SENSORY EXPECTATIONS AND ANTI-HEBBIAN SYNAPTIC PLASTICITY IN CEREBELLUM-LIKE STRUCTURES

Cerebellum-like sensory structures in different groups of fish have be en shown to generate a negative image of predictable features of the s ensory input. We show here that anti-Hebbian plasticity is present at the synapse between parallel fibers and Purkinje-like cells which coul d mediate the generation of these negative images. We also show that t his synapse is capable of bidirectional changes in synaptic efficacy w ith the direction of change depending on the precise temporal relation of presynaptic input and postsynaptic spike during pairing. Parallel fiber-evoked EPSPs are depressed after pairings in which the EPSP begi ns between 0 and 60 ms before the postsynaptic spike but are enhanced at other delays, including those in which the postsynaptic spike occur s just before the EPSP.