Showing papers in "Psychophysiology in 1984"

On the Dependence of P300 Latency on Stimulus Evaluation Processes

Abstract: McCarthy and Donchin (1981) found that the latency of a late positive component of the event-related potential (ERP) was influenced by the presence of noise in a stimulus matrix but not by the compatibility between the stimulus presented and the response required They concluded that this component is a P300 and that its latency was influenced by stimulus evaluation but not by response selection processes The present experiments were designed to confirm that the component identified by McCarthy and Donchin was indeed a P300 and to determine if its latency varies systematically with increases in stimulus evaluation time produced by graded changes in noise level In Experiment 1, subjects performed a standard oddball task in which they were required to count the rarer of two stimuli (the words RIGHT or LEFT) which were, or were not, embedded in a noise matrix (characters from the alphabet) The positive component of the ERP, whose amplitude was larger for rare target stimuli, was labeled a P300, and the latency of this component was longer when the stimuli were embedded in noise In Experiment 2, subjects performed a choice reaction time task Following the procedures used by McCarthy and Donchin, stimulus words RIGHT and LEFT required right or left hand responses depending on the presence of a cue word SAME or OPPOSITE which preceded the stimulus Stimulus words were presented in four different degrees of noise, the levels of which were manipulated by varying the set size of the alphabetic characters which could surround the stimulus words Reaction time increased both with noise (by 325 ms) and as a function of stimulus-response incompatibility (by 127 ms) In contrast, P300 latency increased substantially with noise (by 200 ms) but, to a much lesser extent (by 14 ms), with response incompatibility These results indicate that the P300 is sensitive to the ease with which a target stimulus can be discriminated from noise They confirm that P300 latency can be used as a measure of the timing of stimulus evaluation processes that is relatively independent of response selection and execution

The Endogenous Eyeblink

Abstract: The endogenous eyeblink is identified as a cortically controlled response event, distinguishable from both reflexive and voluntary lid movements. It has a characteristic rate, form, and temporal distribution. These aspects of endogenous blinks are related to cognitive state variables. Allocation of attentional resources, transition points in information processing flow, and possibly processing mode, are indexed by blink parameters.

The Effects of Age on Human Event‐Related Potentials

Abstract: Event-related brain potentials were recorded from 72 normal subjects aged 20-79 yrs. The event-related potential to a detected improbable signal contained a large late positive component or P3 wave. The latency of the P3 wave in the response to an auditory signal increased regularly with increasing age at a rate of 1.36 ms per year, and its amplitude decreased at a rate of 0.18 μV per year. Similar age-related changes in the P3 wave occurred in the visual and somatosensory modalities. The change in the latency of the P3 wave occurred independently of any change in the reaction time, which showed no significant age-related change. The latency of the P3 wave associated with the detection of an omitted auditory stimulus did not change significantly with age.

Short-term habituation and dishabituation of the mismatch negativity of the ERP.

Abstract: Standard tones of 1000 Hz and deviant tones of 1250 Hz were presented in random order, 1 stimulus/second. The probabilities of the standards and deviants were 90% and 10%, respectively. In one condition the subject counted the deviant stimuli and in the other condition he/she read a comic book. ERPs were separately averaged to 1) the standard preceding the deviant, 2) the “first deviant” preceded by at least 4 standards, 3) the “second deviant” (an occasional deviant immediately following the “first deviant”), 4) the first and 5) the second standard following the “first deviant,” 6) the first and 7) the second standard following the “second deviant.” It was found that the mismatch negativity evoked in both conditions by the first deviant was considerably larger than to the second deviant. Also the first standard following the first deviant evoked the mismatch negativity. The results are discussed in terms of parallel neuronal models of the stimuli as reflected by the mismatch negativity.

Heart Rhythm Control During Sleep

Abstract: Heart rate (HR) changes during sleep were analyzed, with the aid of a minicomputer, for a group of 20 healthy subjects. In stages 1, 2, 3, and 4, HR decreased against a background of increasing respiratory arrhythmia. REM sleep was characterized by increased HR and decreased respiratory arrhythmia. HR changes during sleep were dependent on the subject's initial autonomic HR control level. The evidence from 3 healthy subjects, who were studied under baseline conditions, propranolol (a sympatholytic agent), atropine (a parasympathetic depressant), and propranolol plus atropine, showed that the HR decrease during stages 1, 2, 3, and 4 is caused by augmented parasympathetic input. The HR increase during REM sleep is due to a reduction in parasympathetic control. The sympathetic input remains relatively constant throughout all stages of sleep, except for its decrease during stage 1.

