Multivariate analysis of EEG coherence: stability of the metric, individual differences in patterning and response to arousal

When coherence is computed among all pairs of a multichannel EEG, the resultant matrix can be de-structured with conventional multivariate analysis procedures to characterize the patterning of electrophysiologic information at each frequency band of the EEG across brain regions. Six right-handed young men had EEG data recorded from left and right frontal, temporal, parietal, and occipital locations during three visits to the laboratory at one week intervals. During each session, data were recorded during a relaxation period, an alert resting period, and as loud white noise was presented. Factor analysis of coherence matrices showed a model pattern of a large posterior factor and an anterior factor, both of which were right-lateralized, plus a residual factor that was most often left-lateralized. Four of the six men showed this pattern on each occasion, particularly for the delta and the theta bands. Two men showed variant patterns, which were also stable over time. A priori de-structuring of the matrix into partial multiple intrahemispheric and inter-hemispheric coherences also showed generally higher coherences on the right side, with the exception of left occipital inter-hemispheric values. Effects of arousal manipulations were not striking, but the factor patterns suggested increases in right hemisphere coherence for the alpha and beta bands during high arousal.     

Pulmonary changes induced by frontal EMG training

Earlier research suggested that the effects of facial muscle tension changes on other responses are not widespread but limited to a rather narrow set of pulmonary events. Further evidence in support of the specificity of the facial muscle-pulmonary relationship was provided in the present study by monitoring changes in several responses as a function of muscle tension training. Feedback training for increases and decreases in muscle tension at both facial and limb muscle sites was given to adult males. The effects of these manipulations on PEFR, RR, and HR were examined. Increases in facial muscle tension resulted in PEFR decreases whereas increases in limb muscle tension did not. Decreases in facial muscle tension were not observed as a function of training and no PEFR changes resulted from these conditions. Neither RR nor HR were related to the facial EMG changes observed during feedback training. These observations demonstrated the specificity inherent in the relationship between facial muscle tension and PEFR. and lent support to the hypothesis that these two responses are linked reflexively.     

EEG differences as a function of creativity, stage of the creative process, and effort to be original

Results of two experiments examining the relationship between creativity and EEG alpha wave presence are reported. In Experiment 1, it was found that more creative subjects exhibited higher alpha indices during an analogue of creative inspiration than during an analogue of creative elaboration. This pattern was not found in less creative subjects. In Experiment 2 a similar effect was found in a more controlled setting and shown to be specific to creative subjects when they are instructed to be original but not when they are given no such instructions. No consistent relationship between creativity and basal EEG alpha activity was found.     

Creativity and cortical activation during creative, intellectual and EEG feedback tasks.

Thirty-two male subjects were divided into four groups based on their performance on the remote associates test and alternate uses test, two measures of creativity. Right EEG alpha presence was monitored under basal conditions, while subjects took tests of creativity and intelligence, and while they attempted to enhance and suppress the amount of alpha in a feedback situation. High scorers on the alternate uses test operated at a high percentage of basal alpha during all tests while high scorers on the remote associates test showed differential amounts of alpha presence across tests, with the highest percentage of basal alpha during tests of creativity and the lowest percentage during an intellectual test. Both high creative groups tended to show increases in amount of alpha across trials when trying to suppress alpha as well as when trying to enhance it, but did not differ in overall control from the low creative groups.     

Efficacy of pattern feedback for the dissociation of heart rate and respiration rate

The present study assessed the efficacy of pattern feedback for producing integrative and dissociative patterns of heart rate (HR) and respiration rate (RR). 60 uninformed subjects were assigned to six groups in which beat-by-beat feedback was contingent upon production of a specific pattern of increased (↑), decreased (↓), or unchanged (=) HR and RR during 11 feedback trials. Concomitant changes in respiratory volume and general activity (GA) were also recorded. Groups given feedback for HR and RR changes in the same directions (HR↑RR↑ and HR↓RR↓) and for changes in opposite directions (HR↑RR↓ and HR↓RR↑) were generally unable to produce the respective patterns, indicating that pattern feedback does not enable subjects to produce a wide range of HR-RR patterns. However, evidence of dissociation of HR and RR was obtained in the HR↑RR= and HR↓RR= groups in which HR changed significantly in the appropriate directions without significant changes in RR. These results are not consistent with the view that RR changes are necessary for HR control, although significant concomitant changes in respiratory volume and GA indicated that HR control was non-specific relative to these variables.     

