Synaptic facilitation requires paired activation of convergent pathways in the neocortex

In associative learning, the activated neurones undergo a variety of concomitant functional alterations—increases or decreases of firing activity1–4 and modifications of membrane potential or resistance5–8 and of synaptic responsiveness9–11 . Synaptic transmission which can be strengthened only when there is paired activity in two pathways is of particular interest in relation to mechanisms for associative learning12,13. For the neocortex, there are few observations of the plastic changes, induced by conditioning procedures, in the effectiveness of individual synapses14–17. We now report that various regimes with joint stimulations of convergent excitatory pathways on to intracellularly recorded neurones in the motor cortex of the cat result in synaptic facilitation lasting for up to 30 min.

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