Deficiencies in inhibitory mechanism in obesity

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University of Delaware
Theories of human obesity often refer to deficiencies in inhibitory control. An important component of inhibitory control is the ability to make on-the-fly adjustments like those required when interference is encountered or when a prepotent response needs to be interrupted (Barch et al., 2009). The inhibition of an ongoing response is frequently studied using the stop signal reaction time (SSRT) task. An SSRT task is normally a choice reaction time task with embedded trials in which a ‘Stop’ signal appears and requires that the subject completely inhibit a response initiated to one of the ‘Go’ signals. The time required to stop is computed and ERPs associated with the stop signal can be recorded (deJong et al., 2000). While many studies point to a general inhibitory deficit in obesity, the question remains whether food stimuli are linked to even greater deficits in obese individuals. By varying the content of the ‘Go’ signal, it may be possible to determine whether inhibitory control deficits associated with obesity are greater to food cues. The present experiment was designed to address this issue. ERPs were recorded while fifty-six obese and normal weight undergraduates performed an SSRT task in which ‘Go’ signals were either neutral pictures or highly appetitive positive pictures including high calorie, high fat foods. No behavioral differences were found between the two groups. In control subjects, successful stop trials were associated with larger P300s than were the unsuccessful stop trials, though this P300 difference was absent in the obese subjects. In the obese group, no differences were found among the stimuli, suggesting that the inhibitory control deficit is general and that food is not linked with greater inhibitory difficulties.