Developmental synaptic pruning in the olivo-cerebellar circuit sculpts predictive processing

Synaptic pruning, especially in the cerebellum, is a dominant process of circuit assembly, known to eliminate a large proportion of synapses formed during development. Yet, very little is understood about how the drastic elimination of a large number of synapses affects circuit computation and behavior. Zebrafish are an ideal model organism to address this question as they undergo cerebellar maturation while navigating complex aqueous environments. Here, we first establish the timelines of synaptic pruning in the olivocerebellar climbing fiber (CF) to Purkinje neuron (PN) synapses of larval zebrafish. We then show that during this window, CF to PN inputs show improvements in encoding of sensori-motor mismatches, tuning of sensory representations and more robust predictive signals. Concomitant with these changes, larval visuomotor behaviors are faster and better adaptable to current sensory input. We propose that developmental synaptic pruning makes circuits fit for complex computations such as predictive processing and contributes to improved behavioral performance.