Effects of stimulation rate and attribute cuing on event-related potentials during selective auditory attention.

Abstract: Auditory event-related potentials (ERPs) were recorded from subjects who attended selectively to a sequence of tones of one frequency and ignored a comparable sequence of tones having a different frequency and spatial origin. In one condition the tones consisted of randomized sequences of brief tone pips while in a second condition the tones were brief increments in intensity (pedestals) of continuous tones at the two frequencies. The tone pips and pedestals were delivered at comparable interstimulus intervals (ISIs), which were short (250–550 ms) in some runs and long (1250–2750 ms) in others. For both classes of stimuli, the subject's task was to detect occasional “target” tones of a slightly shorter duration than the more frequent “standard” tones. Stimuli of the attended frequency elicited a broad negative ERP component (Nd) relative to the unattended tone ERPs. The Nd wave had a considerably shorter onset latency and was smaller in overall amplitude at the faster rate of stimulation. However, the Nd wave did not differ in latency or amplitude between the tone pip and pedestal conditions at corresponding ISIs, suggesting that a high rate of information delivery is a more important factor in accelerating Nd onset than is the continuous reinforcement of the sensory cues that define the two classes of input.

Intensity and task effects on evoked physiological responses to noise bursts.

Abstract: To compare the sensitivity of a variety of psychophysiological variables to stimulus intensity and attention parameters, we simultaneously recorded EEG, eyeblink, skin conductance, and heart rate responses. Twelve subjects were presented with 50-ms, abrupt onset, white noise bursts of four intensities: 65, 80, 95 and 110 dB SPL. Nineteen stimuli of each intensity were given in random order with ISIs between 12 and 17 seconds. This paradigm was repeated under three randomly ordered task conditions: simple reaction time to the noise bursts, passive sitting, and visual tracking. Response components were evaluated by Principal Components Analysis and peak measurement. Several factors and peaks increased with intensity, including those representing P300 and the Slow Wave. Task also had marked effects on certain components. SCR amplitude decreased rapidly over time, while the amplitudes of P300 and other event-related potentials did not. The findings do not allow the late positive event-related potential components to be classified unambiguously as orienting, defense, or startle responses. Cognitive theories of these components have little predictive power for the observed intensity effects.

Electrodermal Nonresponding, Antisocial Behavior, and Schizoid Tendencies in Adolescents

Abstract: Most studies which have tested the hypothesis of autonomic hyporeactivity in antisocial groups using skin conductance orienting response (SCOR) amplitudes have failed to confirm this prediction. However, frequency measures may represent more stable and complete indices of responsivity than amplitude measures and, therefore, provide a better test of an antisociality-hyporeactive relationship. This possibility was tested by relating electrodermal responding-nonresponding to a series of 65dB tones in 101 15-yr-old males to measures of antisocial behaviour and undersocialization. While SCOR amplitudes were unrelated to antisociality, frequency of response and incidence of nonre-sponding were significantly related in the predicted direction. A second analysis demonstrated antisocial nonresponders to be characterised by schizoid tendencies, but not by sensation-seeking. These data indicate that equating nonresponding with antisociality and interpreting such a relationship in motivational/arousal terms may be over-simplistic, and that it may be specifically a schizoid subsection of antisocials who are characterised by nonresponding. It is hypothesised that the frequently cited link between antisociality and psychosis-proneness may be underpinned by a disturbance of sustained attention as indexed by nonresponding.

Pattern Recognition of Self‐Reported Emotional State from Multiple‐Site Facial EMG Activity During Affective Imagery

Abstract: A multivariate pattern-classification system was developed for the study of facial electromy-ographic (EMG) patterning in 12 female subjects during affect-laden imagery and for posed facial expressions. A parameter-extraction procedure identified the dynamic EMG signal properties which accorded the maximal degree of self-reported emotion discrimination. Discriminant analyses on trialwise EMG vectors allowed assessment of specific EMG-site conformations typifying rated emotions of happiness, sadness, anger, and fear. The discriminability among emotion-specific EMG conformations was correlated with subjective ratings of affective-imagery vividness and duration. Evidence was obtained suggesting that the EMG patterns encoded complex, “blended” reported affective states during the imagery. Classification analyses produced point-predictions of reported emotional states in 10 of the 12 subjects, and provided the first computer pattern recognition of self-reported emotion from psychophysiological responses.

