Distributed sensory coding by cerebellar complex spikes in units of cortical segments.

Takayuki Michikawa,Ryo Kimizuka,Hideo Yokota,Akinobu Shimizu,Takahiro Ishikawa,Atsushi Saito,Satoshi Kuroki,Shinji Kakei,Atsushi Miyawaki,Shigeyoshi Itohara,Takamasa Yoshida

doi:10.1016/j.celrep.2021.109966

Abstract

Sensory processing is essential for motor control. Climbing fibers from the inferior olive transmit sensory signals to Purkinje cells, but how the signals are represented in the cerebellar cortex remains elusive. To examine the olivocerebellar organization of the mouse brain, we perform quantitative Ca2+ imaging to measure complex spikes (CSs) evoked by climbing fiber inputs over the entire dorsal surface of the cerebellum simultaneously. The surface is divided into approximately 200 segments, each composed of ∼100 Purkinje cells that fire CSs synchronously. Our invivo imaging reveals that, although stimulation of four limb muscles individually elicits similar global CS responses across nearly all segments, the timing and location of a stimulus are derived by Bayesian inference from coordinated activation and inactivation of multiple segments on a single trial basis. We propose that the cerebellum performs segment-based, distributed-population coding that represents the conditional probability of sensory events.

Highlights

The cerebellum has a role in motor control (Ito, 1984) and perceptual processing (Baumann et al, 2015)
Identification of olivocerebellar segments We employed yellow cameleon 2.60 (YC2.60), a genetically encoded Ca2+ sensor based on fluorescent resonance energy transfer (FRET) between cyan- and yellow-emitting fluorescent proteins (Miyawaki et al, 1997; Nagai et al, 2004) to detect dendritic Ca2+ increases accompanied by complex spikes (CSs)
YC2.60 was expressed in Purkinje cells (PCs) using an adenoviral transduction method (Horikawa et al, 2010; Yamada et al, 2011)

Summary

Introduction

The cerebellum has a role in motor control (Ito, 1984) and perceptual processing (Baumann et al, 2015). It receives information about the external world and the state of the body on a moment-to-moment basis (Gibson et al, 2004; Glickstein, 1998). Purkinje cells (PCs) are the sole output of cortical neurons, which receive two types of excitatory inputs: mossy fibers (MFs) relayed to granule cells and climbing fibers (CFs) (Figure S1A). A PC receives inputs from granule cells and changes the firing rate of simple spikes (Figure S1A)

Methods

Results

Discussion

Conclusion