Task-dependent representations of stimulus and choice in mouse parietal cortex

Gerald N Pho,Benjamin Crawford,Jonathan Woodson,Mriganka Sur,Michael J Goard

doi:10.1038/s41467-018-05012-y

Abstract

The posterior parietal cortex (PPC) has been implicated in perceptual decisions, but whether its role is specific to sensory processing or sensorimotor transformation is not well understood. Here, we trained mice to perform a go/no-go visual discrimination task and imaged the activity of neurons in primary visual cortex (V1) and PPC during engaged behavior and passive viewing. Unlike V1 neurons, which respond robustly to stimuli in both conditions, most PPC neurons respond exclusively during task engagement. To test whether signals in PPC primarily encoded the stimulus or the animal’s impending choice, we image the same neurons before and after re-training mice with a reversed sensorimotor contingency. Unlike V1 neurons, most PPC neurons reflect the animal’s choice of the new target stimulus after re-training. Mouse PPC is therefore strongly task-dependent, reflects choice more than stimulus, and may play a role in the transformation of visual inputs into motor commands.

Highlights

The posterior parietal cortex (PPC) has been hypothesized to play a key role in at least some types of decision tasks in both primates[1,2] and in rodents[3,4,5]
We focused on target-preferring neurons, as these represented the vast majority of responses in PPC, and restricted analysis to those imaging fields and behavioral sessions in which the mouse committed at least five False Alarm (FA) trials (V1, n = 1053 cells from 16 fields; PPC, n = 3034 cells from 21 fields)
We developed a simple head-fixed visual decision task for mice with separate stimulus and response epochs, and used population imaging of single neuron responses to investigate the role of PPC in perceptual decisions

Summary

Introduction

The posterior parietal cortex (PPC) has been hypothesized to play a key role in at least some types of decision tasks in both primates[1,2] and in rodents[3,4,5]. Some argue that rodent PPC may be more homologous to extrastriate cortex in processing sensory signals that are accumulated elsewhere for decision-making[10] Both anatomical projection studies[11,12], as well as functional mapping studies[13,14] indicate that PPC may overlap with or contain a group of retinotopically-organized extrastriate areas that are rostral to primary visual cortex (V1). A third, alternative possibility is that PPC may play a role in the mapping of visual stimuli to motor commands. If this were the case, one may expect that activity in PPC would be highly task-dependent, reflecting the animal’s decision depending on learned sensorimotor contingencies. Our results are consistent with a role of the mouse posterior parietal cortex in transforming visual information to motor commands during perceptual decisions

Methods

Results

Conclusion