Variability in neuronal responses to identical stimuli is frequently correlated across a population. Attention is thought to reduce these correlations by suppressing noisy inputs shared by the population. However, even with precise control of the visual stimulus, the subject’s attentional state varies across trials. In 2016, we put out the hypothesis that such fluctuations in attentional state could be a cause for some of the correlated variability observed in cortical areas. To address this question empirically, we designed a novel paradigm that allows us to manipulate the strength of attentional fluctuations.
In the new paper just published in Nature Communications, we recorded from monkeys’ primary visual cortex (V1) while they were performing this task. We found both a pronounced effect of attentional fluctuations on correlated variability at long timescales and attention-dependent reductions in correlations at short timescales. These effects predominate in layers 2/3, as expected from a feedback signal such as attention.