Activity in the right frontal cortex is dependent on inhibitory-demand: a functional near infrared spectroscopy study

The ability to supress inappropriate or unwanted behaviour, known as inhibition, can be indexed using a variety of task paradigms, one of the more common being the Go/No-go task. Studies in which popular neuroimaging methods such as functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) were used to measure neural activity during participant performance of the Go/No-go task have often identified ‘inhibitory-related’ activity in the right prefrontal cortex (PFC). While studies using functional near-infrared spectroscopy (fNIRS) have also identified changes in activity in the right PFC, the variants of the Go/No-go tasks previously employed in those studies have made it difficult to be confident that those changes measured using fNIRS were specifically related to inhibition. To determine whether the change in activity identified in the right PFC with fNIRS by previous studies using the Go/No-go task were indeed related to inhibition, we had participants complete three conditions of the Go/No-go task, each with varying levels of inhibitory demand (manipulated by the relative frequency of Go to No-go trials). We found that as Go-trial frequency increased, participants performed faster on Go-trials and less accurately on No-go trials. More importantly, as inhibitory-demand increased, activity in the right but not left PFC increased. When taken together, these findings are in support of the idea that the changes measured in the right PFC in earlier studies using fNIRS during the Go/No-go task were indeed related to inhibition.