not seem to tackle the ‘hard problem’ at all. The
former of these deals with how brain activity gives rise to ‘access
consciousness’, that which can be used by the rest of the brain, whereas the
latter concerns itself with ‘phenomenal consciousness’, that which forms the
qualitative feel of experience – what philosophers call ‘qualia’. So, while
Baars’ theory may satisfactorily give a mechanistic account of the processing
that takes place in the brain that gives rise to an integrated network of
information, it seems to dodge the deeper question of why this particular form
of processing is accompanied by awareness, that ephemeral ‘knowing’ of which we
cannot really speak, which remains here unaddressed. Of course, I run the risk
of blaspheming against the current ideology of the material metaphysic that
dominates most modern intellectual thought. Nevertheless, I do so from an
intuition of the inadequacy of naturalist science. Whether or not the hard
problem is even solvable in principle I cannot say. Yet still, I maintain that
the acknowledgement of this problem mandates a radically revised ontology.

I must insert here, despite what
has been said above, the fact that I am gradually beginning to lean towards a
more eliminitavist position on the ‘hard problem’ debate. That is to say, I do
have moments of skepticism towards these so-called ‘intuitive’ accounts that
postulate the existence of a hard problem. It may be that the workspace account
exhausts all there is to consciousness and that it is precisely the integration
of a percept into the global workspace that brings about this phenomenal
experience of its ‘qualia’. Either deeper introspection or hard science may
eventually elucidate this extremely subtle question, but for now it remains an
utter mystery.

Attention:

This
consideration brings me to another favorite topic of mine in neuroscience and
psychology. This is the phenomenon that is colloquially as well as academically
known as attention. At first glance, it may seem like there is a significant
overlap, if not synonymy, between this concept and consciousness. However,
closer scrutiny reveals that while the two are related, it remains advantageous
to maintain a conceptual distinction between them. Attention can be thought of
as the selective mechanism that decides which of the vast array of incoming
sensations and internal operations are consciously experienced. In the
workspace framework, it is the effect of the mechanisms that collectively
determine which information processing module ‘wins’ the battle to relay its
message into the working memory, which subsequently relays the message globally.
As such, it is sometimes symbolized as a ‘spotlight’, which scans across the
various actors and/or props on a theater stage, selecting as it does which of
these is to become the center of focus for the audience. There may be a slight
circularity in this metaphor, since attention is itself the mediator of its own
symbol, but it suffices for the purposes of illustration.

Many
theories have been proposed as to the functioning of this attentional
spotlight, and there are several subdivisions of the concept that I will
briefly go over here. First, attention is divided into top-down and bottom-up
forms. The former, also known as endogenous attention, is the form of attention
that is at play when we consciously select what to attend to on the basis of
goal-directedness; hence, top-down. Bottom-up attention, conversely, is at play
when some highly salient stimulus from the environment captures our attention
and draws our processing resources to it, such as when you hear your name
spoken and it seems to ‘pop’ into your awareness uninvited. So, while both are
selection mechanisms, one operates in a purely automatic fashion based entirely
on the perceptual saliency of stimuli, perhaps as an evolutionarily hard-coded
adaptive system, whereas the other operates in a volitional fashion and is
based on the goals and intentions of the agent.

An
immediate question that arises regards the extent to which attention’s
selective power can exclude distractors from reaching and interfering with the
task that is being performed at the center of the ‘spotlight’. Nillie Lavie’s
theory of perceptual load offers an elegant solution to this question. Her
claim is that there are multiple factors that play a role in determining the
selectivity of attention and its ability to protect against intrusion by task-irrelevant
distractors. These are the so-called perceptual load and the working memory
load. The effects of these are inversely proportional to each other, where
loading the former exhausts perceptual capacity which hence cannot be used to
process distractors, whereas loading the latter interferes with the brain’s
ability to maintain current goals in order to exert its top-down attentional selection,
hence causing greater intrusion by distractors. This account relies on the
concept of perceptual resources, of which there may remain some that are not
used in the processing of the central task, and which may ‘spill over’ and
automatically process task-irrelevant stimuli. 

