Sleep deprivation elevates expectation of gains and attenuates response to losses following risky decisions.

STUDY OBJECTIVES: Using a gambling task, we investigated how 24 hours of sleep deprivation modulates the neural response to the making of risky decisions with potentially loss-bearing outcomes. DESIGN: Two experiments involving sleep-deprived subjects were performed. In the first, neural responses to decision making and reward outcome were evaluated. A second control experiment evaluated responses to reward outcome only. PARTICIPANTS: Healthy right-handed adults participated in these experiments (26 [mean age 21.3 years] in Experiment 1 and 13 [mean age 21.7 years] in Experiment 2.) MEASUREMENTS AND RESULTS: Following sleep deprivation, choices involving higher relative risk elicited greater activation in the right nucleus accumbens, signifying an elevated expectation of the higher reward once the riskier choice was made. Concurrently, activation for losses in the insular and orbitofrontal cortices was reduced, denoting a diminished response to losses. This latter finding of reduced insular activation to losses was also true when volunteers were merely shown the results of the computer's decision, that is, without having to make their own choice. CONCLUSIONS: These results suggest that sleep deprivation poses a dual threat to competent decision making by modulating activation in nucleus accumbens and insula, brain regions associated with risky decision making and emotional processing.

Functional neuroimaging and behavioral correlates of capacity decline in visual short-term memory after sleep deprivation.

Sleep deprivation (SD) impairs short-term memory, but it is unclear whether this is because of reduced storage capacity or processes contributing to appropriate information encoding. We evaluated 30 individuals twice, once after a night of normal sleep and again after 24 h of SD. In each session, we evaluated visual memory capacity by presenting arrays of one to eight colored squares. Additionally, we measured cortical responses to varying visual array sizes without engaging memory. The magnitude of intraparietal sulcus activation and memory capacity after normal sleep were highly correlated. SD elicited a pattern of activation in both tasks, indicating that deficits in visual processing and visual attention accompany and could account for loss of short-term memory capacity. Additionally, a comparison between better and poorer performers showed that preservation of precuneus and temporoparietal junction deactivation with increasing memory load corresponds to less performance decline when one is sleep-deprived.

A conceptual history of Koro.

Koro is a culture-bound syndrome characterized by a fear that the genitals or breasts will retract into the body and cause death. Here we consider the history of ideas about Koro, from early concepts in traditional Chinese medicine (TCM) to contemporary ideas from medicine and sociology. This conceptual history reveals important issues about the classification (nosology) of Koro. In doing so, it demonstrates the need to integrate standardized phenomenological criteria with etiological models in order to capture the important features of complex behavioral disorders in the cross-cultural setting.

The neural basis of interindividual variability in inhibitory efficiency after sleep deprivation.

Sleep deprivation results in the loss of our ability to suppress a prepotent response. The extent of decline in this executive function varies across individuals. Here, we used functional magnetic resonance imaging to study the neural correlates of sleep deprivation-induced differences in inhibitory efficiency. Participants performed a go/no-go task after normal sleep and after 24 h of total sleep deprivation. Regardless of the extent of change in inhibitory efficiency, sleep deprivation lowered go/no-go sustained, task-related activation of the ventral and anterior prefrontal (PFC) regions bilaterally. However, individuals better able to maintain inhibitory efficiency after sleep deprivation could be distinguished by lower stop-related, phasic activation of the right ventral PFC during rested wakefulness. These persons also showed a larger rise in such activation both here and in the right insula after sleep deprivation relative to those whose inhibitory efficiency declined.

The long-term effects of mild head injury on short-term memory for visual form, spatial location, and their conjunction in well-functioning university students.

Research has suggested the presence of subtle long-term cognitive changes in otherwise well-functioning individuals who have previously sustained a mild head injury (MHI). This paper investigated the long-term effects of MHI on visual, spatial, and visual-spatial short-term memory in well-functioning university students. Sixteen students who reported having sustained a MHI were compared to 16 controls on tests of short-term memory (STM) for abstract polygons in haphazardly arranged locations. The three tests differed only in the requirements for recall (shapes for the visual task, locations for the spatial task, and the shapes in their respective locations for the visual-spatial task). MHI participants were selectively impaired on spatial memory, suggesting that tasks of spatial STM may be more sensitive, compared to tasks of visual STM, to the subtle long-term cognitive changes that may be present after a MHI.

Verbal and spatial short-term memory: common sources of developmental change?

Verbal and spatial span, articulation and tapping rate, and verbal and spatial speed-of-search tasks were administered to sixty 6- to 12-year-olds. A variance-partitioning procedure was then used to identify age-related and age-invariant components of variance in span. Outcomes were very similar for verbal and spatial span, in particular, (i) most of the age-related variance was shared by the speed-of-search and rate predictors, (ii) articulation rate provided an age-independent contribution, (iii) changing-state versions of predictor tasks did not account for variance over steady-state versions, and (iv) predictors of the same modality as the span task did not outperform predictors of the other modality. We conclude that verbal and spatial short-term memory appear to rely on similar processes when serial recall is required and that developments in span are closely tied to increases in processing speed.