Perceptual and motor space representation: an event-related potential study.

Abstract: The purpose of this experiment was to study the brain potentials generated during spatial tasks related to the “schema corporel” (a mental map of sensory-motor relationships). Seven right-handed subjects performed a choice reaction-time task (Experiment 1), in which the spatial position of a visual stimulus (right or left of a fixation point) was varied independently of the spatial position of the response (right or left hand). The subjects also made self-paced extensions and flexions of the right and left index fingers (Experiment 2). Experiments 1 and 2 were performed with the hands both crossed and uncrossed. Spatio-temporal maps showed that the P300 component elicited by the choice RT situation in Experiment 1 was largest ipsilateral to the hand involved in the response, whether or not the hands were crossed. The later part of the pre-movement potentials during Experiment 2 and the motor potential were significantly larger contralateral to the moving hand under all conditions. Thus this pattern of lateralization can be attributed to the superimposition of a bilateral P300 wave on the asymmetrical motor potential. This suggests that distinct neuronal populations are involved in the generation of these two components. P300 latency and RT reflected the spatial conflict: both were longer when the stimulus and response were on opposite sides than when they were on the same side, even when the hands were crossed. However, the average P300 latency was not increased when the hands were crossed, whereas the average RT was substantially increased. Since the additional time required for programming the movement in the crossed hand situation had no effect on P300 generation, we infer that the P300 does not index this motor programming. However, P300 does reflect the stimulus-response spatial matching, since its latency was delayed by spatial conflict.

Hemispheric Asymmetry and Bilateral Electrodermal Recordings: A Review of the Evidence

Abstract: Bilateral electrodermal recordings are often used in psychophysiological research as a measure of functional hemispheric asymmetry. Although significant differences between left and right hand recordings are reported in the literature, the obtained differences are often in different directions. The purpose of the present paper was to review empirical evidence related to the issue of bilateral electrodermal recordings in research on hemispheric asymmetry. Special reference is made to the current controversy concerning contralateral inhibition vs. excitation or facilitation as the underlying mechanism for reported differences in performance of typical hemisphere-specific tasks. After reviewing the evidence, which is contradictory concerning several of the more critical parameters, the conclusion is that bilateral electrodermal recordings have not been unambiguously related to hemispheric asymmetry. However, when asymmetry between the hands is clearly demonstrated, this reflects an asymmetry in the functioning of the cerebral hemispheres.

Peak alpha frequency of EEG during a mental task: task difficulty and hemispheric differences.

Abstract: To investigate the effect of task difficulty on the alpha wave, bilateral EEGs were recorded from frontal and occipital locations from 5 male and 5 female students while they were engaged in two arithmetic (simple addition, SA, and complex addition, CA) and two visuo-spatial (visual imagery, VI, and mental rotation, MR) tasks. During both the arithmetic and the visuo-spatial tasks, peak alpha frequency of power spectrum increased significantly above the resting level. Moreover, the frequency shift was significantly larger in the CA and MR conditions than in the SA and VI conditions. The shift increased as the task difficulty increased. A hemispheric effect was found: the peak alpha frequency increased in the left rather than in the right during the arithmetic tasks whereas it increased in the right rather than in the left during the visuo-spatial tasks.

Aerobic Fitness Affects Cardiovascular and Catecholamine Responses to Stressors

Abstract: Subjects of varying degrees of aerobic fitness were subjected to four laboratory stressors in a test of the hypothesis that aerobic fitness is associated with decreased responsiveness to stressors other than exercise. Blood pressure, heart rate, norepinephrine, epinephrine, and psychological responses to a film of industrial accidents (passive psychological stressor), the Stroop word color task (active psychological stressor), the cold pressor test (passive physical stressor), and running to exhaustion on a treadmill (active physical stressor) were measured. Baseline systolic blood pressure and relative diastolic responses to the film, Stroop task, and exercise were smaller in fit subjects over 40 than in less fit subjects of the same age group. Heart rates were lower in fit subjects at most times, except during and after maximal exercise. Norepinephrine was lower after 9 min of exercise in fit subjects, but was much higher at exhaustion, after these subjects had accomplished more work. Norepinephrine levels fell rapidly and were not different among groups 3 and 10 min after exercise. There was no preferential generalization of the “fitness effect” to the active psychological task.

