详细记录  
题名:Experience-dependent representation of visual categories in parietal cortex
作者:David J. Freedman1 and John A. Assad1
来源:Nature 443, 85-88(7 September 2006) | doi:10.1038/nature05078; Received 5 May 2006; Accepted 13 July 2006; Published online 27 August 2006
URL :http://www.nature.com/nature/journal/v443/n7107/full/nature05078.html
日期:060930
摘要:Categorization is a process by which the brain assigns meaning to sensory stimuli. Through experience, we learn to group stimuli into categories, such as `chair`, `table` and `vehicle`, which are critical for rapidly and appropriately selecting behavioural responses1,2. Although much is known about the neural representation of simple visual stimulus features (for example, orientation, direction and colour), relatively little is known about how the brain learns and encodes the meaning of stimuli. We trained monkeys to classify 360° of visual motion directions into two discrete categories, and compared neuronal activity in the lateral intraparietal (LIP) and middle temporal (MT) areas, two interconnected brain regions3 known to be involved in visual motion processing4,5,6. Here we show that neurons in LIP—an area known to be centrally involved in visuo-spatial attention7,8,9, motor planning10,11,12,13 and decision-making14,15,16—robustly reflect the category of motion direction as a result of learning. The activity of LIP neurons encoded directions of motion according to their category membership, and that encoding shifted after the monkeys were retrained to group the same stimuli into two new categories. In contrast, neurons in area MT were strongly direction selective but carried little, if any, explicit category information. This indicates that LIP might be an important nexus for the transformation of visual direction selectivity to more abstract representations that encode the behavioural relevance, or meaning, of stimuli.

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