Determining Monkey Free Choice Long before the Choice Is Made: The Principal Role of Prefrontal Neurons Involved in Both Decision and Motor Processes.

Encarni Marcos,Aldo Genovesio

doi:10.3389/fncir.2016.00075

Abstract

When choices are made freely, they might emerge from pre-existing neural activity. However, whether neurons in the prefrontal cortex (PF) show this anticipatory effect and, if so, in which part of the process they are involved is still debated. To answer this question, we studied PF activity in monkeys while they performed a strategy task. In this task when the stimulus changed from the previous trial, the monkeys had to shift their response to one of two spatial goals, excluding the one that had been previously selected. Under this free-choice condition, the prestimulus activity of the same neurons that are involved in decision and motor processes predicted future choices. These neurons developed the same goal preferences during the prestimulus presentation as they did later in the decision phase. In contrast, the same effect was not observed in motor-only neurons and it was present but weaker in decision-only neurons. Overall, our results suggest that the PF neuronal activity predicts upcoming actions mainly through the decision-making network that integrate in time decision and motor task aspects.

Highlights

Decision-making has been traditionally studied using experimental paradigms in which the correct choice is determined by a set of instructions
To determine whether neurons modulated their activity before the stimulus was presented, we focused our analyses on the change-shift trials and on three kinds of neurons: those that were involved in the decision process but not in motor selection, those that were involved during motor selection but not during decision making and those that were involved in both decision making and motor selection
We identified 143 of 887 (16%) neurons modulated by goal location during the prestimulus period and 145 neurons (16%) modulated during the reaction and movement time (RMT) period with 42 neurons belonging to the two groups (Figure 2A)

Summary

Introduction

Decision-making has been traditionally studied using experimental paradigms in which the correct choice is determined by a set of instructions. Little attention has been paid to how decisions are made when subjects are free to decide when to act or which choice to make In the latter situation of free choice, most experiments have focused on cases in which the options that are provided are neither correct nor incorrect but have different associated values (Thorndike, 1898; Herrnstein, 1961). Under such conditions, decisions are the result of a noisy, deliberative process in which the value of each option is compared and assessed (Gold and Shadlen, 2007). During perceptual judgment tasks with ambiguous or nearly ambiguous stimuli, certain neurons in the lateral intraparietal cortex (LIP), medial superior temporal area (MST) and

Methods

Results

Conclusion