Sleep/wake regularity and cognition in college students using antidepressants.

The current project examined sleep, sleep/wake regularity, and cognition in college students diagnosed with depression and using serotonergic antidepressants and in those without a depression diagnosis. Forty participants either using antidepressants (n = 20, 24.75 ± 6.82 years) or without a depression diagnosis (n = 20, 21.70 ± 2.74 years) wore actigraphs for two consecutive weeks (14 days). Cognitive tasks were completed on day 1 (along with demographic surveys) and day 14. Effect sizes indicated that compared to non-clinically depressed peers, participants using antidepressants exhibited slightly greater wake after sleep onset (d = 0.36) and lower sleep efficiency (d = 0.40); however, these differences were likely not noticed by the sleeper. No sleep regularity or cognitive differences were present between groups. Within the antidepressant group, higher dosage predicted greater time in bed (R2 = 0.77), but less total sleep time (R2 = 0.86). The time of day that participants took their antidepressant exhibited differential effects on certain cognitive parameters, such as procedural reaction time and spatial processing, and interactions with years of antidepressant use were found. Self-reported wake episodes also predicted better reaction time and inhibition in the antidepressant group. This study is the first to demonstrate that sleep/wake regularity is comparable between people using antidepressants and non-clinically depressed human samples. For individuals using antidepressants, years of use, dosage, and time of day of use have predictive qualities for reaction times, spatial processing, and inhibition.

Sex moderates the effects of total sleep deprivation and sleep restriction on risk preference.

Sleep loss has been shown to alter risk preference during decision-making. However, research in this area has largely focussed on the effects of total sleep deprivation (TSD), while evidence on the effects of sleep restriction (SR) or the potentially moderating role of sex on risk preference remains scarce and unclear. The present study investigated risky decision-making in 47 healthy young adults who were assigned to either of two counterbalanced protocols: well-rested (WR) and TSD, or WR and SR. Participants were assessed on the Lottery Choice Task (LCT), which requires a series of choices between two risky gambles with varying risk levels. Analyses on the pooled dataset indicated across all sleep conditions, participants were generally more risk-seeking when trying to minimise financial loss (LOSSES) than while trying to maximise financial gain (GAINS). On GAINS trials, female participants were more risk-averse during TSD and SR, whereas male participants remained unchanged. On LOSSES trials, female participants remained unchanged during TSD and SR, whereas male participants became more risk-seeking during TSD. Our findings suggest the relationship between sleep loss and risk preference is moderated by sex, whereby changes in risk preference after TSD or SR differ in men and women depending on whether the decision is framed in terms of gains or losses.

Normative data for evaluating mild traumatic brain injury with a handheld neurocognitive assessment tool.

The BrainScope Ahead 300 is designed for use by health care professionals to aid in the assessment of patients suspected of a mild traumatic brain injury. The purpose of the current study was to establish normative data for the cognitive test component of the Ahead 300 system and to evaluate the role of demographic factors on test performance. Healthy, community-dwelling adults between the ages of 18 and 80 recruited from five geographically distributed sites were administered Android versions of the ANAM Matching to Sample and Procedural Reaction Time tests that comprise the cognitive test component of the Ahead 300 system by trained personnel. Scores were correlated with age, education, and race. Age accounted for the majority of the variance in test scores with additional significant, but minor, contributions of education and race. Gender did not account for a significant proportion of the variance for either test. Based on these results, the normative data for 551 individuals are presented stratified by age. These are the first available normative data for these tests when administered using the Ahead 300 system and will assist health care professionals in determining the degree to which scores on the cognitive tests reflect impaired performance.

Voluntary Sleep Choice and Its Effects on Bayesian Decisions.

This study examines whether voluntary sleep restriction at commonly experienced levels impacts decision making in a Bayesian choice task. Participants recruited were largely traditional age college students from a regional state university (n = 100) and a federal military academy (n = 99; n = 56 and 43, respectively, used in final analysis). Sleep was measured by actigraphy over a one-week period, followed by performance of a decision task. The task involved two sources of information, base rate odds and sample evidence, with subjects asked to make a probability judgment. Results found that subjects with nightly sleep < 6 hr (sleep deprived = SD), relative to those with > 7 hr, placed less decision weight on new evidence, relative to base rate information, in making difficult choices. This result is strongest among female subjects. For easier choices, voluntary SD did not affect relative decision weights placed on the two sources of available information.

The effects of chronic marijuana use on circadian entrainment.

Animal literature suggests a connection between marijuana use and altered circadian rhythms. However, the effect has not yet been demonstrated in humans. The present study examined the effect of chronic marijuana use on human circadian function. Participants consisted of current users who reported smoking marijuana daily for at least a year and non-marijuana user controls. Participants took a neurocognitive assessment, wore actigraphs and maintained sleep diaries for three weeks. While no significant cognitive changes were found between groups, data revealed that chronic marijuana use may act as an additional zeitgeber and lead to increased entrainment in human users.

A discriminated conditioned punishment model of phobia.

Traditionally, the signaled avoidance (SA) paradigm has been used in an attempt to better understand human phobia. Animal models of this type have been criticized for ineffectively representing phobia. The SA model characterizes phobia as an avoidance behavior by presenting environmental cues, which act as warning signals to an aversive stimulus (ie, shock). Discriminated conditioned punishment (DCP) is an alternative paradigm that characterizes phobia as a choice behavior in which fear serves to punish an otherwise adaptive behavior. The present study quantifies the differences between the paradigms and suggests that DCP offers an alternative paradigm for phobia. Rats trained on either SA or DCP were compared on a number of behavioral variables relevant to human phobia. Results indicate that rats in the DCP paradigm responded significantly earlier to warning signals and were more effective at preventing shocks than rats in the SA paradigm. Implications of this alternative paradigm are discussed.

Effects of power frequency electromagnetic fields on melatonin and sleep in the rat.

BACKGROUND: Studies investigating the effect of power frequency (50-60 Hz) electromagnetic fields (EMF) on melatonin synthesis in rats have been inconsistent with several showing suppression of melatonin synthesis, others showing no effect and a few actually demonstrating small increases. Scant research has focused on the ensuing sleep patterns of EMF exposed rats. The present study was designed to examine the effects of extremely low power frequency electromagnetic fields (EMF) on the production of melatonin and the subsequent sleep structure in rats. METHODS: Eighteen male Sprague-Dawley rats were exposed to a 1000 milligauss (mG) magnetic field for 1 month. Urine was collected for the final 3 days of the exposure period for analysis of 6-sulphatoxymelatonin, the major catabolic product of melatonin found in urine. Subsequent sleep was analyzed over a 24-hour period. RESULTS: Melatonin production was mildly increased in exposed animals. Although there were no statistically significant changes in sleep structure, exposed animals showed slight decreases in REM (rapid eye movement) sleep as compared to sham (non-exposed) animals. CONCLUSIONS: Power frequency magnetic fields induced a marginally statistically significant increase in melatonin levels in exposed rats compared to control. Subsequent sleep analysis indicated little effect on the sleep architecture of rats, at least not within the first day after 1 month's continuous exposure. Varying results in the literature are discussed and future research suggested.