Figure 1.
Experimental design of the Simon Spatial Incompatibility Task.
Table 1.
Participants Characteristics.
Figure 2.
Behavioral results. Mean reaction times (± standard errors) of stutterers and healthy controls for current trial congruency were plotted under modulation of preceding trial congruency.
Abbreviations: cC = congruent trials immediately preceded by a congruent trial; cI = incongruent trials immediately preceded by a congruent trial; iC = congruent trials immediately preceded by an incongruent trial; iI = incongruent trials immediately preceded by an incongruent trial.
Figure 3.
(A) Representative axial–oblique slices depict greater activation of stutterers relative to healthy controls in frontostriatal regions when resolving Simon conflict (activation contrast: incongruent trials immediately preceded by a congruent trial versus congruent trials immediately preceded by a congruent trial). Abbreviations: ACC = anterior cingulate cortex; Cau = caudate; IPC = inferior parietal cortex; SMA = supplementary motor area. (B) Axial–oblique views of attenuated activation in the dorsolateral prefrontal cortex of stutterers as compared to healthy controls during response to incongruent trials under the influence of congruency of preceding trial (context-dependent adaptation, activation contrast: incongruent trials immediately preceded by an incongruent trial versus incongruent trials immediately preceded by a congruent trial). Abbreviations: DLPFC = dorsolateral prefrontal cortex. Statistical maps were displayed at a threshold of p<0.025 with a cluster extent of 30 voxels (P<0.05, corrected). The left-hand sides of the images correspond to the left side of the brain. The color bars indicate the t-values. The coordinates in Montreal Neurological Institute space are defined in millimeters.
Table 2.
Brain Regions of Group-Level Differences during Performance of the Simon Task.
Figure 4.
Axial–oblique views of brain regions in stutterers show negative correlations between the magnitude of brain activation during conflict resolution and stuttering severity as measured with the ACES and OASES. The scatter plot illustrates the negative association in the ACC between the standardized severity score and the parameter estimate of brain responses during conflict resolution (r = −0.33, p<0.025). Abbreviations: ACC = anterior cingulate cortex.
Table 3.
Regions of Significant Correlation between fMRI Activation during Conflict Resolution and Severity of Stutteringa.
Table 4.
Granger Causality Analyses for the Anterior Cingulate Cortex and Dorsolateral Prefrontal Cortex during Performance of the Simon Task.