Reduced variability of ongoing and evoked cortical activity leads to improved behavioral performance

Abstract

Sensory responses of the brain are known to be highly variable, but the origin and functional relevance of this variability/nhave long remained enigmatic. Using the variable foreperiod of a visual discrimination task to assess variability in the/nprimate cerebral cortex, we report that visual evoked response variability is not only tied to variability in ongoing cortical/nactivity, but also predicts mean response time. We used cortical local field potentials, simultaneously recorded from/nwidespread cortical areas, to gauge both ongoing and visually evoked activity. Trial-to-trial variability of sensory evoked/nresponses was strongly modulated by foreperiod duration and correlated both with the cortical variability before stimulus/nonset as well as with response times. In a separate set of experiments we probed the relation between small saccadic eye/nmovements, foreperiod duration and manual response times. The rate of eye movements was modulated by foreperiod/nduration and eye position variability was positively correlated with response times. Our results indicate that when the time/nof a sensory stimulus is predictable, reduction in cortical variability before the stimulus can improve normal behavioral/nfunction that depends on the stimulus.