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7. PSYCHOPHYSIOLOGY SECTION
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7.1 THE DEVELOPMENT OF PORTABLE APPARATUS FOR ASSESSING DETERIORATION IN SKILL (Project 14) (Wilkinson, Houghton) (terminated 31.3.84)
7.1.1 Field assessment of reduced vigilance
The main achievement of this project has been to produce two small, highly portable, battery-powered devices, one of which presents a Choice Serial Reaction Time (RT) test, and the other a test of Unprepared Simple RT (399), using onboard cassettes to store the data. Software has been written to access these data and analyse them on an Apple microcomputer. These tests have proved highly sensitive to situations which reduce wakefulness and hence impair concentration and attention. The instruments are commercially available and over 400 of them have been bought by establishments wishing to measure these effects objectively in both field and laboratory. Their main application has been in assessing the effects of toxic industrial agents, work schedules in industry and the armed services, abnormal states of sleep, and side-effects of clinical drugs. A prototype microprocessor-based version of the Unprepared Simple RT has also been produced (151), weighing only 650g, including battery. As well as presenting the test and storing all RTs digitally, this device analyses the data and displays the results (mean RT and standard deviation) on the spot.
7.2 WORKING CONDITIONS: PERFORMANCE AFTER REDUCED AMOUNTS OF SLEEP (Project 15) (Wilkinson, Tilley, Ogilvie)
7.2.1 Objective definition of sleep onset
The point of onset of sleep is poorly defined physiologically; this is because efforts to do so have relied mainly on subjective evaluation of sleep onset. Ogilvie and Wilkinson (260) have sought to define this change behaviourally by playing faint 15-sec tones to subjects at irregular intervals as they fall asleep; reasonable cooperation in this was ensured by having them remain awake the previous night. Subjects pressed a button to end each tone as long as they were awake enough to do so. Lack of response was taken as a sign of sleep onset, whereupon the associated physiological changes were noted and the subject wakened for the next trial. Sleep onset was more gradual than expected, and was associated with i) an increase in the ratio of thoracic to abdominal respiration amplitude (259) and 11) the appearance of spindles in the EEG. A second experiment related subjective report and release of a 'dead mans hand' to these indices of sleep onset. In a third study the tones were played throughout a night of sleep. Responses to them provided a clear behavioural picture of the degree and cyclic nature of wakefulness during sleep, with little memory of having responded to any tones by morning.
7.2.2 Quality or quantity of sleep
Tilley (328) restricted subjects to only 4 hours sleep a night, but varied the EEG content by allowing sleep either in the first (2300-0300 hr) or second (0300-0700 hr) half of the night. As expected there were more EEG slow waves (Stage 4] and 'rapid eye movements' (REM) when sleep was taken in the first half of the night. Nevertheless, performance the day after reduced sleep, though worse than normal, was the same whichever half of the night was slept. Thus the recuperative power of sleep in terms of performance appears to depend more on the amount of sleep than upon its composition in EEG terms.
7.2.3 Recovery from loss of sleep
When recovery sleep is allowed following sleep deprivation the amount of slow wave sleep is usually increased in relation to REM. Tilley (325) has shown that this still happens when only the last half of one night is lost, even though this procedure causes much greater loss of REM than of slow wave sleep. Puzzling.
7.3 WORKING CONDITIONS: EFFECT OF SINGLE OR COMBINED ENVIRONMENTAL STRESSES (Project 16) (Millar, Tilley, Wilkinson)
7.3.1 Side-effects of antihistamine drugs
Millar (234) has examined the effectiveness of an additive designed to reduce the drowsiness resulting from a well-known anti-motion-s1ckness pill. Drowsiness was assessed using portable performance tests described elsewhere. The additive was endorsed.
7.3.2 Recovery from anaesthesia
Wilkinson, in collaboration with a team from the Hammersmith Hospital (304), used the portable Choice Serial RT test to trace the time course over two postoperative days of the recovery of vigilance and attention following anaesthesia for minor surgery. Different anaesthetic agents were compared on this basis.
7.3.3 Retrieval from semantic long-term memory
Tilley examined retrieval in a setting which compared the speed with which words of differing familiarity (in -terms of frequency of use in the language) are categorised. Subjects are presented with a target (e.g. the word "apple") and a category (e.g. fruit) and press a 'yes' or 'no' button rapidly to say whether or not the target falls within the category. Familiar targets are categorised faster than less familiar ones, such as 'mango'. The research confirmed previous findings that the disadvantage of unfamiliar words Is increased when the test is carried out at a low point in the circadian arousal cycle, in this case 0300 (327), and made the further point that when arousal is low the strategy for identifying unfamiliar items as not belonging to the category is changed to one which economises in effort but at the expense of overall efficiency (326).
7.4 INDIVIDUAL DIFFERENCES IN RESPONSE TO STRESS; NOISE AND PERFORMANCE (Project 52) (Ryder, Wilkinson)
7.4.1 Noise and Performance
Research on noise effects on performance has generally produced equivocal results. Increments, decrements and no effect on performance in noise have all been reported. One hypothesis considered is that the range of findings could be due to a small group who are 'noise sensitive'. To test this a group of subjects were intensively studied on a battery of performance tests. Moderate level intermittent noise was used in a simulated office environment.
No significant individual differences were found, and there was little consistency in noise effects over repeated testings. This was true even when significant overall noise effects were found, as was the case with the Sternberg memory comparison task. This test showed significant noise, time of day and interaction effects (300 U). The Implications of these results will be considered in more detail in a further study.
Other results from the main study include a number of significant time of day effects on performance and interactions of noise with time of day.
