Dependence of Cortical Plasticity on Correlated Activity of Single Neurons and on Behavioral Context

TLDR

Studying cellular mechanisms of learning in behaving mammals has been hindered by the difficulty of intracellular recordings in awake animals. The study aimed to assess how the firing of one neuron influences another by cross‑correlating their spike times in behaving monkeys. The authors cross‑correlated spike times of neuron pairs to quantify their functional connections. Co‑firing within a brief window potentiated functional connections, while preventing simultaneous firing depressed them, and these changes were strongly modulated by the behavioral context, indicating that temporal contingency alone is insufficient for cortical plasticity without behavioral relevance.

Abstract

It has not been possible to analyze the cellular mechanisms underlying learning in behaving mammals because of the difficulties in recording intracellularly from awake animals. Therefore, in the present study of neuronal plasticity in behaving monkeys, the net effect of a single neuron on another neuron (the "functional connection") was evaluated by cross-correlating the times of firing of the two neurons. When two neurons were induced to fire together within a short time window, the functional connection between them was potentiated, and when simultaneous firing was prevented, the connection was depressed. These modifications were strongly dependent on the behavioral context of the stimuli that induced them. The results indicate that changes in the temporal contingency between neurons are often necessary, but not sufficient, for cortical plasticity in the adult monkey: behavioral relevance is required.