Thursday, April 26, 2018 - 12:00pm to 1:00pm
Neurological Institute Alumni Auditorium
Neuronal activity in cerebral cortex shows many attention-related changes that might contribute to improved behavioral performance: neurons have stronger responses to attended stimuli and effectively mask unattended stimuli within their receptive field; nearby neurons have activity that is less correlated; and the gamma power in extracellular potentials increases. About ten years ago, it became widely recognized that attention-related changes in neuronal responses are closely linked to a response-integration mechanism known as normalization. However, the relationship between attention and normalization in determining neuronal responses has not been clear. We have examined this relationship by recording responses from individual neurons in visual cortex of trained, behaving rhesus monkeys. We have taken advantage of different stimulus configurations that produce, or do not produce, normalization. The only neuronal correlate of attention that survives the removal of normalization is a modest increase in the strength of neuronal responses. The masking of unattended stimuli, reductions of correlated activity and increase of gamma power all depend having robust normalization. With robust normalization, those same phenomena can be seen when attention is removed from the picture and replaced by simple changes in stimulus strength. Overall, these results suggest that the immediate effect of attention is a modest modulation of sensory responses, and that the more striking signatures that have been previously attributed to attention are better viewed as signatures of normalization mechanisms that lie downstream.
Dr. John Maunsell
University of Chicago