Activity status in psychophysiologic studies. "Changes in the general activity level in psychophysiologic studies--an analysis of objective and subjective parameters"

The general activation level (GAL) is one of the sources of influence in psychophysiological experiments. That means most of the results are dependent on the GAL. Taken this into account one can furthermore elucidate a part of the high variability of the interesting physiological data. We analysed heart rate (HR), auditory evoked potentials (AEP) elicited by background stimuli and the subjective assessment of the internal state of the subjects to describe changes of the GAL. Summarizing the results we can show different influences of the GAL on the physiological data. Changes of HR and AEP-parameters are caused by specific experimental conditions. The distinct influence of the subjective state of the subjects on the AEP-shapes allows the conclusion that subjective data should be more taken into consideration. The comprehensive characterization of the GAL requires data of different integrative levels.     

Note on relation of autonomic perception to voluntary control of heart rate.

Relationships between subscores of the Autonomic Perception Questionnaire and ability to raise and lower heart rate voluntarily were examined in 40 subjects. Subscores which reflected autonomic awareness in anxiety and pleasure states were not predictive of degree of cardiac control, while the subscore specific to reported awareness of heart functioning during pleasure states only was positively correlated with ability to raise heart rate.     

Hemispheric asymmetry of auditory evoked potentials to comparisons within and across phonetic categories

In 10 right-handed Ss, auditory evoked responses (AERs) were recorded from left and right temporal and parietal scalp regions during simple discrimination responses to binaurally presented pairs of synthetic speech sounds ranging perceptually from /ba/ to /da/. A late positive component (P3) in the AER was found to reflect the categorical or phonetic analysis of the stop consonants, with only left scalp sites averaging significantly different responses between acoustic and phonetic comparisons. The result is interpreted as evidence of hemispheric differences in the processing of speech in respect of the level of processing accessed by the particular information processing task.     

Contrast effects on the auditory evoked response and its relation to psychophysical judgments

An auditory average evoked response (AER) procedure was used to search for a physiological counterpart of the contrast effect-the tendency for a S’s judgment of the intensity of a stimulus to be modified by the intensity of prior stimulation. When a tone was preceded by a softer tone, its AER amplitude increased; conversely, when a tone followed a louder tone, amplitude decreased. Irregular intervals between tones decreased the AER contrast effect, as did increasing the interval between tones. Further, significant correlations were found between individual scores on the AER contrast procedure and performance on a battery of psychophysical tasks.     

Stimulus control of heart rate by auditory frequency and auditory pattern in pigeons

A new method was used to investigate auditory discrimination in pigeons. Basically, the method involves the repeated presentation of one stimulus preceding the single presentation of a different stimulus that is followed by shock. Stimulus control is assessed by the increase in heart rate that accompanies the presentation of the second stimulus. In Experiment 1, the efficiency of the method was explored by determining the frequency difference thresholds of pigeons at 500, 1000, 2000, and 4000 Hz. Weber fractions comparable to those reported in an earlier study using the conditioned suppression method were obtained. Experiment 2 demonstrated that, contrary to results of earlier studies, auditory temporal patterns can exercise differential stimulus control in pigeons. One stimulus consisted of the presentation (once per second) of a 1000-Hz pure tone of 150 msec duration followed by a 2000-Hz pure tone of equal duration; the other was the same except for the reversed order of the frequency components. Results indicated that the frequency pattern and not the loudness pattern of the stimuli was the cue controlling heart-rate changes.     

The effect of smoking on brainstem auditory evoked potentials in positive- and negative-symptom schizophrenia

Studying brainstem auditory evoked potentials (BAEPs) and comparing the specific waves in smokers vs nonsmokers in both positive- and negative-symptom schizophrenia may elucidate the role of smoking in information processing. BAEPs were recorded in 40 patients with schizophrenia; 20 had predominantly positive symptoms (10 smokers and 10 nonsmokers) and 20 had predominantly negative symptoms (10 smokers and 10 nonsmokers). The severity of positive and negative symptoms was assessed by scale of assessment of positive symptoms and scale of assessment of negative symptoms (SANS). The BAEP results were compared with 15 healthy control individuals matched with the patients by age, sex, and cultural background. The smokers with negative symptoms showed a significant increase in the alogia, summary, and composite scores of SANS as compared to the nonsmokers. Although, most of the BAEP abnormalities were among patients with positive symptoms. The effect of smoking on the BAEPs was only in patients with negative symptoms. We also studied the interaction between smoking factor (smokers vs nonsmokers) and group type (group with mostly positive symptoms vs group with mostly negative symptoms) on the BAEPs and found a significant difference only for the first-wave latency mainly on the right side (P=0.012). The absence of a significant effect of smoking on most of the parameters of the BAEPs on interaction with the group factor suggests that the effect of smoking on the BAEPs is more apparent when negative symptoms prevail. However, studies are warranted to substantiate this finding.     

