Action control and selection in social disinhibition following severe TBI: a pavlovian-to-instrumental transfer and outcome devaluation study.

Introduction: Social disinhibition is a significant sequela of severe traumatic brain injury (TBI). Some research suggests that it could reflect a deficiency in goal-directed behavior. The current study aimed to test whether these inappropriate behaviors tend to be deficient in goal-directed control, that is, triggered more by environmental stimuli than by the known consequences of their actions.

Method: We used a between-group design with 25 adult participants with severe TBI, and 27 control participants. Social disinhibition was measured using Frontal Systems Behavior Scale and Social Disinhibition Interview. Changes in reward-related goal-directed behavior were evaluated using a computer-based task in which we assessed the influence of cues predicting reward and of reward devaluation on choice performance.

Results: We found no difference in the levels of social disinhibition between the TBI and control groups and, using mixed two-way ANCOVAs, no overall effect of the stimuli or outcome devaluation. However, after combing these groups and splitting them based on their disinhibition levels, a significant interaction between group (High vs Low disinhibition) and reward type (Valued vs Devalued) in sensitivity to outcome devaluation test (F = 5.99, p = .01, ηp2 = .13) appeared. Comparing with the baseline rate of responding, the Low disinhibition group decreased their responding to devalued and increased their responding to still-valued outcomes. In contrast, the High disinhibition group showed the opposite pattern of choice performance.

Conclusions: It appears that people with clinical levels of social disinhibition are both prone to outcome-response priming effects and insensitive to changes in the value of the consequences of their actions, that is, despite evidence they were aware of the reduction in the value of their actions's outcomes, people with high-level disinhibition kept performing those actions. This pattern has the hallmarks of a habit suggesting their disinhibition reflects a loss of executive control.