Inhibitory behavioral control: a stochastic dynamic causal modeling study using network discovery analysis

Abstract

This study employed functional magnetic resonance imaging (fMRI)-based dynamic causal modeling (DCM) to study the effective (directional) neuronal connectivity underlying inhibitory behavioral control. fMRI data were acquired from 15 healthy subjects while they performed a Go/NoGo task with two levels of NoGo difficulty (Easy and Hard NoGo conditions) in distinguishing spatial patterns of lines. Based on the previous inhibitory control literature and the present fMRI activation results, 10 brain regions were postulated as nodes in the effective connectivity model. Due to the large number of potential interconnections among these nodes, the number of models for final analysis was reduced to a manageable level for the whole group by conducting DCM Network Discovery, which is a recently developed option within the Statistical Parametric Mapping software package. Given the optimum network model, the DCM Network Discovery analysis found that the locations of the driving input into the model from all the experimental stimuli in the Go/NoGo task were the amygdala and the hippocampus. The strengths of several cortico-subcortical connections were modulated (influenced) by the two NoGo conditions. Specifically, connectivity from the middle frontal gyrus (MFG) to hippocampus was enhanced by the Easy condition and further enhanced by the Hard NoGo condition, possibly suggesting that compared with the Easy NoGo condition, stronger control from MFG was needed for the hippocampus to discriminate/learn the spatial pattern in order to respond correctly (inhibit), during the Hard NoGo condition.

Keywords: Go/NoGo; dynamic causal modeling; impulsivity; inhibitory control; top-down.

FIG. 1.

Examples of the stimuli used in the Go/NoGo response inhibition task. (A) Go stimulus; (B) Easy NoGo stimulus; and (C) Hard NoGo stimulus.

FIG. 2.

Schematic diagram representing effective connectivity only modulated by the NoGo conditions. The endogenous connections are denoted by lines with arrows. The modulation effects are depicted by lines ending with a black dot. The legend in the bottom-left corner provides rough information about the relationship between line thickness (or line type) and effective connectivity strength. The mean strengths (in units of Hz) of the modulation effects exerted by the Easy (E) or Hard (H) NoGo condition are shown separately. For clarity, not all nodes and endogenous connections are shown in this figure. Only the connections that were modulated by NoGo conditions (but not Go conditions) and only the brain regions related to these connections are included. L, left. R, right.