Functions of Shallow vs. Deep Theta-Nested Gamma in Object Recognition

Abstract

Using a network of excitatory pyramidal cells and inhibitory interneurons with fast and slow GABA(A) kinetics, we have successfully reproduced our recent experimental observations from local field potential and multiunit activity recordings from the sheep's inferior temporal cortex during learning of visual discrimination tasks. Both experimental and numerical results showed that following learning, theta wave amplitude is significantly increased and its phase is more highly correlated with the amplitude of gamma wave during stimulus presentation. The increased correlation between the theta phase and the gamma amplitude is a consequence of theta-nested gamma. Importantly, we have used the model to show that learning effects can be reproduced simply by altering the sensitivity of NMDA receptors and that the resultant shallowing of theta -nested gamma potentiates responses made by downstream neurons.