The detection of sleep onset: behavioral and physiological convergence.

Abstract: Reaction time (RT), a behavioral measure of arousal, was used to examine standard criteria (Rechtschaffen & Kales, 1968) for assessing sleep onset (SO) and the sensitivity of changes in respiratory patterns at SO. Following 24 hrs without sleep, RT, respiratory, and EEG measures were used to study SO in 12 subjects. Sleep deprivation (SD) permitted multiple examinations of SO in 2 daytime testing periods. Strong relationships between RT and EEG-based measures of SO serve to confirm the distinction between wakefulness and stage 1 sleep, and moderate to weak correlations between RT and respiratory indices describe the usefulness of the latter. Behavioral, respiratory and EEG assessments of the shift from wakefulness to sleep were observed to be orderly and rapid in these SD volunteers, suggesting that the detection of SO could be sharpened by adding behavioral and respiratory measures to the usual EEG criteria. The close temporal correspondence among these changes has interesting implications for sleep/waking mechanisms.

Effects of methylphenidate on young adults' performance and event-related potentials in a vigilance and a paired-associates learning test.

Abstract: Twenty-two normal young men received a counterbalanced and double blind administration of 20 mg methylphenidate and placebo. Two tasks were administered in counterbalanced order: an uninterrupted 45-min vigilance test and a paired-associates learning test. As previously reported, under placebo, accuracy and speed decreased monotonically over the course of the vigil. This degradation of performance was significantly reduced by the stimulant drug. Event-related potentials (ERPs) were derived for correctly detected targets and nontargets. The most salient pharmacologic effects involved a late positive wave (P464) identified as P3b. Methylphenidate reversed or reduced the decrease in amplitude and increase in latency of P464 present over phases of the placebo session. The results suggest that the stimulant-induced improvement in performance may be mediated by enhancement of evaluation processes. In the paired-associates test there were no pharmacologic effects. Instead there was an unexpected, pronounced improvement in learning in the second session, irrespective of the substance administered. However, the ERP evoked by the “stimulus” cue of each pair was systematically related to the achievement of learning criteria. A late positive was identified as P3b (P555) increased significantly in amplitude following the attainment of learning. There were no amplitude changes among ERPs evoked in the early post-criterion, late post-criterion, or overlearning “phases.” Nor were there amplitude changes between early and late pre-criterion categories. Thus, ERP amplitude displayed a binary association with the achievement of learning.

Cognitive brain potential components in adolescents.

Abstract: Event-related potentials (ERPs) were recorded in a cross-sectional study from 70 adolescents ranging in age from 11 to 18. A paradigm was used in which background, standard auditory events (66 percent occurrence) were randomly replaced by either a change in pitch, or a missing stimulus, each occurring 17 percent of the time. Subjects were instructed to respond to one of the infrequent events, with each designated as relevant (i.e., a target) on alternate blocks of trials. Factor score analyses showed that P300 and frontal negative slow wave were larger to relevant than irrelevant events, whereas parietal positive slow wave was not. Both N200 and frontal negative slow wave showed modest age effects. Significant effects of sex, mainly for the exogenous components, were also found. These data highlight the importance of the negative task-related potentials as correlates of development. They also point to the functional independence of P300 and slow wave and add to the evidence for the functional distinction between the frontal negative and parietal positive aspects of slow wave.

Innocence, information, and the guilty knowledge test in the detection of deception.

