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Biomedical subjects

R T Wilkinson

Publications and source records attributed to R T Wilkinson.

At least 19 recordsLinked to original sources
PubMed1992

How fast should the night shift rotate?

Claims are frequently made that changing from morning to afternoon to night shift at about two- to three-day intervals (rapid rotation) is the best way of organizing 24h staffing. A critical analysis is made of the grounds for these assertion, followed by a review of evidence bearing upon the issue of whether longer periods of rotation are to be preferred. The conclusion is that permanent (zero rotation), fixed-night systems are superior on most counts, and should be implemented for night work, leaving the option of rapid rotation to cover the two (morning and afternoon) day shifts. This said, the multiplicity of shift systems and settings means that this will not always be the method of choice. Furthermore the recommendation should be regarded as provisional pending a search for more data directly comparing the two systems.

Adult↗
PubMed1990

Response-stimulus interval in choice serial reaction time: interaction with sleep deprivation, choice, and practice.

In choice serial reaction time (RT), Response-to-next-Stimulus Interval (RSI) was varied from 0 to 600 msec in 40-msec steps. In three experiments, RT fell and errors rose as RSI was increased to 480 msec; they remained unchanged thereafter. The effect of RSI on RT was not linear, was reduced by 6- as compared with 4- or 3-choice responding, and was unaffected by sleep deprivation, despite loss of sleep reducing RT overall. The effect of penultimate RSI on RT was similar to that current RSI, but smaller. Two explanations of RSI--response-generated kinaesthetic feedback blocking a "central processor" and a preparatory interval as in warned simple RT--are rejected. Instead, the idea of "relative refractory state" is revived but now, because of the RSI/error finding, biased more towards responding than stimulus reception and encoding. In all three experiments the influence of RSI on RT was reduced with practice. If practice encourages automatic rather than controlled processing (Shiffrin & Schneider, 1977), the prediction is that the former will show less refractoriness.

Adult↗
PubMed1989

Age and simple reaction time: decade differences for 5,325 subjects.

In a booth at a public exhibition entitled "Medicines for Man," 5,325 men, women, and children carried out a 1-minute test of simple reaction time (RT) with 1 to 10 second randomized variable preparatory interval (PI). They recorded their ages by decade. Average RT over the last eight (of ten) trials increased progressively from the 20s up to age 60 and over, and downward to the teens and under 10s. The single fastest RT in each test varied much less with age, only the 20s being clearly faster than the rest, with the under 10s slower. Within-subject variability of RT was increased only in the under 10s and over 60s. Ability to sustain attention during the longer PIs may underlie the gross average RT differences with age, and possibly some more basic neural property the superiority of the 20s in fastest RT.

Adolescent↗
PubMed1989

The detection of sleep onset: behavioral, physiological, and subjective convergence.

In this report, a sleep deprivation/multiple arousal paradigm was used in which response time (RT) and respiratory and electroencephalographic (EEG) measures were combined with a continuous behavioral index of arousal (a deadman switch) and frequently repeated Stanford Sleepiness Scale ratings to examine the process of falling asleep. Sleep was defined behaviorally as failure to respond to the faint auditory RT cue. Although response rates decreased significantly as EEG stages passed from W through 1 to 2, responding continued in both light "sleep" stages. Respiratory, subjective, and DM changes were more pronounced between Stages W and 1 than between Stages 1 and 2. If the criterion for wakefulness is cognitive response to external stimulation, accurate distinctions between sleep and wakefulness can only be made in EEG Stages 3, 4, and rapid eye movement sleep. If EEG is the criterion, then the data suggest that cognitive response is possible during Stages 1 and 2 "sleep". The concept of a Sleep Onset Period, characterized by lengthening response times and intermittent response failure (thereby reflecting neither true sleep nor wakefulness), may provide a useful resolution to this definitional dilemma.

Adult↗
PubMed1988

Behavioral versus EEG-based monitoring of all-night sleep/wake patterns.

Faint tones were presented at intervals (average 16 s) throughout a night's sleep; whenever they heard them, subjects pressed a palm-mounted button to switch them off. At the same time, electroencephalogram (EEG) was recorded. Button-press responses occurred in all EEG stages of sleep except Stage 4, although there was only one behavioral response (BR) in Stage 3 and one in REM. The mean probability of response (PR)/Stage was Stage 1 = 0.235, Stage 2 = 0.016, Stage 3 = 0.001, Stage 4 = 0.000, Stage REM = 0.0004. Also, responses sometimes failed to occur in EEG Stage wake (PR = 0.94), particularly near sleep onset. If the criterion for wakefulness is cognitive response to external stimulation, only in EEG Stages 3, 4, and REM can accurate distinctions between sleep and wakefulness be made. If EEG is the criterion, then the data suggest that cognitive response is possible during Stages 1 and 2 "sleep." The concept of a sleep onset period (SOP), characterized by lengthening response times and intermittent response failure (thereby reflecting neither true sleep or wakefulness), may provide a useful resolution of this definitional dilemma.

Acoustic Stimulation↗
PubMed1979

A portable pulse-interval modulation telemetry/multiplexing EEG recording system for use in the home.

A portable 6-channel recording system employing time-division multiplexing with cable or radio-telemetry has been developed. The system is very compact and has proved to be reliable when used in a domestic environment. The use of multiplexing, in general, permits an expansion in the number of available channels and a reduction in equipment and tape costs, while the use of pulse interval modulation, in particular, overcomes tape recording limitations which may be encountered with the more common amplitude modulation techniques.

