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10. PSYCHOPHYSIOLOGY SECTION
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The main topics of research are still sleep, stress and performance, evoked brain potentials, and portable performance tests. The emphasis has moved from stress towards sleep in response to an increase in extramural support for our work.
10.1 Sleep (Wilkinson, Campbell, Tilley, Warren, Whitten)
An important part of the Section's work is the recording of people's sleep in the natural setting of their own homes. Three measures are taken, each with some credentials as a measure of the quality of sleep; the physiological record of sleep (electro" encephalogram, electro-oculogram, and electrocardiogram), subjective report, and performance the next day. This work allows us to examine the fundamental question of how well they agree, while still responding to issues of current concern. One branch of this research is funded by The Commission of European Communities to study The Effect of Traffic Noise on Sleep in the Home. Work had started by the end of the last progress report and has continued throughout the period of the present one. Fifteen people have been recorded for 16 nights each, all living beside arterial roads having almost continuous traffic all night. The main variable has been to add double glazing to the bedroom windows, reducing the noise inside by about 10 dbA. Significant effects have been observed on all three kinds of measure. Now we are trying to establish broadly the level and spectra of traffic noise peaks which disrupt sleep physiologically, or produce outright wakefulness. We find that people vary greatly in what disturbs them, which underlines the need to follow this study with a more detailed examination of particular groups at risk. Several papers have been published so far (57; 59; 60; 259; 256).
The second study of sleep in the home was upon the Sleep of Shift Workers, a two-year project commissioned by the European Foundation for the Improvement of Living and Working Conditions (216; 220). Important differences were found between sleep during a week on the night shift and sleep during the normal day shifts. Performance on the night shift was also worse than during the day. The men were working a three-shift system, changing shifts every week. Future research, if funded, will examine systems which change either more rapidly or more slowly, including permanent night shift, in order to identify those patterns of working which are least harmful to sleep and performance.
In the laboratory we have examined the effect of one night's loss of sleep, first upon retrieval from long-term memory as a function of the familiarity, or dominance, of the items recalled and second, on "R/S refractoriness", the lengthening of choice serial reaction time which occurs when a stimulus follows too closely upon a previous response. This latter study has led to a series of experiments on this kind of refractoriness in which the variables have been number of choices, amount of practice, and duration of the task. Finally, two reviews have been prepared, one on sleep deprivation generally (257) and another on the relationship between body temperature, performance, and the sleep/wake cycle (258).
10.2 Development of portable apparatus for assessing deterioration in skill (Wilkinson, Houghton)
In the long-term project for producing a battery of standardised portable tests, two new tasks, vigilance and short-term memory, have been added. Both work well, but the short-term memory task appears to be little affected by environmental stress. The Unprepared Simple Reaction Time test (mentioned in the previous progress report) is now used widely and has proved particularly satisfactory on grounds of its sensitivity to stress and the stable plateau of normal performance it provides following minimal practice. Efforts have been devoted therefore to producing a portable microprocessor-card version of the test which stores reactions times in digital memory (rather than cassette tape) and can analyse data and display results on the spot.
10.3 Event-related changes in the brain as correlates of attention (Wilkinson, Campbell, Allison)
In one experiment now in progress, refractoriness of the evoked potential is being examined as a function of attention to the stimuli concerned. In another, a reaction time experiment, we are attempting to distinguish those event-related changes in the EEC which are due to the response from those due to the stimulus. Meanwhile the results of an evoked potential study of signal detection have been published (255) and Campbell has completed a study of personality in relation to auditory brain stem evoked potentials (55). Campbell has also contributed two substantial reviews, one on clinical studies of the auditory brain stem evoked potential (58), and the other dealing with the evoked potential correlates of human information-processing (56).
10.4 Effects of environmental stresses
10.4.1 Memory (Millar)
In one of three experiments on memory, Millar examined the hypothesis that noise impairs short-term recall by masking inner speech (144). This was done by varying the ability to rehearse the list to be remembered. The hypothesis was supported, but with reservations. Then he studied retrieval from long-term memory as a function, first of noise (146) and then time of day (147). Performance was found to be best later in the day, unlike that of short-term recall which is thought to be superior in the morning.
10.4.2 Effects of single and combined environmental stresses (Wilkinson, Millar)
Three studies have been carried out in collaboration with outside establishments. At the Hammersmith Hospital, Department of Anaesthetics, we had previously shown that performance of patients was impaired throughout the day following minor surgery in the morning (209). This is thought to be due mainly to the after-effect of anaesthesia. A further study has compared this recovery rate for different anaesthetic agents.
A drug study has been supported by Pharmax Ltd. in which the portable tests of vigilance and reaction time were used to assess the side effects (drowsiness) of a common antihistamine preparation and show how well an ephedrene-based additive could counteract this effect (145). The additive was approved.
In a joint study with the School of Hygiene and Tropical Medicine, the reaction time test was used to investigate industrial pollution 61). Paint sprayers in a boat factory were compared with control workers from the same plant for possible adverse effects of styrene present in the spray.