Summary A novel animal‐analog of the human psychomotor vigilance task (PVT) was validated by subjecting rats to 24 h of sleep deprivation (SD) and examining the effect on performance in the rat‐PVT (rPVT), and a rat multiple sleep latency test (rMSLT). During a three‐phase (separate cohorts) crossover design, vigilance performance in the rPVT was compared with 24 h SD‐induced changes in sleepiness assessed by polysomnographic evaluation and the rMSLT. Twenty‐four hours of SD was produced by brief rotation of activity wheels at regular intervals in which the animals resided throughout the experiment. In the rPVT experiment, exercise controls (EC) experienced the same overall amount of locomotor activity as during SD, but allowed long periods of undisturbed sleep. After 24 h SD response latencies slowed, and lapses increased significantly during rPVT performance when compared with baseline and EC conditions. During the first 3 h of the recovery period following 24 h SD, polysomnographic measures indicated sleepiness. Latency to fall asleep after 24 h SD was assessed six times during the first 3 h after SD. Rats fell asleep significantly faster immediately after SD, than after non‐SD baseline sessions. In conclusion, 24 h of SD in rats increased sleepiness, as indicated by polysomnography and the rMSLT, and impaired vigilance as measured by the rPVT. The rPVT closely resembles the human PVT test widely used in human sleep research and will assist investigation of the neurobiologic mechanisms that produce vigilance impairments after sleep disruption.

The anteroventral thalamic nucleus (AV) has a role in spatial memory, but the influence of the prominent brainstem cholinergic projection to this region is unknown. Here, spatial memory in a 12-arm radial maze was examined after 0.15 microl bilateral AV infusions of scopolamine. In part one, rats visited six arms singly (the phase 1 arms) and, after a 10 min delay, were allowed free choice to both phase 1 arms and the remaining six baited arms (phase 2 arms). Scopolamine (10 microg) administered during the delay increased errors to both phase 1 and phase 2 arms, whereas PBS infusions increased phase 1 arm errors only. The PBS effect was the result of inserting the internal cannulas alone and not the infusion. The same dose of scopolamine (10 microg) infused before maze testing (part two: no phase 1 arms, no delay) also impaired spatial memory over and above the effects of both PBS and no-infusion, which did not differ markedly. Part two also showed that choice latency and choice strategies were unaffected by PBS and scopolamine. Cannulation and infusion procedures in both parts one and two did not produce any negative carryover effects across multiple control (no internal cannula) sessions, and a trypan blue manipulation indicated that infusions were restricted to the AV region. This study provides the first direct evidence that the brainstem cholinergic innervation to the limbic thalamus influences learning and memory, which may have important implications for human neurological conditions such as alcohol-related disorders and schizophrenia.

There is often little correspondence between human and animal examples of nondeclarative memory. The serial reaction time task (SRT) is a sequence learning example of human nondeclarative memory that may be suitable for development as an animal model. The SRT is believed to be impaired by basal ganglia, not limbic system damage, but there is uncertainty whether limbic system pathology does in fact leave the SRT unimpaired. We therefore developed a new rat model that closely approximated the human SRT, using intracranial self-stimulation to promote rapid continuous responding to four adjacent nose pokes in a single test session. Intact rats that experienced repeated sequences demonstrated robust interference effects when switched to a random sequence of cued responses (at 4-, 8-, and 12-sequence lengths), unlike intact controls that experienced the random sequences only. The interference effect in the human task is a key measure for nondeclarative sequence learning. Rats with dorsal caudate lesions that experienced massed sequence repetitions showed an interference effect at the four-sequence length only. By contrast, rats with dorsal hippocampal lesions showed an interference effect at all sequence lengths. This new rat SRT model clarifies the basal ganglia-limbic system dichotomy suggested by human work.

Objectives To evaluate the relevance of demographic, physician, and psychological characteristics to PSA screening in ethnic subpopulations and ascertain whether the same characteristics distinguish men who have never had a PSA from those who screen infrequently and those who screen yearly (adhere). Design and methods Stratified cluster‐sampling was used to recruit 533 men (45–70 years) from four ethnic groups: African‐American; European‐American; immigrant Jamaican; and immigrant men from Trinidad and Tobago. Men provided demographic and structural (insurance, regular physician, annual exam, and physician recommendation), cognitive (risk and efficacy perceptions, knowledge), and emotional variables (cancer worry and embarrassment), and reported on PSA screening history. Multinomial logistic regression used these variables to predict three screening classifications (never screened, partially adherent, and adherent). Results Multinomial logistic regression showed that minority men were less likely to report either never screening or yearly screening, while younger men were more likely. Lack of a regular physician (OR=2.87, 95% CI 1.39–5.84), an annual exam (OR=1.73, 95% CI 0.91–3.28), and low recommendation (OR=3.76, 95% CI 2.13–6.66) were associated with being categorized as a never (vs. partially adherent) screener, but only annual exam (OR=0.26, 95% CI 0.10–0.63) was associated with yearly screening. Lower cancer worry was marginally associated with never screening (OR=0.59, 95% CI 0.38–1.04), while knowledge was associated with screening yearly over time (OR=0.46, 95% CI 0.28–0.77). Conclusions Demographic, physician, and psychological variables are differentially associated with never, less than yearly, and yearly screening classifications. Minority men were unlikely to have never screened, but were also less likely to screen yearly. Physician variables were associated with the difference between not screening and partially adherent, but not between partially adherent and yearly screening suggesting that the role of physicians in PSA behaviour over time would benefit from further study.