7.5 THE PHYSIOLOGICAL CORRELATES OF PERFORMANCE UNDER STRESS: EVENT-RELATED CHANGES IN THE BRAIN AS CORRELATES OF ATTENTION (Project 17) (Allison, Wilkinson)
7.5.1 Endogenous event-related potentials (ERP) in the EEG - specific or nonspecific?
Do ERPs reflect primarily the activity of specific cognitive mechanisms in the brain, or are they mainly the expression of changes in nonspecific background activation, in response to varying attentional states associated with cognitive activity? Wilkinson and Allison have carried out three experiments (396; 397a) to examine these potentials in a setting of unprepared reaction time, either one- or two-choice (the cognitive variable), and under conditions of normal sleep or 30-hr sleep deprivation (the variable thought likely to influence the level of nonspecific activation). Loss of sleep reduced the amplitude of the components concerned, suggesting that ERPs do indeed respond to nonspecific factors; this may account at least partly for their changes in association with cognitive behaviour. Further analysis will show whether they also respond to choice in terms of amplitude or latency.
7.5.2 Energy Conservation (Batten, Wilkinson)
In assessing the efficiency with which the energy fed into a house achieves given levels of temperature, ventilation, and dryness, much is known of the contribution of physical variables such as building parameters and environmental influences. Much less is known about the Influence of human behaviour, particularly in the use of the heating controls, ventilation and doors and their effect on this energy equation, and also the occupant's comfort requirements for both temperature and ventilation.
This project is making a preliminary enquiry into the influence of such behavioural variables. More specifically, we have recorded energy (gas + electricity) consumption and internal temperatures, and monitored a variety of behavioural parameters quarter-hourly over 2 separate weeks In 8 virtually identical gas-centrally-heated terraced houses. The behavioural aspects include activity, clothing, comfort and discomfort, and control of heating, doors, and windows.
The very large amount of data collected is being analysed to discover how particular forms of behaviour and control strategies influence the amount of energy consumed in relation to the temperatures and ventilation found. From a more theoretical point of view, comfort votes are being analysed in relation to temperature, clothing and metabolic rate (inferred from the activity data) to determine whether Fanger's general function intended to predict conditions of ideal comfort hold good in this longitudinal study under actual residential conditions.
7.6 CLINICAL PSYCHOPHYSIOLOGY (Project 47) (Ryder)
7.6.1 Computed Axial Tomography (CAT) in schizophrenia
The advent of computed axial tomography (CAT) allows non-invasive measurement of neuroanatomical structures. Recent research reporting increased incidence of ventricular enlargement and of anomalies in neuroasymmetry in schizophrenic patients has raised considerable interest -in the potential use of the CAT technique in psychiatric settings. However the validity and utility of measures derived from CAT scanning remain equivocal.
Preliminary findings in the area suggest that the CAT technique may refine our conceptualization of schizophrenia In terms of aetiology, diagnosis, prognosis and treatment. Ventricular enlargement, which appears to be related to negative symptomatology and poor prognosis, may indicate a distinct clinical subgroup. Research on neuroanatomical asymmetry using CAT scanning offers a new method for investigating the relationship between structural and functional asymmetry. Studies in this area are put in context and implications for future research are considered by Ryder in two review papers (297 U; 298 U).
7.7 THE EFFECTS OF NOISE AND SHIFTWORK ON SLEEP (Project 30) (Campbell, Tilley, Wilkinson)
7.7.1 Effects of traffic noise on sleep in the home
Wilkinson and Campbell (71; 391; .398) have reported the main results of this long-term study of the sleep over 5 weeks of 12 people who live on urban arterial roads carrying very heavy traffic at night. Installing double glazing in the bedroom improved the subjectively reported quality of sleep and also performance the next morning. Although many EEG measures were unaffected, low frequency activity (EEG Stage 4), thought to reflect deep sleep, was increased by the sound attenuation. Significant, though small, cardiovascular changes were also noted (397). More recent work has emphasised individual differences in susceptibility to noise-induced disturbance of sleep. This literature has been reviewed (392), and each subject's records have been analysed individually (393) as follows: The EEG was scored visually for signs of arousal following noise peaks. These were compared, as a control, with similar measurements made at random during the same night. Significantly greater disturbance of sleep by the real noise peaks was demonstrated in two of the people studied. Most of the other ten showed little effect. A similar analysis based on heart rate showed no reliable effect of noise peaks on any of the subjects (394). Overall we conclude that in the population as a whole traffic noise may have a tonic effect of preventing sleep from reaching its normal depth. In a few people, however, there may be an acute effect in which individual peaks can repeatedly cause arousal to a greater or lesser degree. The health of these people may well be at risk if circumstances compel them to live in such noisy surroundings.
7.7.2 Shiftwork
A final report (330) has been published by Tilley and Wilkinson on the large scale project funded by the CEC to examine how far daytime sleep on the night shift is degraded as compared with normal night-time sleep. Considerable impairment was found, suggesting progressive sleep deprivation during a week on the night shift, a conclusion reinforced by a steady decline in performance on portable vigilance tests during the week on 'nights' as compared with dayshift weeks. The techniques of measurement developed appear sufficiently rigorous to support a comparative examination of some shift systems in current use in search of those least prejudicial to sleep.
Other sections in the 1981-1984 report
2. COGNITIVE PSYCHOLOGY
3. COGNITIVE ERGONOMICS/APPLIED COGNITIVE PSYCHOLOGY
4. HEARING
5. MOTOR SKILL AND ACTION
6. VISUAL PERCEPTION
7. PSYCH0PHYSIOL0GY SECTION