Activity-Dependent Regulation of Cortical Activity

Circuit dynamics arise from the complex interplay between synaptic connections and the intrinsic electrical properties of individual neurons. Both of these features are responsive to, and presumably regulated by, a neuron's history of activity. Here we examine how long-term activity deprivation affects the properties of neocortical neurons using electrophysiological methods. Whole-cell patch recordings were obtained from pyramidal neurons in rat visual cortical cultures. Activity was blocked in test cultures for two days prior to experiments by incubation in tetrodotoxin (TTX). After the TTX was removed, pronounced rebound phenomena were observed: ionic conductances were modulated so as to increase neuronal excitability substantially, and the strengths of excitatory synaptic connections were similarly increased. Both of these activity-dependent phenomena may be important in preserving the stability and sensitivity of neural circuits, for example during the long-lasting fluctuations in input that can accompany development and learning.

 

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