Pascal Fries | “Learning of stimulus probability and reward value in early visual cortex”
Theoretical and computational neuroscience \ Manfred Eigen lecture theatre
Natural viewing entails repeating stimuli, whose processing could be optimized. Repetition typically leads to reduced neuronal firing rates and, as I will show, to increased neuronal gamma-band synchronization in visual cortex, likely preserving postsynaptic impact. These gamma increases are stimulus-specific, do not transfer to other stimuli, persist for minutes, occur with artificial and natural stimuli, and are observed in both non-human primates and humans. Moreover, stimulus-induced gamma reflects the optimal Bayesian estimate of a stimulus’ occurrence frequency. Finally, repetition enhances gamma only if the first presentation was rewarded; otherwise gamma is reduced, suggesting a medium-term memory of stimulus-reward contingency.