Parsing attentional components during a simple reaction time task using sleep deprivation and amphetamine intervention

A rodent model of the human psychomotor vigilance test: Performance comparisons

BACKGROUND

The human Psychomotor Vigilance Test (PVT) is commonly utilized as an objective risk assessment tool to quantify fatigue and sustained attention in laboratory, clinical, and operational settings.

NEW METHOD

Recent studies have employed a rodent version of the PVT (rPVT) to measure various aspects of attention (lapses in attention, reaction times) under varying experimental conditions.

RESULTS

Data are presented here to evaluate the short- and long-term utility of the rPVT adapted for laboratory rats designed to track the same types of performance variables as the human PVT-i.e., motor speed, inhibitory control ("impulsivity"), and attention/inattention. Results indicate that the rPVT is readily learned by rats and requires less than two weeks of training to acquire the basic procedure. Additional data are also presented on the effects of radiation exposure on these performance measures that indicate the utility of the procedure for assessing changes in neurobehavioral function in rodents across their lifespans.

COMPARISON WITH EXISTING METHOD(S)

Once stable performances are obtained, rats evidence a high degree of similarity to human performance measures, and include similarities in terms of lapses and reaction times, in addition to percent correct and premature responding. Similar to humans, rats display both a vigilance decrement across time on task and a response-stimulus interval effect.

CONCLUSIONS

The rPVT is a useful tool in the investigation of the effects of a wide range of variables on vigilance performance that compares favorably to the human PVT and for developing potential prophylactics, countermeasures, and treatments for neurobehavioral dysfunctions.

The effects of sleep deprivation on the attentional functions and vigilance

The study of sleep deprivation is a fruitful area of research to increase our knowledge of cognitive functions and their neural basis. In the current work, 26 healthy young adults participated in a sleep deprivation study, in which the Attentional Networks Test for Interactions and Vigilance (ANTI-V) was performed at 10a.m. after a night of normal sleep and again at 10 a.m. after 25.5-27.5 h of total sleep deprivation. The ANTI-V is an experimental task that provides measures of alerting, orienting and executive control attentional functions. Compared with previous versions, the ANTI-V includes a vigilance task, more reliable auditory alerting signals, non-predictive peripheral orienting cues, and also a neutral no-cue condition allowing the analysis of reorienting costs and orienting benefits. Thus, new evidence to evaluate the influence of sleep deprivation on attentional functioning is provided. Results revealed differences in both tonic and phasic alertness after sleep deprivation. Vigilance performance was deteriorated, while a warning tone was more helpful to increase participants' alertness, resulting in slightly faster RT and, in particular, fewer errors. The reorienting costs of having an invalid spatial cue were reduced after sleep loss. No sleep deprivation effect on the executive control measure was found in this study. Finally, since no control group was used, particular precautions were taken to reduce the influence of potential practice effects.

Sleep deprivation and vigilant attention

Sleep deprivation severely compromises the ability of human beings to respond to stimuli in a timely fashion. These deficits have been attributed in large part to failures of vigilant attention, which many theorists believe forms the bedrock of the other more complex components of cognition. One of the leading paradigms used as an assay of vigilant attention is the psychomotor vigilance test (PVT), a high signal-load reaction-time test that is extremely sensitive to sleep deprivation. Over the last twenty years, four dominant findings have emerged from the use of this paradigm. First, sleep deprivation results in an overall slowing of responses. Second, sleep deprivation increases the propensity of individuals to lapse for lengthy periods (>500 ms), as well as make errors of commission. Third, sleep deprivation enhances the time-on-task effect within each test bout. Finally, PVT results during extended periods of wakefulness reveal the presence of interacting circadian and homeostatic sleep drives. A theme that links these findings is the interplay of "top-down" and "bottom-up" attention in producing the unstable and unpredictable patterns of behavior that are the hallmark of the sleep-deprived state.

