Perceptual decisions and oculomotor responses rely on temporally distinct streams of evidence

Matteo Lisi,Joshua A Solomon,Michael J Morgan

doi:10.1038/s42003-022-03141-1

Abstract

Perceptual decisions often require the integration of noisy sensory evidence over time. This process is formalized with sequential sampling models, where evidence is accumulated up to a decision threshold before a choice is made. Although intuition suggests that decision formation must precede the preparation of a motor response (i.e., the action used to communicate the choice), neurophysiological findings have suggested that these two processes might be one and the same. To test this idea, we developed a reverse-correlation protocol in which the visual stimuli that influence decisions can be distinguished from those guiding motor responses. In three experiments, we found that the temporal weighting function of oculomotor responses did not overlap with the relatively early weighting function of stimulus properties having an impact on decision formation. These results support a timeline in which perceptual decisions are formed, at least in part, prior to the preparation of a motor response.

Highlights

Perceptual decisions often require the integration of noisy sensory evidence over time
Support for the intentional framework comes from neurophysiological investigations of the lateral intraparietal area (LIP), which seems to implement both sensorimotor transformation for eye movements as well as accumulation of sensory evidence in tasks that require oculomotor responses[5,8]
The results suggested that perceptual decisions and oculomotor responses were supported by distinct accruals of information, it is possible that the specific characteristics of the paradigm used in Experiment 1 encouraged a serial strategy that resulted in non-overlapping weighting functions

Summary

Introduction

Perceptual decisions often require the integration of noisy sensory evidence over time. The finding of neural correlates of evidence accumulation in motor and pre-motor areas has led to the influential intentional framework[7], according to which, ‘perceptual decision-making is implemented in the brain as a process of choosing between available motor actions rather than as a process of representing the properties of the sensory stimulus’[8] This implies that during decision-making there would be a continuous flow of information from sensory to motor areas, producing graded levels of readiness to execute motor responses that are proportional to the time integral of the sensory evidence. By showing that the precise parameters of the eye movement were determined by information sampled after the decision, our results demonstrate that the motor response was not yet ready to launch when the decision process terminated This suggests that perceptual decisions and speeded, oculomotor responses rely on temporally distinct streams of evidence

Methods

Results

Conclusion