Body
perception is a popular topic of research at the moment. From small regions in ‘high level’ visual parts
of the brain that seem statistically more enthusiastic to see pictures of your
body from allocentric visual perspectives than egocentric. To emotional bodies that can be perceived but
not seen, to expert bodies and avatars. One of the underlying assumptions of some of the body perception research is that there is a neural representation of a ‘self' and an ‘other’. In visual perception, the body is often conceived as an object, a high level animate object, but an object nonetheless
Interpretations
of neuroimaging research, that have identified functionally distinct regions in
the visual parts of the brain that respond selectively to faces and separately
to headless bodies vary considerably. From the more functionally conservative
interpretation; that these are groups of neurons that play some role in recognizing
the human form, to the all inclusive accounts; that they are integral parts of
a perception action system, and the more conceptually far reaching and
exciting; they function to distinguish a ‘self ‘from an ‘other’. On all
accounts the body is represented in the brain.
What about
bodies during social interaction? What basic communicative functions do
bodies fulfill?
Hands are implicitly associated with expression, communication and
purposeful action. Of the myriad of hand gestures that humans use pointing is
one of the most common and powerful in its role as a visual referent that
directs joint attention. There is a rare and bizarre neuropsychological
pointing disorder called Heterotopagnosia. People with specific neurological
damage are unable to point at another person’s body parts when prompted. They
retain the ability to grasp at the body parts and to point at non-body objects
placed on the person, and can perfectly describe the body parts and the action,
but remain unable to perform it. Often they will point at their own
body parts instead. Implying a disruption in distinguishing a self
(my body) from other (your body).
Up until
recently, a disruption of the ‘body schema’, or mental representation of the
other person’s physical form has been the primary explanation for this
syndrome. While it is likely that some form of body representation must be
accessed while pointing at another person’s body, a French research group showed that the
condition is specific to the object of interest being a living human. Performance
improves when prompted to point at a manikin or a figure of a
human. While I don’t think ethics would be overly enthused, I wonder
what the response to a cadaver would be?
They argue
that Heterotopagnosia cannot be explained solely as a deficit in body
representation. Highlighting the communicative capacity of the live human body
as an essential characteristic of the deficit. Not only do we need to visually
and spatially locate certain parts of the body of another, the body is also a
vehicle for communication and it is the communicative power of the human form
as a target interacting with the communicative function of pointing that seems
to provide a more comprehensive account of the disorder.
The
syndrome also ‘reveals
a crucial difference between dyadic and triadic interactions'. Other object oriented
gestures like grasping reflect dyadic relationship between the ‘I’ and the
target of the action. The ability to grasp at the persons body is
maintained in Heterotopagnosia while pointing concerns a triadic relationship of communication where
“I” direct “you” to the object “it” or the person “him/her.
Rather
than bodies as isolated objects, in this research bodies are actively engaged
in their environment with other bodies. The explanation for the
underlying causes of Heterotopagnosia have shifted away from a purely
'mind in skull' internal representational model. Rather than the body
being viewed as another type of object, more emphasis is placed on the communicative role of
the body in a particular social situation.
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