Wesleyan University Adaptive Sensory Filtering in the Cerebellar-like Mechanosensory Nucleus of the Hindbrain in Raja Erinacea

In all cerebellar-like structures, a multipolar principle neuron has spiny apical dendrites synapsing a superficial parallel fiber layer but also receives a second functionally and anatomically distinct input. The cerebellar-like first-order nuclei in the electrosensory system of teleost and non-teleost fishes filter reafference and other predictable stimuli out of the system. The mechanism by which this occurs can be described by the adaptive filter model proposed by Montgomery and Bodznick (1994). A parallel fiber information array and primary sensory afferents converge onto the principal neuron, with coincident activation inducing anti-Hebbian plasticity at the molecular layer parallel fiber synapses. This present study addresses whether the same adaptive filter model can predict the operation of the cerebellar-like medial nucleus in the lateral line system of the little skate, Raja erinacea. Single-unit, extracellular recording techniques were used in vivo to study the principal neurons and measure learned compensations for an external mechanosensory stimulus made predictable by time-locking it to the natural ventilation cycle. That changes in AEN activity patterns were predicted by the adaptive filter model suggest that the mechanism is not just a specialization of the electrosense, and it may be underlying stimulus response conditioning in the mechanosensory system as well. By similar logic, the adaptive filter model may generalize to other cerebellar-like structures, and even to the cerebellum itself.