Abstract: The purpose of this detection of deception experiment was to study the assumption of the Guilty Knowledge Test that subjects with guilty knowledge will be classed as guilty by the test regardless of their actual guilt or innocence. Prior to a polygraph examination, three groups of innocent subjects were given the same crime-relevant information as members of a group guilty of a mock crime. These innocent subjects either witnessed the crime, were told the crime details, or carried out innocent activities involving crime-relevant information. An additional group of innocent subjects had no crime-relevant information. Analysis of the Guilty Knowledge Test results showed that the detection scores of guilty subjects were higher than those in any of the innocent groups. In fact, with the exception of the innocent activities group, the innocent informed subjects did not differ from those in the uninformed group. The major conclusion is that subjects may have crime-relevant information and not be classed, based on the detection scores, as guilty.

The Effects of a Restricted Sleep Regime on the Composition of Sleep and on Performance

Abstract: This study examined the effects of restricting sleep to the first or second half of the night on the composition of sleep and on performance. Eight young women who regularly slept for 8–8.5 hrs a night had their sleep restricted to the first or second half of the night for two consecutive nights. Performance of a 20-min unprepared simple reaction time task was measured at fixed times of day for the two restricted sleep conditions and for a full night sleep control condition. Restricting sleep to the second half of the night produced higher amounts of REM sleep and Stage 4 sleep and lower amounts of Stage 2 sleep compared to restricting sleep to the first half of the night. Both restricted sleep conditions impaired performance relative to the full night sleep control, and performance was worse after two nights of restricted sleep than after one night of restricted sleep. The results show that the effects of a restricted sleep regime on the composition of sleep are partly a function of the time of night to which sleep is restricted. It is suggested that the performance deficits are due to loss of sleep per se rather than due to any change in the composition of sleep.

Duration and Placement of Sleep in a “Disentrained” Environment

Abstract: Sleep/wake cycles of 9 young adults were electrographically recorded during 60 hrs of enforced bedrest. During this period subjects were required to lie quietly, with no time cues and minimal exogenous stimulation. Sleep and wakefulness patterns were clearly modified under these conditions. There was an alternation of waking periods with an average length of 2.7 hrs and sleep episodes with a mean duration of 2.99 hrs. Eighty percent of both sleep and waking periods were less than 4 hrs duration. The circadian pattern of sleep period duration persisted in disentrainment, but temporal organization of sleep episodes was substantially disrupted; sleep episodes occurred throughout the 24-hr day. The results suggest the presence of two distinct components of the human sleep system–one, sleep duration, is controlled by an endogenous circadian oscillatory system; another, sleep placement, is controlled primarily by behavioral controls, in the form of social and occupational pressures, and self-imposed behavioral alternatives to sleep.

Laterality, Emotionality, and Heartbeat Perception

Abstract: Recent research on visceral perception has indicated that hemispheric specialization and emotionality may account for individual differences among subjects. The present study was designed to examine the nature of the relationship between hemispheric specialization and emotionality, and the manner in which these variables influence individual differences in visceral perception (i.e., detection of cardiac activity). Male subjects were given 20 questions used to test lateral eye movements. Following the completion of the State-Trait Anxiety Inventory (STAI), Form X-1 (State Anxiety), cardiac awareness was assessed using the Whitehead heartbeat discrimination procedure. Subjects then completed the STAI, Form X-2 (Trait Anxiety), and the Eysenck Personality Inventory. Results indicated that good heartbeat perceivers made significantly more left lateral eye movements (i.e., right hemisphere preferent) than poor perceivers on any of the emotional indicators. It was found, however, that subjects with high scores on two of the three emotional indicators made significantly more left lateral eye movements than subjects with low scores. Additional analyses indicate that respiration rate and subject obesity may affect the ability to detect feedback of cardiovascular function.

Task difficulty, type A behavior pattern, and cardiovascular response.

Abstract: Forty-one young male subjects performed either an easy or moderately difficult arithmetic task with the opportunity to earn a monetary incentive if they did well. Cardiovascular (heart rate, systolic and diastolic blood pressure) and subjective responses were assessed immediately prior to and 5 min following task performance. Results indicated greater systolic (SBP) responses during the Pre-task period for subjects expecting to perform the difficult task. Behavior pattern classifications based on the Jenkins Activity Survey revealed Higher Pre-task heart rate (HR) elevations among Type As compared to Bs in the Difficult task condition, and greater Pre-task SBP responses in As compared to Bs irrespective of task difficulty. There also was some evidence of an association between SBP reactivity and scores on the Thurstone Activity scale. Change-scores reflecting SBP and HR reactivity were correlated in the Pre-task period of the Difficult but not the Easy condition. Predictions regarding the impact of motivational arousal upon goal attractiveness were not supported, possibly for methodological reasons.

