Sleep deprivation impairs the accurate recognition of human emotions

Sleep. 2010 Mar 1;33(3):335-42.
van der Helm E, Gujar N, Walker MP.
Sleep and Neuroimaging Laboratory, Department of Psychology, University of California, Berkeley, CA 94720-1650, USA.

Study objectives: Investigate the impact of sleep deprivation on the ability to recognize the intensity of human facial emotions.

Methods: Randomized total sleep-deprivation or sleep-rested conditions, involving between-group and within-group repeated measures analysis. Thirty-seven healthy participants, (21 females) aged 18-25 y, were randomly assigned to the sleep control (SC: n = 17) or total sleep deprivation group (TSD: n = 20). Participants performed an emotional face recognition task, in which they evaluated 3 different affective face categories: Sad, Happy, and Angry, each ranging in a gradient from neutral to increasingly emotional. In the TSD group, the task was performed once under conditions of sleep deprivation, and twice under sleep-rested conditions following different durations of sleep recovery. In the SC group, the task was performed twice under sleep-rested conditions, controlling for repeatability.

Results: In the TSD group, when sleep-deprived, there was a marked and significant blunting in the recognition of Angry and Happy affective expressions in the moderate (but not extreme) emotional intensity range; differences that were most reliable and significant in female participants. No change in the recognition of Sad expressions was observed. These recognition deficits were, however, ameliorated following one night of recovery sleep. No changes in task performance were observed in the SC group.

Conclusions: Sleep deprivation selectively impairs the accurate judgment of human facial emotions, especially threat relevant (Anger) and reward relevant (Happy) categories, an effect observed most significantly in females. Such findings suggest that sleep loss impairs discrete affective neural systems, disrupting the identification of salient affective social cues.

Impair human episodic memory

Single pulse electrical stimulation of the hippocampus is sufficient to impair human episodic memory.
Neuroscience. 2010 Jul 16
Lacruz ME, Valentín A, Seoane JJ, Morris RG, Selway RP, Alarcón G.

They used the single pulse electrical stimulation (SPES) technique to investigate whether more localized stimulation of the hippocampus can affect human episodic memory. A recognition memory test including words, object drawings, abstract drawings and unfamiliar faces was performed without stimulation (baseline) or synchronized with single 1 ms electrical pulses applied to the left, right or both hippocampi in 12 epileptic patients investigated with bilateral depth electrodes. No differences were found in memory performance between baseline and unilateral stimulation, either in the total score or in material-specific scores. In contrast, bilateral stimulation was associated with a pronounced decrease in the median of total memory scores (57%), and of material-specific sub-scores for words (38%), geometrical drawings (81%) and faces (100%). Additional study of stimulation at presentation of stimuli (encoding) versus the recognition memory (retrieval) test phase, showed only reduction in memory at encoding. The results provide causal evidence that the hippocampi are necessary for supporting episodic memory. The induction of memory deficits by bilateral stimulation with parameters that do not induce effects when applied unilaterally suggests that recognition memory can be processed independently by the hippocampus on either hemisphere

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