Poster F127, Tuesday, March 27, 8:00-10:00 am, Exhibit Hall C
Neural Correlates of Encoding and Retrieving Probabilities of Event Occurrences.
I-Tzu Hung1,2, Joshua Oon Soo Goh2,3; 1National Health Research Institutes, Miaoli, Taiwan, 2National Taiwan University, Taipei, Taiwan, 3National Institute on Aging, Baltimore, MD, USA
Knowledge of the probability of events facilitates better decision-making behaviors. However, how the brain encodes and retrieves information about event frequencies remains unclear. In this functional magnetic resonance imaging experiment, 19 participants (mean age (SD): 22.53 (2.46) yrs; age range: 20-29 yrs; 9 females) viewed series of 1s and 0s with different probability levels (10%, 30%, 50%) of occurrence and then reported subjective perceptions of event probabilities. Judgments showed a significant main effect of probability (F = 6.544, p < 0.05), with rare events evoking an overestimation bias that decreased as event frequency increased towards chance levels (mean (SD) 10%: +5.44 (4.67); 30%: +2.92 (4.36); 50%: +0.48 (7.18)). Judgment variability was highest at chance. Encoding brain responses were higher for 10% than 30% conditions in right middle and anterior medial frontal, bilateral parietal, and precuneus regions, and higher for 50% than 30% conditions in right middle frontal and bilateral inferior occipito-temporal regions. Neural responses were higher for 50% than 10% conditions. Thus, encoding of rare and chance events engaged distinct brain processes and the intermediate case recruited lowest neural activity. For retrieval, brain responses were higher for 10% than both 30% and 50% conditions in bilateral parieto-occipital, lingual, and right orbitofrontal regions. Such difference in retrieval activity across probability might stem from differential encoding of rare to chance event frequencies, with rare events involving more heuristic biases. Our findings have implications for theories on neural representation of probability and uncertainty for decisions.
Topic Area: THINKING: Decision making