The impact of two different reinforcers on conditioned operant heart-rate acceleration and deceleration.

The effects of two types of reinforcers on operant heart-rate acceleration and deceleration conditioning were examined over a number of sessions. The initial use of monetary reinforcement facilitated discriminative pre-trial to trial heart-rate acceleration during sessions utilizing both monetary reinforcement and visual feedback. The initial use of visual feedback did not produce such discriminative control, but the subsequent use of monetary reinforcement resulted in increases in pre-trial and trial heart rate over sessions. No effects due to type of reinforcement were noted for heart-rate deceleration. Increases and decreases in cardiovascular functioning were imposed upon a background of increased skin responding. The cardiovascular responses that developed over sessions appeared to be relatively independent of changes in skin response.     

Behavioural and electrodermal measures of lateralization for music perception in musicians and nonmusicians

Two groups of students, musicians and nonmusicians were tested on a dichotic listening forced choice recognition task with concurrent recording of bilateral electrodermal activity. Stimuli were excerpts of Bach 4-part chorales; probes were the soprano, bass, harmony or the chorale excerpt, with or without changed notes. Laterality effects in recognition and the GSR were obtained only in musicians as a function of the complexity of the task. It was concluded that styles of information processing assumed by the hemispheres are the consequence of an interaction between the stimulus and the state of the organism at the moment, such that the direction of laterality can change within a subject performing the same task depending upon its perceptual demand.     

Heart-rate decelerative Pavlovian conditioning with tilt as UCS: towards behavioural control of cardiac dysfunction.

As part of a programme the ultimate goal of which is to teach behavioural control of stress-induced maladaptive cardiac accelerations through Pavlovian decelerative conditioning, this study was directed at examining the feasibility of using tilting of the body from a head-up to a head-down position as the unconditional stimulus (UCS) to elicit phasic cardiac deceleration as the unconditional response (UCR). Experiment I assessed the reflexive features of the cardiac response to 32 tilt UCS trials delivered at mean intervals of 75 sec. The results yielded a large-magnitude (over 30 BsPM) cardiac decelerative UCR with fast recruitment and complete resistance to habituation. Experiment II examined the feasibility of using the tilt UCS to demonstrate associative control over decelerative responding to a tone as the conditional stimulus (CS). Relative to a control 'backward' UCS-CS group with an interstimulus interval (ISI) of 14.5 sec, a 0.5 sec ISI CS-UCS experimental group demonstrated both orderly acquisition and extinction performance. The magnitude of the conditional deceleration of some 4 BsPM is greater than the extent of control generally achieved with biofeedback, but still constitutes a problem for theoretical accounts of classical conditioning framed in terms of stimulus substitution, and is still only of borderline clinical significance.     

Effects of warning-signal duration on the early and late components of the contingent negative variation.

Slow EEG potentials were recorded from three sites on the scalp (Fz, Cz and Pz) during a simple reaction time task in which the duration of the warning signal was either 0.5 or 2 sec. The duration of the foreperiod was held constant, and order of conditions was varied according to a latin square design. As predicted, the longer warning signal evoked increased amplitude of the early component of the contingent negative variation (CNV). These results confirm the interpretation of that wave as an orienting response. In contrast, the duration of the warning signal did not affect the second CNV component or reaction time latency. Additional dissociation between the two CNV components was evident in their distribution on the scalp. The early component was smallest at Pz, whereas the late component attained its lowest amplitude at Fz. Concurrently recorded palmar skin potentials exhibited different polarity and latency from the CNV.     

Reduction of epileptic seizures through EEG biofeedback training

Biofeedback training of the sensorimotor rhythm (SMR) was carried out in three male and three female adolescent epileptics and in two normal controls. The patients represented a cross-section of epilepsies including grand mal, myoclonic, afocal and psychomotor types. Three of the cases were mentally retarded. 12–14 Hz (SMR) activity was detected by a combination of sharp analog filtering and digital processing. The patients were provided with feed-back whenever they produced 0.5 sec of 12–14 Hz activity of a specified amplitude. Additional feedback was provided for epileptiform activity slow waves or movement. Furthermore, feedback for SMR production was inhibited by digital logic circuitry when movement, slow waves or spikes were present. Seizure reduction was obtained in five of the six epileptics. Several patients showed increased percentage of SMR when feedback was provided and varying degrees of normalization in their EEG as demonstrated by fast Fourier, crossed power spectral density and coherence analyses.     

