Spatiotemporal Divergence between Intrinsic and Evoked Cortical Activity Predicts Visual Detection

Abstract

The threshold for sensory detection varies with fluctuations in intrinsic cortical activity. When stimulus encoding cortical populations are more excitable, stimuli elicit stronger neural responses that are more likely to be detected. However, the detection of a stimulus is also more likely when cortical populations are less excitable because there is less background “noise.” Therefore, it is unclear how the variable states of cortical activity interact to impact sensory detection. We hypothesize the answer depends on the spatiotemporal structure of intrinsic activity states across stimulus encoding and nonencoding populations. To test this, we examined intrinsic and target-evoked population activity across cortical Area MT in common marmosets ( Callithrix jacchus ; one male and one female) while they performed a threshold visual detection task. We compared detection performance based on target-evoked responses and the state of intrinsic activity in the larger surrounding population. We find that the intrinsic activity in the surrounding, nonencoding population predicted trial-by-trial detection performance better than the population encoding the target-evoked response. Furthermore, we find that the detection performance of the monkey was best predicted by the divergence in activity between the encoding and surrounding nonencoding population. These findings suggest that, rather than a source of noise or irrelevant to sensory processing, the distributed spatiotemporal state of intrinsic activity directly influences how sensory signals are represented in cortical populations and can influence perceptual thresholds in visual detection.