Considerable debate persists around the definition of risk. Depending on the area of study, the concept of risk may be defined as the variance of the possible outcomes, the probability of a loss, or a combination of the loss probability and its maximum possible loss. Mounting evidence suggests the anterior cingulate cortex (ACC), including the surrounding medial prefrontal cortex (mPFC), and the anterior insula/inferior frontal gyrus (IFG) are key neural regions that represent perceived risks. Yet it remains unclear which of these formalisms best accounts for the pattern of activation in brain regions representing risk, and it is also difficult to disentangle risk from value, as both contribute to perceived utility. To adjudicate among the possible definitions, we used fMRI with a novel gambling task that orthogonalized the variance, loss probability, and maximum possible loss among the risky options, while maintaining a constant expected value across all monetary gambles to isolate the impact of risk rather than value. Here we show that when expected value is controlled for ACC and IFG activation reflect variance, but neither loss probability nor maximum possible loss. Across subjects, variance-related activation within the ACC correlates indirectly with risk aversion. Our results highlight the variance of the prospective outcomes as a formal representation of risk that is reflected both in brain activity and behavior, thus suggestive of a stronger link among formal economic theories of financial risk, naturalistic risk taking, and neural representations of risk.
Prominent conceptual models characterize schizophrenia as a dysconnectivity syndrome, with recent research focusing on the contributions of the cerebellum in this framework. The present study examined the role of the cerebellum and its effective connectivity to the cerebrum during sensorimotor synchronization in schizophrenia. Specifically, the role of the cerebellum in temporally coordinating cerebral motor activity was examined through path analysis. Thirty-one individuals diagnosed with schizophrenia and 40 healthy controls completed a finger-tapping fMRI task including tone-paced synchronization and self-paced continuation tapping at a 500 ms intertap interval (ITI). Behavioral data revealed shorter and more variable ITIs during self-paced continuation, greater clock (vs motor) variance, and greater force of tapping in the schizophrenia group. In a whole-brain analysis, groups showed robust activation of the cerebellum during self-paced continuation but not during tone-paced synchronization. However, effective connectivity analysis revealed decreased connectivity in individuals with schizophrenia between the cerebellum and primary motor cortex but increased connectivity between cerebellum and thalamus during self-paced continuation compared with healthy controls. These findings in schizophrenia indicate diminished temporal coordination of cerebral motor activity by cerebellum during the continuation tapping portion of sensorimotor synchronization. Taken together with the behavioral finding of greater temporal variability in schizophrenia, these effective connectivity results are consistent with structural and temporal models of dysconnectivity in the disorder.
Humans may retrieve words from memory by exploring and exploiting in linguistic "space" similar to hownon-human animals forage for resources in physical space. This has been studied using the verbalfluency test (VFT), in which participants generate words belonging to a semantic or phonetic category in alimited time. The foraging in mind model proposes that individuals performing VFT monitor their responseproduction rate as they search through and deplete a local patch (subcategory) of items in memory andthen switch to a new patch in another part of semantic or phonetic space. An alternative model holds thatparticipants use a random walk process, and switches are merely epiphenomenal long steps reflectingthe tail of the random walk step size distribution. This study tests these competing theories by examiningwhether there is distinct neural activity during exploring between ("switching") versus exploiting within("clustering") related response groupings (foraging), or no neural differences between search phases(random walk). Thirty participants performed category and letter VFT during functional magneticresonance imaging. Responses were categorized as cluster or switch events based on computationalmetrics of similarity and participant evaluations. Findings provide neural evidence of a cognitive foragingprocess, with greater hippocampal and cerebellar activation during switching compared to clustering,even while controlling for greater semantic and phonetic distance and response times. Furthermore,these regions exhibited ramping activity leading up to switch events. These results clarify how neuralswitch processes may guide memory searches in a manner akin to foraging in patchy spatialenvironments.
BackgroundBipolar disorder is associated with heightened and persistent positive emotion (Gruber in Curr Dir Psychol Sci 20:217–221, 2011; Johnson in Clin Psychol Rev 25:241–262, 2005). Yet little is known about information processing biases that may influence these patterns of emotion responding.MethodsThe current study adopted eye-tracking methodology as a continuous measure of sustained overt attention to monitor gaze preferences during passive viewing of positive, negative, and neutral standardized photo stimuli among remitted bipolar adults and healthy controls. Percentage fixation durations were recorded for predetermined areas of interest across the entire image presentation, and exploratory analyses were conducted to examine early versus late temporal phases of image processing.ResultsResults suggest that the bipolar and healthy control groups did not differ in patterns of attention bias.ConclusionsFindings provide insight into apparently intact attention processing despite disrupted emotional responding in bipolar disorder.
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