Vigilance, alertness, or sustained attention: physiological basis and measurement

Vigilance is a term with varied definitions but the most common usage is sustained attention or tonic alertness. This usage of vigilance implies both the degree of arousal on the sleep-wake axis and the level of cognitive performance. There are many interacting neural and neurotransmitter systems that affect vigilance. Most studies of vigilance have relied on states where the sleep-wake state is altered, e.g. drowsiness, sleep-deprivation, and CNS-active drugs, but there are factors ranging from psychophysics to motivation that may impact vigilance. While EEG is the most commonly studied physiologic measure of vigilance, various measures of eye movement and of autonomic nervous system activity have also been used. This review paper discusses the underlying neural basis of vigilance and its assessment using physiologic tools. Since, assessment of vigilance requires assessment of cognitive function this aspect is also discussed.

Effect of sleep deficit, knowledge of results, and stimulus quality on reaction time and response force

Some recent findings suggested that response force measured during reaction time experiments might reflect changes in activation. We performed an experiment in which the effect of sleep deprivation, knowledge of results, and stimulus quality on response force was studied in simple and choice reaction tasks. As expected, both simple and choice reaction times increased with sleep deficit. Further, simple and choice reactions were faster with knowledge of results and slowed down when stimulus quality was degraded. As sleep deprivation affects both arousal and activation, we expected a detrimental effect of sleep on force amplitude. On the other hand, knowledge of results was expected to increase force by its compensatory effect on arousal and activation. No effect of sleep deprivation on response force was found. Knowledge of results increased response force independently of sleep deprivation.

Amphetamine self-administration by humans: modulation by contingencies associated with task performance

The effect of task performance feedback and associated monetary earnings on drug self-administration were evaluated using eight subjects in a residential laboratory setting. The hypothesis was that if subjects believed that d-amphetamine impaired performance and reduced monetary earnings, d-amphetamine self-administration would decrease. Subjects performed computer tasks every day: on certain days that they received capsules, subjects were given bogus feedback regarding their performance ("better" or "worse" than average). On sample days, subjects were required to take d-amphetamine (10 mg BID) or placebo (0 mg BID) capsules. On choice days, subjects could choose between either d-amphetamine or placebo. Subjects received feedback on their task performance on 2 sample days and 2 of 4 choice days. Subjects received no feedback on the remaining two choice days. When subjects received no feedback, they chose d-amphetamine over placebo 78% of the time, and when they were given better feedback messages, they chose d-amphetamine 87.5% of the time. In contrast, d-amphetamine self-administration decreased significantly to 25% when subjects were told that it impaired their performance on work tasks and resulted in reduced earnings. In reality, d-amphetamine had little effect on work task performance. However, compared to placebo, d-amphetamine significantly increased subjective ratings of "Stimulated" and "Good Drug Effect" and significantly decreased ratings of "Tired" and "Sleepy." These results demonstrate that d-amphetamine served as a reinforcer under conditions in which drug self-administration did not influence monetary earnings, but that d-amphetamine self-administration could be modified by feedback/monetary earnings. Thus, contingencies associated with performance have important implications for drug use in the workplace.

Decoupling motor memory strategies: effects of sleep deprivation and amphetamine

The purpose of this study was to examine motor memory strategies using sleep deprivation as a probe. Eighteen healthy men participated in a three-day study in which they underwent repeated testing on a kinesthetic arm position replication task. On the morning of Day 3, after approximately 48 hr sleep deprivation, they ingested either 20 mg d-amphetamine or placebo. Results showed that throughout Day 3 performance remained relatively unimpaired at medial positions for both groups. For positions shifted 25 degrees laterally, accuracy was also relatively unimpaired for the amphetamine group but was compromised for the placebo group. It was concluded that sleep deprivation-induced decrements in positioning ability were due to disruption of kinesthetic memory, a narrowing of attention, or both. Kinesthetic feedback, and encoding and retrieval processes of the spatial reference system were preserved.