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 When the Brain Remembers but the Patient Doesn’t

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Date posted: 17/07/2011

As the core principles of neurocomputation adhere to, the brain is all there is. It's circuitry is responsible for every aspect of a person's thoughts, feelings, behaviour. The neurons and glia cells networked together control every aspect of perception and data processing.

Thus, if there is damage to the brain this circuitry is disrupted. Circuits broken and new ones formed. It can cause a person to lose skills, or memories that were once sharp to decay into nothing. However, such brain damage is also a wonderful tool for diagnosing the structure of the brain; monitoring how such damage in a specific area, alters behaviour and processing abilities.

This case is no different. Reported in the July 2011 issue of Elsevier’s Cortex, findings by Dr Stéphane Simon and collaborators in Professor Alan Pegna’s laboratory at Geneva University Hospital, shed light on the object recognition system of the brain, by studying the brain damage in a patient with prosopagnosia.

Prosopagnosia is Greek in origin, it basically means “face-inability”, and refers to a visual identification condition in which sufferers lose the ability to recognise faces, or at least have it severely impaired. This limits their ability to pick individuals out of a crowd, or recognise loved-ones as separate from people with similar shaped faces. Its an ability learned by infants in their first six months of age, and is an ability that would be vital to machine vision systems wishing to quickly and reliably identify individuals.

Currently, sufferers of prosopagnosia are taught to use these same strategies as employed by current machine vision systems, in order to function day-to-day. They use piecemeal recognition, studying a face piece by piece to work out who it is. Or they go by other behaviometric data such as the types of clothes worn, gait and mannerisms to work out who the individual is.

Such systems are time-consuming and at times socially awkward. A greater understanding of the area of the brain concerned – the fusiform gyrus – would aid in unravelling how face recognition works so quickly and seemingly effortlessly in humans, and how we could duplicate this ability both for those who have lost it and for artificial systems to use.

Dr Stéphane Simon and team worked with their patient, and utilised both fMRI and EEG measures of her brain activity in the fusiform gyrus and other areas to determine what was going on when she looked at people's faces. The answers were a little surprising.

Despite the fact that the patient could not recognize any of the famous faces, her brain activity responded to the faces that she would have recognized before the onset of her condition.

In other words, the processing for face recognition is not taking place where we traditionally associate it with, and the fusiform deals with integration of the data from multiple sources. Or to put it a third way, in the words of Professor Pegna, one of the researchers involved. “The results of this study demonstrate that implicit processing might continue to occur despite the presence of an apparent impairment in conscious processing. The study has also shed light on what is required for our brain to understand what we see around us. Together with other research findings, this study suggests that the collaboration of several cerebral structures in a specific temporal order is necessary for visual awareness to arise.”

See the full Story via external site: www.elsevier.com



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