The relationship between arterial blood pressure and pulse transit time during dynamic and static exercise.

Abstract: The relationships between arterial systolic and diastolic blood pressure (SBP and DBP), interbeat interval (IBI), and various pulse transit times were investigated in 5 young, healthy males during physical exercise and at rest. Transit times monitored were radial, brachial and dorsalis pedis RPIs (ECG R-wave to pulse intervals), and brachial-radial and radial-dorsalis pedis PPIs (pulse to pulse intervals). Experimental sessions consisted of three periods: two involving mild dynamic exercise plus rests, and one involving static exercise (handgrips) plus rests. Correlation and regression analyses within period and subject were performed on individual beat data. Radial RPI was highly correlated with SBP (during dynamic periods, range −.57 to −.89, median r−.81; during static periods, range −.80 to −.88, median r=−.87) and moderately correlated with DBP (during dynamic periods, range −.10 to −.63, median r−.52; during static periods, range −.17 to −.77, median r−.66). Median correlations of radial RPI with SBP and DBP during exercise and rest separately were −.75 and −.40 (dynamic), −.79 and −.57 (static), and −.74 and −.26 (rest). The IBI X radial RPI product was very highly correlated with the rate-pressure product (heart rate X SBP), an index of myocardial oxygen consumption (median r=−.96). The only PPI which reliably indexed SBP or DBP change was brachial-radial PPI during the static exercise period (median r=−.86 and −.83).

Cardiovascular effects of mental arithmetic in Type A and Type B females.

Abstract: The cardiovascular responsivity of women demonstrating the Type A coronary-prone behavior pattern was investigated by presenting female Type A and Type B subjects with a challenging mental arithmetic task. Female subjects responded to the task with elevations in heart rate, blood pressure, and forearm blood flow, but did not show the active vasodilatation in the forearm vasculature seen in males in an earlier study. Type A females as a group were not hyperresponsive compared to Type B. However, measures of Type A behavior interacted with family history of hypertension such that, in the subgroup with a positive family history, the Type A behavior pattern was associated with larger cardiovascular responses. The results suggest that sex differences could be present in the expression of the cardiovascular concomitants of Type A behavior. Both gender and family history of cardiovascular disease may represent additional dimensions in the understanding of the pathological mechanisms linking Type A behavior and coronary disease.

Lucid, Prelucid, and Nonlucid Dreams Related to the Amount of EEG Alpha Activity during REM Sleep

Abstract: Alpha activity during REM sleep without signs of awakening can discriminate between the blind classification of prelucid, lucid, and nonlucid dreams. Ten good dream recallers were aroused after relatively high or low amplitude REM alpha. The spectral and temporal characteristics of EEG alpha within each REM period were associated with lucidity and other content dimensions. Each type of dream had a reasonably distinct pattern of REM alpha. High amplitude alpha was found to be associated with prelucid dreams and bizarre content, which is consistent with theories of waking alpha activity and the hypothesis that lucidity sometimes emerges from prelucid experiences. The data are also consistent with the idea that lucidity is a viable dream content dimension, and interpreted in terms of systems theory imply that training which emphasizes dream content control may constrain the potential information integration function of lucid dreams.

A reexamination of fear and its determinants on the visual cliff.

Abstract: Richards and Rader (1983) argue in their recent Psychophysiology paper that crawling experience plays no significant role in the development of visual cliff performance, and also that “fear” is not related to the development of the avoidance of heights. It is our contention that these conclusions rest upon oversimplified assumptions about the nature of fear and its determinants on the visual cliff. A very different set of inferences emerge from an alternative conceptualization of the problem. In contrast to Richards and Rader, we argue that heart rate cannot be simply equated with fear but rather represents one of many loosely correlated indices. Evidence is presented to show that behavioral and cardiac responses converge to demonstrate fear of heights by locomotor infants. It is further argued that the role of crawling experience is not given an adequate test by Richards and Rader. The theoretically important test involves a comparison between locomotor and prelocomotor infants. Data from such comparisons are reviewed and found to support self-produced locomotion as an important predictor of visual cliff performance.