Behavioral responsivity during recovery sleep

Previous research has shown that REM-deprived subjects are more likely than non-REM-deprived subjects to perform an operant response during subsequent REM sleep when punishment (full awakening) for failure to respond was used. The present study used the same punishment procedure while attempting to extend these findings to other sleep stages. Response latencies were compared for six subjects under each of two conditions: Normal sleep occurring from 2300 to 0700 and recovery sleep occurring from 0700 to 1300 after 24 hr of continuous wakefulness. Alpha activity, EMG increases, stage shifts, and body movements were assessed to determine the amount of arousal associated with behavioral responding under both conditions. In general, response latencies lengthened during recovery sleep indicating a diminished ability to respond while no differences in arousal were evident.     

The impact of warning signal intensity on reaction time and components of the contingent negative variation.

Slow EEG potentials were recorded during performance of a simple reaction task in which warning signal intensity was varied from trial to trial under foreperiod durations of 1, 3 and 8 sec. As shown by speed of reaction, the warning signal had an activating effect which increased with its intensity and decreased with foreperiod duration. This effect was related to the amplitude of a slow potential which appears in the EEG shortly after presentation of the warning signal. This potential is interpreted as a component of the orienting response regulating sensitivity to subsequent stimulation, so that reaction time is affected through change in the effective intensity of the imperative signal.     

Temporal consistency of individual differences in cardiac response to a video game

Three experiments are reported which examined the temporal stability of cardiac reactions to a video game of the 'space invaders' genre. Experiment 1 also addressed the matter of inter-task consistency; in addition to the video game, subjects were presented with an unsignalled reaction time task and led to believe that relatively quick reactions attracted financial reward, while slower ones brought either a burst of loud noise or withdrawal of money previously earned. Forty-two male subjects were tested on both tasks on two occasions, a week apart. Of the two tasks, the video game elicited the greater reactivity. In addition, individual variations in reactivity showed striking temporal stability for both tasks. However, inter-task consistency was much less marked; in fact, a significant inter-task correlation was obtained only on the first occasion of testing. It is probable that limited consistency here was in some measure due to the ineffectiveness of our reaction time task in eliciting substantial reactivity. Finally, reactivity was independent of baseline heart rate level. In experiment 2, three extreme high and three extreme low cardiac reactors were selected from an initial sample of 23 male subjects, on the basis of reactivity during an initial session with the video game, and subsequently studied during four further sessions. Once more, impressive stability of heart rate reactivity was apparent over sessions. In experiment 3, we examined the reliability of individual variations in cardiac reactivity in women and the issue of whether temporal stability is constrained by menstrual cycle effects. Twenty-four females were tested on the video game both preovulatory and postovulatory, with half being tested first during the preovulatory phase and half being tested first during the postovulatory phase. Again, the most striking finding was the marked stability of individual variations in cardiac reactivity over both time and menstrual cycle phase.     

Anticipatory HR deceleration as a function of perceived control and probability of aversive loud noise: A deployment of attention account

Five groups of 10 undergraduate subjects each participated in an experiment to examine the effects of perceived control over, and the probability of occurrence of, noxious (white-noise) stimulation on anticipatory heart rate (HR) deceleration. All groups performed an arithmetic task, the numbers for which were changed on each of the 20 trials, but three groups were defined as active groups since they were instructed that the occurrence of noxious stimulation was contingent upon their performance on the task. The actual probability of occurrence of noxious stimulation (i.e., either 0.9, 0.5 or 0.1) was manipulated between these three groups. A fourth (passive) group (0.5 probability of occurrence) was instructed as to the non-contingent relationship between performance and the aversive white noise. The last group was a control group which only performed the task, and thus both provided an estimate of the rate of return to baseline following the expected HR acceleration to the task and eliminated the need for a within-subject control period to assess HR deceleration. The results indicated that all active and passive groups produced significant HR decelerations, relative to the control group, prior to the noxious stimulus. However, all active groups (regardless of probability levels) displayed significantly greater, and required more trials to maximally develop, anticipatory deceleration than the passive group. In addition, the results for the active groups revealed a direct relationship between the probability of occurrence of noxious stimulation and the magnitude of anticipatory deceleration. It is argued that the results cannot be adequately accommodated by the preparatory-adaptive-response theory. A deployment-of-attention account is suggested since it appears both to account for the obtained pattern of results completely and to generate additional testable predictions for the future.     

