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Brain circuits for visual categorization identified

London , Mon, 16 Jan 2012 ANI

London, Jan 16 (ANI): A team of scientists including one of Indian-origin has spotted an area in the brain, which is involved in the visual categorization process.

 

Organizing the chaos of the surrounding world into categories is one of the brain's key functions. For instance, the brain can almost immediately classify a broad range of four-wheeled vehicles into the general category of "car," allowing a person to quickly take the appropriate action.

 

"The number of decisions we make per minute is remarkable," said David Freedman, PhD, assistant professor of neurobiology at the University of Chicago.

 

"Understanding that process from a basic physiological perspective is bound to lead to ways to improve the process and to help people make better decisions.

 

"This is particularly important for patients suffering from neurological illnesses, brain injuries or mental illness that affect decision making."

 

For the study, Freedman and graduate student Sruthi Swaminathan conducted the first direct comparison of prefrontal cortex (an area that is typically associated with higher level cognitive functions) and parietal cortex during categorization tasks.

 

Monkeys were taught a simple game in which they classified dots moving in different directions into one of two categories. The subjects were shown two sets of moving dots one second apart, then held or released a joystick based on whether the two stimuli belonged to the same category or different categories.

 

During the task, scientists recorded neural activity in PFC and a region of the parietal cortex called LIP (Lateral Intraparietal Area). Neurons in both areas changed their activity according to the learned categories; for example, increasing firing for one category and decreasing for the other.

 

However, category-specific neurons in LIP exhibited stronger and faster (by about 70 milliseconds) changes in activity during the task than those recorded from PFC.

 

"The relative timing of signals in the two brain areas gives us an important clue about their roles in solving the categorization task. Since category information appeared earlier in parietal cortex than prefrontal cortex, it suggests that parietal cortex might be more involved in the visual categorization process, at least during this task," Freedman said.

 

More evidence for the primacy of parietal cortex was provided by an experiment where scientists threw their subjects a curveball. The subjects were required to make a decision about which category the ambiguous stimuli belonged to, and once again LIP neurons corresponded to that decision more closely than PFC.

 

The study will be published in the journal Nature Neuroscience. (ANI)

 


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