Assessing inhibitory control: A revised approach to the stop signal task

Abstract

The stop signal task (stop task) is designed to assess inhibitory control and is a frequently used research tool in clinical disorders such as ADHD and schizophrenia. Previous methods of setting stop signal delay and of assessing inhibitory control are problematic. The current study reports two modifications that improve the task as a measure of inhibitory control. The first modification was to set stop signal delays proportional to go mean reaction time (go MRT) to better account for inter-subject variability in go MRT. Twenty-eight normal children were tested, and all standard, stop task dependent measures were obtained when delays were set by this method. The second modification was to calculate a novel dependent measure called the area of inhibition (AOI) which provides a more complete measure of inhibitory control than the slope of the relative finishing time z-scores (ZRFT-slope). Implications for the assessment of inhibitory control in clinical populations are discussed.

Brief Report: Executive Functioning in Autism Spectrum Disorders: A Gender Comparison of Response Inhibition

“…Standard measures of response inhibition were extracted (see Logan 1994, andCarter et al 2003 for a detailed explanation). This included stop signal reaction time (SSRT) (ms), which provides an estimate of the speed of stopping, z-scores of the relative finishing times gradient (ZRFT-gradient), which provides a measure of the ability to trigger stopping processes, and area of inhibition (AoI), which provides an estimate of the amount a participant is able to inhibit.…”

“…As described within Logan's (1994) ''race model,'' in which inhibition is determined by a ''race'' between go and stop processes, an increased SSD is typically associated with a reduced likelihood of successful stopping. Four SSD intervals were used: 20, 40, 60, and 80% of mean response time (MRT; Carter et al 2003). MRT was determined immediately prior to the stop task by administering 20 go signal trials (10 on each side, presented at random).…”

A Novel Translational Assay of Response Inhibition and Impulsivity: Effects of Prefrontal Cortex Lesions, Drugs Used in ADHD, and Serotonin 2C Receptor Antagonism

“…A main task manipulation was to assess the effects of making stopping more or less difficult by having interpolated stop trials where the auditory stop-signal was presented further away or closer to the execution of the response. At baseline, in stop trials the stop-signal was always presented coincident with the beginning of the response (making stopping relatively easy) but in separate probe sessions the position of the stop-signal was presented at different positions relative to the individual correct go reaction times of each mouse, ie at 0, 10, 50 and 90% into the individualized go reaction time, where 90% is close to the execution of the response and stopping therefore more difficult, as described in Carter et al (2003). Individualized reaction times were required to normalize the relative position of the stop-signal across individuals, this was important as animals can have differing go reaction times.…”

Stop task after-effects in schizophrenia: Behavioral control adjustments and repetition priming

“…Four stop signal delay (SSD; time between presentation of go signal and presentation of the stop signal) intervals were used: 20, 40, 60, and 80% of each individual participant's mean response time (Carter et al, 2003). SSD began with the extinction of the fixation LED.…”