M137. HIGH CONFIDENCE FOR VISUOMOTOR ACTION RECRUITS THE VENTRAL STRIATUM – A METACOGNITIVE APPROACH FOR UNDERSTANDING NEGATIVE SYMPTOMS?

BACKGROUND: Metacognition refers to the ability to discriminate between one’s own correct and incorrect decisions, thus representing a key function for goal-oriented behavior. The neurobiological underpinnings of metacognition have mainly been studied in perceptual decision-making and memory-related processes; therefore, mechanisms and neural correlates underlying metacognitive processes during visuomotor actions are still poorly characterized and the specific role of confidence remains to be elucidated. This is of particular interest as deficits in goal-directed behavior and insight both are a hallmark of the negative symptoms of schizophrenia. METHODS: We examined 31 healthy controls who were asked to draw straight reaching trajectories towards a visual target, while measuring their brain activity with functional Magnetic Resonance Imaging (fMRI). Deviations were introduced in 70% of the trajectories seen on the screen. Participants then reported awareness of deviations (first-order), followed by (second-order) confidence in their response. The amount of deviation was titrated to reach a 71% average detection rate using an adaptive staircase procedure. Metacognition was measured using the M-Ratio, which estimates the ratio of first-order information available for confidence computation (Maniscalco & Lau, 2012). Whole brain activity was analyzed via a parametric general linear model (GLM). RESULTS: Participants showed good metacognitive abilities at evaluating the correctness of their first-order responses (M-Ratio: 0.98±0.25). Movements were decomposed into two phases based on peaks in the variance of the trajectory deviation and actual joystick position. We found that confidence ratings after deviated trials were explained by a combination of the trajectory deviation in the initial phase (p=0.006; linear mixed model) and the amount of motor correction in the final phase of the movement (p<0.001). At the neural level, as expected, conscious detection of deviation engages strongly the visual cortex, whereas higher visuomotor corrections engage primarily the primary motor cortex. Importantly, we show that high confidence specifically recruits the ventral striatum bilaterally (p<0.05 corrected for multiple comparisons), suggesting a role for confidence in motivating action. DISCUSSION: Taken together, these results show for the first time in healthy controls that confidence for visuomotor action strongly engages motivational regions in line with a key role of metacognition in goal directed behavior and accurate insight into self-performed actions. These results in healthy controls are currently being tested in a cohort of schizophrenia patients and our hypothesis is that patients with higher level of apathy will display lower metacognitive confidence and lower ventral striatum activity