Neural bases of individual variation in decision time
Abstract
People make decisions by evaluating existing evidence against a threshold or level of confidence.
Individuals vary widely in response times even when they perform a simple task in the laboratory.
We examine the neural bases of this individual variation by combining computational modeling and brain imaging of 64 healthy adults performing a stop signal task.
Behavioral performance was modeled by an accumulator model that describes the process of information growth to reach a threshold to respond. In this model, go trial reaction time (goRT) is jointly determined by the information growth rate, threshold, and movement time (MT).
In a linear regression of activations in successful go and all stop (Go+Stop) trials against goRT across participants, the insula, supplementary motor area (SMA), pre‐SMA, thalamus including the subthalamic nucleus (STN), and caudate head respond to increasing goRT. Among these areas, the insula, SMA, and thalamus including the STN respond to a slower growth rate, the caudate head responds to an elevated threshold, and the pre‐SMA responds to a longer MT.
In the regression of Go+Stop trials against the stop signal reaction time (SSRT), the pre‐SMA shows a negative correlation with SSRT. These results characterize the component processes of decision making and elucidate the neural bases of a critical aspect of inter‐subject variation in human behavior.
These findings also suggest that the pre‐SMA may play a broader role in response selection and cognitive control rather than simply response inhibition in the stop signal task. Hum Brain Mapp 35:2531–2542, 2014. © 2013 Wiley Periodicals, Inc.
