Fig. 5: Dependence of spiking irregularity on the behavioral and cognitive state.

a Attention task performed by monkeys during V4 recordings. Monkeys detected an orientation change in one of four peripheral grating stimuli, while an attention cue (short white line) indicated which stimulus was likely to change. Monkeys reported the change with a saccade to the stimulus opposite to the change (black arrow). The cued stimulus was the target of covert attention, while the stimulus opposite to the cue was the target of overt attention. The dashed circle indicates the receptive field location of the recorded neurons (V4 RF). b Task conditions (left). On cue-RF trials (green frame), the attended stimulus (yellow circle) was in the RF of recorded neurons. On cue-opposite trials (orange frame), antisaccades were directed to the RF stimulus (black arrow). On cue-orthogonal trials (pink and purple frames), neither the attended stimulus nor the saccade target was in the RF. The scatter plots show estimated ϕ for every pair of task conditions. Each dot represents one V4 neuron. c Decision-making task performed by monkeys during PMd recordings. Monkeys discriminated the dominant color in a checkerboard stimulus composed of red and green squares and reported their choice by touching the corresponding target (upper panels). Task conditions varied by the response side indicated by the stimulus (left versus right) and stimulus difficulty controlled by seven coherence levels c1 through c7 (lower panels). d The scatter plots show estimated ϕ for each pair of coherence levels, combined across chosen sides. Each dot is one PMd neuron. e The scatter plot shows estimated ϕ for right versus left choice trials, combined across coherence levels. Each dot is one PMd neuron. f Histogram across PMd neurons of the modulation index of ϕ estimated during the fixation (when targets were visible) and decision epochs of the task. The triangle marks the median modulation index, which is significantly greater than zero (***p = 3 ⋅ 10⁻⁷, n = 262, one-sided Wilcoxon signed-rank test). Source data are provided as a Source data file.