Primary changes of membrane currents during retention of associative learning.

A single identified neuron was repeatedly isolated by axotomy from the central nervous system of the nudibranch mollusk Hermissenda crassicornis. An early voltage-dependent outward K+ current of this neuron was reduced and more rapidly inactivated for animals previously trained with paired but not randomized light and rotation. Since this current change can affect interneuron and motorneuron output via known synaptic pathways, it helps explain a long-lasting behavioral change that shows the defining features of vertebrate associative learning.