The role of prefrontal cortex sub-circuits in impulse control and preference consistency: Behavioural analyses in patients with focal prefrontal cortex lesions.
Final Report Abstract
The current project examined the role of orbitofrontal cortex (OFC) regions in decision-making and impulse control. A group of patients with focal lesions to medial OFC and age- and education-matched controls performed a range of decision-making tasks. Preliminary data suggest that OFC damage increases impulsivity, and that this effect is unlikely to be related to increases in within-session choice stochasticity. Choice stochasticity was also not impaired in a simple preference judgement task, in contrast to previous findings. A simple attractiveness rating task for different monetary rewards revealed that patients showed significantly decreased sensitivity to reward magnitudes, suggesting that their impairment may extend to situations that do not explicitly involve making choices. Finally, reward-based learning was impaired in OFC patients, and preliminary analyses suggest that this impairment may have affected both model-based and model-free learning. Although preliminary, our results highlight the importance of medial OFC for a range of reward-dependent behaviours, and suggest that impulsivity following OFC damage is unlikely to be confounded by increases in choice stochasticity. For scientific reasons, two additional tasks where included in the testing battery. Associated additional programming and computational modelling work delayed the start of data acquisition. For this reason, recruitment of additional elderly control subjects is ongoing. Scheduling and recruiting patients was also more difficult than anticipated. Patients where much more involved in other ongoing projects than anticipated, and only a single DLPFC patient could be tested during the time at UC Berkeley. The OFC patients where more readily available, but due to additional study commitments at the time of writing no OFC patient had been invited for a re-testing session to assess preference stability. However, the re-testing of these patients, as well as testing of additional agematched controls, is scheduled for early 2015 at the UC Berkeley location.