Spontaneous vigilance fluctuations in the daytime.

Abstract: Spontaneous fluctuations of vigilance during the daytime were studied in 412 electroencephalographic (EEG) records from 9 subjects. The EEGs were recorded repeatedly 19–25 times between 0800 and 1900 in each subject. Except during the 5-min recording periods when seated subjects were examined with their eyes closed, the subjects were encouraged to engage in their normal daytime activities, such as reading and knitting. The changes in vigilance level were indicated by EEG measures based on automatic analysis. Statistical analyses of the data showed that vigilance fluctuations occurred rhythmically with a period between 60 and 110 min. The ultradian vigilance rhythms were detectable even though the subjects were engaged in normal daytime activity. Individual patterns of ultradian rhythms were, however, observed to be relatively unstable when within-subjects comparisons were made between experiments conducted one to six weeks apart.

Individual differences in the cardiac response to high intensity auditory stimulation

Abstract: A recently reported long latency cardiac acceleration to the initial presentation of a high intensity white noise stimulus was investigated further with pure tones. In three experiments (involving 128 subjects) marked individual differences in the secondary response were uncovered. Many subjects not showing acceleration exhibited a secondary deceleration. Subjects were categorised into Accelerators, Decelerators, and a non-consistent-change group on the basis of cardiac activity in a 17-50 s poststimulus epoch. While both Accelerators and Decelerators exhibited short latency cardiac acceleration, it was of greater magnitude in the former. The long latency response is discussed with reference to a distinction between the defensive reflex and the fight/flight response. Discussion of the short latency response focuses on the startle reflex and the‘What's-to-be-done?’component of the response to a novel stimulus.

Cerebral lateralization and heartbeat discrimination.

Abstract: This study examined individual differences in visceral perception as a function of cerebral lateral preference as assessed by conjugate lateral eye movements. Subjects were classified as “left movers” (i.e., right hemisphere preferent) or “right movers” (i.e., left hemisphere preferent). “Right movers” performed at chance level on a heartbeat detection task, whereas “left movers” performed significantly above chance. With knowledge-of-results (KOR) training all subjects showed a significant increment in performance, but the left movers maintained their superiority. These results support the hypothesis that performance on a visceral perception task may be subserved by relative activation of the right hemisphere.

Phasic T-wave amplitude and heart rate changes as indices of mental effort and task incentive.

Abstract: The sensitivities of T-wave amplitude (TWA) and heart rate (HR) to manipulations of the mental effort (ME) and incentive associated with performance of the backward digit span task were investigated. The experimental task was so chosen because it could be administered without requiring subjects to speak during its performance, thus minimizing the intrusion of respiratory and motor artifacts. The ME required during task performance was manipulated by varying the number of digits presented, creating Hard and Easy trials. The incentive for subjects to perform well was varied by the threat of the delivery of a noxious noise stimulus, which was ostensibly contingent upon adequate performance on some (Test) but not other (Practice) trials. TWA attenuation and HR acceleration were greater on the Hard as compared to the Easy Trials, and on the Test as compared to the Practice trials. No interactions between the ME and Incentive factors emerged for either cardiac variable. These results suggest that the effort and the incentive of subjects during mental work may be indexed reliably by phasic changes in TWA and HR. The conjoint use of these two cardiac measures may also elucidate the involvement of the two autonomic branches during task performance.

Alcohol and the Psychophysiological Detection of Deception

Abstract: Psychophysiological detection of deception examinations were conducted on 40 subjects. Of these, 32 were “guilty” of a mock crime and 8 were innocent. Sixteen guilty subjects committed the crime while intoxicated and the remaining 16 committed the crime sober. These two groups of guilty subjects were subdivided such that half of each group was examined with the polygraph while intoxicated and the other half was examined while sober. Two questioning techniques were used in the examination, a Control Question Test and the Guilty Knowledge Test. Measures of skin resistance, heart rate and respiration were recorded. The principal findings were that alcohol intoxication during the crime reduced detectability with detection scores derived from the measurement of skin resistance responses on the Control Question Test and on the Guilty Knowledge Test. The analyses of guilt/innocent classifications, based on the detection scores, showed these classifications to be affected by alcohol intoxication.