Right hemispheric dominance of inhibitory control: an event-related functional MRI study - PubMed (original) (raw)

H Garavan et al. Proc Natl Acad Sci U S A. 1999.

Abstract

Normal human behavior and cognition are reliant on a person's ability to inhibit inappropriate thoughts, impulses, and actions. The temporal and spatial advantages of event-related functional MRI (fMRI) were exploited to identify cortical regions that showed a transient change in fMRI signal after the withholding of a prepotent motor response. The temporal specificity of the event-related fMRI design also minimized possible contamination from response inhibition errors (i. e., commission errors) and other extraneous processes. Regions identified were strongly lateralized to the right hemisphere and included the middle and inferior frontal gyri, frontal limbic area, anterior insula, and inferior parietal lobe. Contrary to the prominence traditionally given to ventral frontal regions for response inhibition, the results suggest that response inhibition is accomplished by a distributed cortical network.

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Figures

Figure 1

Figure 1

Response-inhibition task. This schematic representation of the task indicates that subjects responded, with alternation, to the target letters X and Y, and withheld response on nonalternating presentations of these target letters. Letters were presented for 500 msec in black against a white background with 0-msec interstimulus interval.

Figure 2

Figure 2

ER–fMRI time-series analysis. Example of an average fMRI time series, time-locked to correct response inhibitions, taken from a voxel in the dorsolateral prefrontal cortex of one subject. The averaged data are represented by ■ and the best-fitting γ-variate function is represented by the smooth line. The portion of the curve before departure from baseline was fitted with a flat line. Departure points were constrained to occur within 4 sec of the lure presentation. The scaling parameter, k, was free to vary, whereas the exponential parameters were constrained as follows: 8 ≤ r ≤ 9, 0.15 ≤ b ≤ 0.45. To provide a measure of the response magnitude, the area under the curve was expressed as a percentage of the area under the baseline, determined by the linear portion of the fitted model and its continuation (shown as a dashed line).

Figure 3

Figure 3

Response inhibition activation. Significant right hemisphere activation during response inhibition is shown on one subject’s anatomy. Areas shown include the inferior frontal gyrus (1), middle frontal gyrus (2), insula (3), and inferior parietal lobule (4). The axial slice is 41 mm anterior to the anterior commissure, and the anatomy has been made slightly transparent to reveal the activation that lies just below the cortical surface.

Figure 4

Figure 4

Correlation between mean response time (msec) to targets and the mean activation within the right inferior frontal cluster (Upper) and the left inferior parietal lobule cluster (Lower).

Figure 5

Figure 5

Functional activation associated with response inhibition for lures (red) and response executions for targets (green) are displayed on one subject’s anatomy. Responding to target letters produced activation in striatal (1), primary motor, premotor, SMA proper (2), and bilateral parietal regions (3). Also shown in red is the pre-SMA activation observed during response inhibition. The coronal slice is 16 mm anterior and the axial slice is 46 mm superior to the anterior commissure.

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