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Lyndon Duong, Sebastien Tremblay, Adam Sachs, Julio Martinez-Trujillo; Correlation between the effects of attention and response normalization in prefrontal area 8A neurons is cell type dependent.. Journal of Vision 2015;15(12):1061. doi: 10.1167/15.12.1061.
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© ARVO (1962-2015); The Authors (2016-present)
Many visual neurons lower their response rates to a stimulus in the receptive field when other stimuli are added inside or outside their receptive field. This phenomenon has been proposed to be the result of a canonical normalization mechanism that acts across multiple brain areas and has been reported to correlate with visual attentional response modulation in extrastriate visual neurons. We recorded neural activity in prefrontal area 8A, an area associated with selective visual attention, of two macaca fascicularis using chronically implanted multielectrode arrays during two task conditions. In one condition, the animals were presented with four identical grating stimuli, each positioned in one quadrant of the visual field while fixating on a central dot. In the second condition, one grating was initially presented followed by the onset of the remaining three stimuli. The position of the first grating (the target) varied between trials. Animals had to make a saccade to the target when that grating changed orientation. The majority of our visually-tuned single units showed a lower response when four stimuli were presented relative to the sum of individual responses to each single stimulus (mean normalization index = 0.72). These units also showed a strong attentional modulation (mean attentional index = 0.41). Importantly, units with stronger normalization showed the strongest attentional modulation (r=0.19; p< 0.05). We further classified attention-tuned units depending on the hemifield which showed the strongest visual response relative to the recording site. Ipsilateral neurons showed negative correlations between normalization and attention when the animals switched attention whereas contralateral neurons showed positive correlations. Finally, spike-count correlations were higher between ipsilateral than between contralateral neurons. These results demonstrate that in PFC circuitry, normalization and attention are linked, and that neurons here may perform different computations during attention allocation depending on their spatial tuning.
Meeting abstract presented at VSS 2015
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