Temporal Dynamics of Cortical Adaptation

Abstract

Adaptation of cortical neurons in response to prior stimulus history and the timecourse of recovery from adaptation were investigated at the level of action potentials using the juxtacellular single-cell loose-patch recording paradigm in the barrel cortex of juvenile rats. An experimental protocol that paired adaptor and test deflections of the principal whisker for a given neuron was applied in two phases of the study. Experiment 1 involved two adaptor conditions, differentiated by the duration of the adaptor stimulus, presented with a limited range of four adaptor-test temporal separations. Experiment 2 involved a single adaptor condition followed by an expanded range of adaptor-test temporal separations. Experiment 1 demonstrated that the time-course for recovery from adaptation was dependent on the duration of the adaptor stimulus. Experiment 2 demonstrated that recovery of action potential responses in the cortical population follows a sigmoidal pattern, in contrast to the exponential decay of adaptation at the post-synaptic potential level. Data from both experiments provided evidence for adaptation increasing trial-to-trial variability of neuronal responses to stimuli as well as reducing discriminability between the presence or absence of a test stimulus of similar characteristics to the adaptor stimulus. Morphological recovery was achieved for a sample of neurons, and case studies of the relationship between neurons’ morphology and functional behaviour provide insights for further investigations into adaptation and functional diversity within the cortex. Show more