EVALUATION OF INHIBITION RESPONSE BEHAVIOR USING THE GO/NO-GO PARADIGM IN NORMAL INDIVIDUALS: EFFECTS OF VARIATIONS IN THE TASK DESIGN

Background: Inhibitory control is an important executive function and a deficiency in action inhibition has been characterized as core in a number of neuropsychiatric disorders. The Go/No-Go (GNG) paradigm is a wellknown method to evaluate an inhibitory response. We developed seven versions of the GNG to evaluate the effect of different psychometric properties on GNG scores in normal healthy subjects. Material/Methods: Fifty seven healthy subjects including 38 (66.7%) males, aged 18 to 55 (mean +/- SD: 33.7 +/- 8.1) participated in this study. Each subject conducted seven variants of GNG tasks in a randomized order after being given instruction to respond to a selected stimulus displayed on a screen by pressing the space bar as quickly as possible (Go stimuli) and withholding responses to other stimuli (No-Go stimuli). To develop seven versions of varying difficulty, we manipulated the task context by making changes in stimulus complexity, stimulus presentation time, inter-stimulus intervals and the probability of target occurrence. Results: Decreasing the stimulus presentation time and simultaneously using more complex stimuli caused a significant decrease in true hits on Go trials, which is a good marker for response initiation, while an increase in the ratio of No-Go/Go trials led to a decrease in commission errors in No-Go trials, which is a good marker of response inhibition. Further analysis revealed that reaction time and age did not influence the GNG task scores while education level and gender may affect scores of Go trials but not No-Go trials. Conclusions: Manipulation in both stimulus complexity and presentation time caused significant changes in response initiation scores, while alteration in the ratio of No-Go/Go trials led to significant changes in motor inhibition scores. Optimization of GNG tasks to measure response inhibition and initiation could be achieved with psychometric manipulation on various features of stimulus presentation for different target populations.