Electroencephalography↗
PubMed1978

EEG event-related potentials and signal detection.

The purpose of this study was to determine whether certain previously reported relationships between event-related potentials and measures of signal detection performance occur in vigilance as well as psychophysical settings. In the course of the study, evidence was found which challenges previously proposed psychological correlates of "P300". EEG was recorded while 15 subjects carried out a 40-min signal detection test. CNV was measured between a warning click and the brief offset of a dim light denoting the possible (p = 0.5) occurrence of the signal, a faint tone in the constant background noise. P300 was measured at a point 300 msec following offset of the dim light. As reported previously in psychophysical settings, P300 amplitude was positively related to signal intensity and response confidence, and was larger for correct detections (Hits) than for correct rejections, misses or false alarms. From first to second half of the test both Hits and false alarms fell, response criterion beta rose, and the amplitude of both CNV and P300 fell. The latter negative relationship between beta and P300 contrasted with a positive one when subjects rated their signal reports at three levels of confidence; here the most confident ratings (high beta) were associated with the highest amplitude of P300. CNV reflected individual ability to sustain performance. Results are explained in terms of a two-factor version (Wilkinson, 1976) of the prior state/reactive change hypothesis (Karlin, 1970). It is suggested that time on task constitutes a prior state influence on P300, whereas other variables influence P300 by means of either reactive change or 'real' change in an endogenous P300 component.

Adult↗
PubMed1978

Effects of sleep deprivation on short duration performance measures compared to the Wilkinson auditory vigilance task.

The effects of one night's total sleep deprivation were examined using the Wilkinson vigilance task and four 10 min duration performance tests. A repeated measures design was used in which eight male subjects experienced one night of sleep loss, the order of sleep loss being balanced across subjects. The four short duration performance tests consisted of choice reaction time, simple reaction time, short-term memory, and a motor task, handwriting. The results confirm the effects of one night's sleep deprivation on the vigilance task and also show that performance on the two reaction time tests was significantly impaired by the loss of sleep, but not at such a high level as for the vigilance. The short-term memory test failed to show any adverse effects of sleep loss and similarly for the handwriting. The experiment shows that two portable and brief (10 min) performance tests are sensitive indices of sleep loss and should be particularly useful for assessing levels of alertness in the field.

Adult↗
PubMed1976

Residual effects of hypnotic drugs: evidence for individual differences on vigilance.

Twelve healthy volunteers were given butobarbitone 100 and 200 mg, nitrazepam 5 and 10 mg and 2 lactose dummy treatments, at 23.00 hours at weekly intervals over 6 weeks according to a balanced design and using double blind conditions. Performance was studied between 09.00 hours and 17.00 hours the following day. Significant (P is less than 0.05) impairment of tapping rate and digit symbol substitution occurred. No significant differences occurred between performance after active drug and dummy in auditory vigilance, and subjective effects. Examination of individual differences in the response of subjects to the 4 hypnotic drug treatments, compared with their responses after dummy, indicated that subjects could be divided into two groups. One group consistently rated themselved as more alert after hypnotics and their vigilance performance improved. The other group consistently were more drowsy after hypnotics and their performance was impaired. It is suggested that the improvement in the first group resulted from improved sleep quality sufficient to counteract the residual effect of the hypnotic, whereas the second group merely showed the residual effects of the drugs.

Adult↗
PubMed1976

The effects of low doses of amylobarbitone sodium and diazepam on human performance.

The effects of diazepam (2.5 and 5 mg) and amylobarbitone sodium (50 and 100 mg) on performance and subjective effects were assessed in a group of twelve healthy subjects under standardised conditions. Treatments were administered orally at weekly intervals according to a balanced design and under double-blind conditions. The tests of performance most sensitive to drug effects in these healthy subjects were either prolonged and monotonous and gave the subject no feedback on performance, or required short term memory for efficient execution. Auditory vigilance was significantly impaired (P less than 0.05) between 45 min and 1 h 45 min after all drug treatments except amylobarbitone sodium (100 mg), compared with performance after lactose. At the same time false reports were significantly increased after amylobarbitone sodium (100 mg) compared with all other active drugs but not with lactose. These effects had disappeared 4-5 h post drug. Short term memory was impaired 1h 45 min after all treatments and impairment was dose related. No significant effects occurred 5h after treatment. Simple auditory reaction time was prolonged 2 h after the highest doses of amylobarbitone sodium and diazpam, and by amylobarbitone sodium (50 mg) 5 h 15 min after treatment. At this time the effects of diazepam had worn off. Digit symbol substitution was impaired by amylobarbitone sodium (50 and 100 mg), and diazepam (5 mg) after 2 h 45 minutes. No significant changes in visual search or tapping occurred after active drugs compared with lactose. Subjective ratings indicated both mental and motor impairment 2 h 45 min after all active preparations compared with scores after lactose though significant changes followed diazepam (2.5 mg) infrequently. Both correct detections and false reports in auditory vigilance tended to fall over the 6 separate days of testing, indicating an increase in caution. Visual search, short term memory, tapping and digit symbol substitution significantly improved with time, but there was no change in reaction time. From the limited information obtained by sampling blood at 3 and 6 h, no relationship between change in performance and plasma level was found in these subjects.

Adult↗