Inhibitory Control is Slowed in Patients with Right Superior Medial Frontal Damage

Abstract

Inhibitory control is an essential part of behavior. Comprehensive knowledge of the neural underpinnings will shed light on complex behavior, its breakdown in neurological and psychological disorders, and current and future techniques for the pharmacological or structural remediation of disinhibition. This study investigated the neural mechanisms involved in rapid response inhibition. The stop signal task was used to estimate inhibitory speed in a group of neurologically normal control subjects and patients with discrete frontal lobe lesions. Task procedures were controlled to rule out probable confounds related to strategic changes in task effort. The findings indicate that the frontal lobes are necessary for inhibitory control and, furthermore, that the integrity of the right superior medial frontal region is key for rapid inhibitory control under conditions controlling for strategically slow responses, forcing reliance more on a rapid, "kill-switch" inhibitory system. These results are interpreted within an anatomical framework of corticospinal motor control.

Distinct frontal systems for response inhibition, attentional capture, and error processing

“…Our results are consistent with previous studies demonstrating that the medial PFC is necessary for motor inhibition (4,9,16,17). In monkeys, microstimulation of the supplementary eye field within the medial prefrontal cortex improved performance on an oculomotor version of the SST by delaying saccade inhibition (9), and stimulation of the pre-SMA inhibited automatic unwanted actions while facilitating a desired alternative (10).…”

“…Previous work with this task provides evidence that both medial frontal regions, including the presupplementary motor area (pre-SMA), and more lateral regions, including the right inferior frontal gyrus (IFG; rIFG) and insula (Ins), are involved in stopping. However, the specific contributions of these regions to motor control are unresolved (2)(3)(4). Many functional imaging studies have demonstrated activation of right inferior frontal regions during stopping (2,(5)(6)(7)(8) and individual differences in response inhibition correlate with the magnitude of the IFG/Ins activation during the SST (5).…”

“…Pre-SMA activation is correlated with the efficiency of inhibitory processing (2), and work in nonhuman primates supports a role for the medial prefrontal regions in behavioral inhibition (9,10). Neuropsychological studies provide discrepant results, with correlations between the extent of damage and impairments of inhibitory function reported for both the right lateral and medial frontal regions (3,4).…”

Converging Evidence for a Fronto-Basal-Ganglia Network for Inhibitory Control of Action and Cognition: Figure 1.

“…Furthermore, experimentally induced microstimulation of preSMA neurons led to a greater proportion of switch trials being successful. Combined with the findings in humans that preSMA lesions affect stopping (Floden and Stuss, 2006;Nachev et al, 2007) and that the preSMA is directly connected with the IFC and the STN region , these findings strongly implicate the dorsomedial frontal cortex in control over motor responses. Future research will need to precisely determine how the nodes in this network interact.…”

“…Two recent studies identified a third critical node for the stopping process in the dorsomedial frontal cortex, including the presupplementary motor area (preSMA) (Floden and Stuss, 2006;Nachev et al, 2007). Interestingly, the preSMA was also found to be directly connected with both the right IFC and the right STN region via white matter tracts (Fig.…”