Stimulus omission and recovery of the electrodermal and digital vasoconstrictive components of the orienting response.

Three experiments are reported which investigated Sokolov's (1968) hypothesis that, after a number of stimulus presentations, complete omission of a stimulus leads to increased responsiveness of the orienting response (OR). The skin conductance response (SCR) and finger pulse volume (FPV) response components of the OR were studied. In experiment 1 (N=60), the effect of number of pre-omission training trials on response recovery was investigated, while experiment 2 (N=120) investigated the effects of stimulus intensity (70 or 90 dB) and interstimulus interval (12 or 21 sec) on recovery to stimulus omission following a fixed number of training trials. In experiment 3 (N=40), an attempt was made to control for possible below-zero habituation effects by training each subject to a habituation criterion before stimulus omission. All experiments employed a 1000 Hz tone of 3 sec duration which was presented at a constant interstimulus interval. Although recovery of the SCR did occur under some conditions, the results were largely negative. Manipulation of the number of training trials, training stimulus intensity and interstimulus interval had little effect on response recovery. A consistent finding, however, was that subjects who displayed SCR recovery also displayed significantly more spontaneous fluctuations in skin conductance during the pre-stimulus period and required significantly more training trials to reach the criterion of habituation than did subjects displaying no recovery. Moreover, the SCRs displayed by 'labile' subjects on omission trials were significantly larger than those displayed on either the last training trial or during a control interval just prior to stimulus omission.     

Anticipatory cardiac deceleration prior to total body movement in grade school children

A total of 16 males (mean age = 10.9 years) were tested on six trials of a signaled, running time task while heart rate was recorded. The preparatory interval varied randomly among 10, 15, or 20 sec. The response consisted of running a distance of 4.62 m. A triphasic heart rate response (deceleration-acceleration-deceleration) occurred following the warning signal. A stable deceleration below pre-stimulus levels was observed during the 5-sec period prior to the respond signal. Heart rate responses were not related to running time.     

Classical conditioning of autonomic responses in alert and drowsy subjects.

The primary purpose of this experiment was to study classically conditioned autonomic responses of alert versus drowsy subjects. Sixty-nine subjects in conditioning and pseudoconditioning groups were subdivided into alert and drowsy groups on the basis of EEG recordings during conditioning trials, giving a total of four groups: conditioning-alert, conditioning-drowsy, pseudoconditioning-alert and pseudoconditioning-drowsy. Using the latency criterion to define responses, significant conditioning occurred only in the conditioning-alert group for the following measures: skin resistance anticipatory and UCS-omission responses, and finger plethysmograph anticipatory response. Both conditioning groups showed evidence of conditioned UCS-omission plethysmograph responses. Discussion centered primarily on (1) the implications of the results on the question of the feasibility of learning during sleep; and (2) the importance of including EEG recordings in studies of classically conditioned autonomic responses. The relationship between the various responses was also evaluated.     

Effects of threat of shock and control over shock on finger pulse volume, pulse rate and systolic blood pressure

Previous research has evaluated finger pulse volume (FPV) as a psychophysiological measure and found it to reflect anxiety, orienting, effort and anger. Controllable versus uncontrollable threats have been found to have different effects on cardiovascular parameters, including pulse rate (PR) and systolic blood pressure (SBP). To date, no studies have compared the effects of such coping efforts on FPV with their effects on PR and SBP. The present study examined the response of PR, SBP and FPV to conditions of controllable shock, uncontrollable shock and no shock. As expected, SBP and PR measures were elevated in the controllable as compared to uncontrollable shock conditions, replicating previous work on cardiovascular responses to coping demands. In contrast, FPV was sensitive to the threat of shock, but did not differ as a function of the coping demands of the task. The findings were discussed in terms of the interpretation of FPV as a psychophysiological measure.