Another of
my favorite subjects is meditation, and this is directly related to attention
insomuch as it is an activity whose purpose is to train the attentional focus
of the meditator’s brain. By so doing, it makes the selective function of
attention stronger, causing more processing resources to be utilized in the
processing of the central task. This may be because it frees up working memory
capacity, which therefore will reduce the amount of distractor interference
because of the availability of resources to effectively select stimuli. I have
noticed from my meditations that the beginnings are usually characterized by an
effusive scattering of my thoughts from one topic to the next and an extreme
difficulty at keeping the attentional spotlight fixed on the object of the
meditation, which in this case would be the breath. As the sit progresses, I am
more and more able to filter out the competing distractors and keep the flame
unwavering, and this may just be because of the freeing up of space in the
working memory. Alternatively, it may also be because of the strengthening of
mechanisms that bring the desired object into the working memory and the
weakening of those same mechanisms for irrelevant objects. However, I currently
favor the first account because it is more in line with the subjective
experience of meditation where what is in the forefront of the ‘theater of the
mind’ seems to become uncluttered. Another way to think about this is to posit
that the non-meditator’s attention fluctuates between a variety of stimuli
including the centrally relevant task as well as other interfering stimuli. In
other words, many modules are ‘winning’ the battle to transmit their outputs to
the working memory, and this causes the frequent distraction. The meditator, on
the other hand, has more stringent selection criteria for the conditions under
which outputs can be transmitted into the working memory. This may turn out to
be the exact same situation that leads to the freeing up of the working memory
capacity.

Directions:

By studying
the body representation mechanisms of the brain, I hope to somehow be approaching
the issue of self-representation, which in turn taps into the issue of self-consciousness.
As it currently stands, I am only looking at a very specific perceptual
phenomenon, namely the rubber hand illusion. Eventually, I hope to be able to
examine how the consciousness of the illusory percept is generated. This may
possibly account for why some participants do not experience the illusion,
despite showing strong proprioceptive effects. Perhaps I can demonstrate some
dissociation between dorsal and ventral streams in the processing of the
illusion. Additionally, the effect of attention on the rubber hand illusion may
prove to be something worth investigating. It may be that an attentional
deficit is responsible for the failure to experience the illusory percept. Finally,
if the holistic integrated percept of the body is generated through a process
of causal inference, what additional constraints need to be implemented in
order for the self/other discrimination that is fundamental to our sense of
selfhood? The causal inference rules used here are the same that the brain uses
to generate its perception of all impinging sensations, whether they originated
from the body or otherwise. Therefore, there must be some additional rules that
are instantiated in the specific case of body perception.

My current
research simply aims to elucidate further the link between proprioceptive localization
of the finger under conditions of visual occlusion and experience of the rubber
hand illusion. Several recent studies have shown that proprioceptive drift may
not in fact be a reliable behavioral proxy of the illusion and may simply occur
as a natural result of visual occlusion. My research seems to tentatively
support this idea, but the analysis that I will run on the data will hopefully reveal
more than has been previously shown thanks to an additional manipulation that I
am introducing. The goal of this is to eventually find a way to mathematically
model the processes that are taking place in the brain when it is performing visual-proprioceptive
integration, the hope being that a natural explanation for drift and bias will emerge
from the equations. At a later stage, it may become possible to model the
trimodal integration that takes place between vision, proprioception, and
touch, the result of which is the rubber hand illusion. However, at the moment,
this is an impossible task as there are too many free parameters and too few
variables that can be reliably measured in order to constrain the model by fitting
it to collected data. But science progresses step-by-step, and so I must remain
patient and persistent in my attempts to arrive at clever designs that can
answer some or all of the questions and issues discussed above.