One bad apple spoils the whole bushel: The neural basis of outlier processing Abstract   How are outliers in an otherwise homogeneous object ensemble represented by our visual system? Are outliers ignored because they are the minority? Or do outliers alter our perception of an otherwise homogeneous ensemble? We have previously demonstrated ensemble representation in human anteriormedial ventral visual cortex (overlapping the sceneselective parahippocampal place area; PPA). In this study we investigated how outliers impact objectensemble representation in this human brain region as well as visual representation throughout posterior brain regions. We presented a homogeneous ensemble followed by an ensemble containing either identical elements or a majority of identical elements with a few outliers. Human participants ignored the outliers and made a samedifferent judgment between the two ensembles. In PPA, fMRI adaptation was observed when the outliers in the second ensemble matched the items in the first, even though the majority of the elements in the second ensemble were distinct from those in the first; conversely, release from fMRI adaptation was observed when the outliers in the second ensemble were distinct from the items in the first, even though the majority of the elements in the second ensemble were identical to those in the first. A similarly robust outlier effect was also found in other brain regions, including a shapeprocessing region in lateral occipital cortex (LO) and taskprocessing frontoparietal regions. These brain regions likely work in concert to flag the presence of outliers during visual perception and then weigh the outliers appropriately in subsequent behavioral decisions. To our knowledge, this is the first time the neural mechanisms involved in outlier processing have been systematically documented in the human brain. Such an outlier effect could well provide the neural basis mediating our perceptual experience in situations like xe2x80x9cone bad apple spoils the whole bushelxe2x80x9d.

Anterior insula reflects surprise in valuebased decisionmaking and perception Abstract   The brain has been theorized to employ inferential processes to overcome the problem of uncertainty. Inference is thought to underlie neural processes, including in disparate domains such as valuebased decisionmaking and perception. Valuebased decisionmaking commonly involves deliberation, a timeconsuming process that requires conscious consideration of decision variables. Perception, by contrast, is thought to be automatic and effortless. Both processes may call on a general neural system to resolve for uncertainty however. We addressed this question by directly comparing uncertainty signals in visual perception and an economic task using fMRI. We presented the same individuals with different versions of a bistable figure (Neckeru0027s cube) and with a gambling task during fMRI acquisition. We experimentally varied uncertainty, either on perceptual state or financial outcome. We found that inferential errors indexed by a formal account of surprise in the gambling task yielded BOLD responses in the anterior insula, in line with earlier findings. Moreover, we found perceptual uncertainty and surprise in the Necker Cube task yielded similar responses in the anterior insula. These results suggest that uncertainty, irrespective of domain, correlates to a common brain region, the anterior insula. These findings provide empirical evidence that the brain interacts with its environment through inferential processes.