Sunday, 23 February 2014

My Body, Your Body, Whose Body?

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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