The psychophysiology of the visual thought perception of visually evoked brain potentials and recognition mechanisms

The study tries to demonstrate, that the combination of the actualgenetic method (Sander, Froehlich), and the VEP, allows a systematic and differentiated analysis of the psychophysiological process of visual thinking. A student group was compared with mental retardates in VEP and EOG, watching actualgenetically manipulated picture series. Phasic EEG-changes are significantly related to the identification process. Most sensitive are amplitude changes about 120 to 270 msec. The mental retardates had significant VEP changes 180--270 msec, the students 128--192 msec after picture presentation. The process factor analysis (Pawlik) elaborated an illumination factor and two factors being labelled general reaction set. VEP averaging over the persons revealed different attention and/or discrimination behavior for the student group and the mental retardates, identifying the picture objects.     

Recovery cycle of the evoked heart rate response in sleeping humans

Paired auditory stimuli, presented during sleep, evoked biphasic heart rate responses of greater than 10-second duration. The magnitude of the response to a second stimulus varies with the time between stimuli. The recovery cycle for human subjects exhibits a subnormal period for both HR peak and trough components at 5-or 6-second interstimulus intervals, and a supernormal period for the HR peak at 9-or 10-second interstimulus intervals. Thus, subnormal and supernormal periods coincide with the peak and trough, respectively, of the biphasic evoked heart rate response.     

Changes in spontaneous slow potentials and visually (flash) evoked potentials in response to stimuli with no performance implication]

The influence of spontaneous slow potential shifts (SPSs) on visual (flash-)evoked potentials (VEPs) was studied. Eighteen subjects received 100 flashes. The sequence of interstimulus-intervals (ISIs) was pseudo-randomized. ISI-durations were 3, 5, 7, 9 or 11 seconds. EEG was recorded from Fz, Cz, Pz and Oz with linked-mastoids as reference. EEG was EOG-corrected and VEPs were calculated for preceding positive SPSs. Averaging was done for local SPSs; VEP pairings as well as VEPs were calculated over occipital SPS-polarities. Results showed an influence of SPSs on VEP-amplitudes. Differences in amplitudes were interpreted with the 'activation-correction'-hypothesis and with the 'ceiling'-hypothesis. Negative SPSs were followed by smaller negative peaks, and positive SPSs were followed by smaller positive peak-amplitudes. Differences in latencies of N145-P300 peak-to-peak amplitudes after SPSs of different polarity were explained with the threshold-regulation hypothesis. Spectral-analysis were done for SPS-data. There were only poor effects, showing increased parietal alpha 2-power after negative SPSs.     

Changes in perceived contrast,reaction time,and pattern-specific evoked potentials due to stimulus duration

Using patterned stimulation without luminance change, the authors manipulated the stimulus duration and measured three variables: the magnitude of contrast experience, simple reaction time, and the amplitude of pattern-specific visual evoked potentials. While contrast experience, measured by the scaling method, indicated no saturation below 85 msec, the other two variables saturated below 40 msec. The lower saturation value of the pattern-specific evoked potential is considered as the limit of the correlation between psychophysical measures and brain electric activity. This suprathreshold divergence can be seen as evidence that processes underlying the pattern-specific visual evoked potential components cannot be considered as mechanisms mediating subjective experience of spatial contrast.     

Concomitant short-term changes in the auditory evoked response, the EEG, and reaction-time performance in relation to the temporal parameters of stimulation

Abstract.— Two experiments are described in which short-term "habituation" of the auditory evoked response (AER) was examined using discrete trains of click stimuli and averaging across trains. In the first study, the stimuli consisted of randomly interspersed trains of regular clicks, at 3 or 10 sec interstimulus interval (ISI). In the second study, the ISIs were also short or long but were irregular varying between 2.4 and 3.6 sec in the former case and 6 to 12 sec in the latter. The N₁-P₂ component of the AER diminished within the 3 sec trains especially for the regular stimulation; no such development occurred with the longer ISI. The total voltage in the background EEG and the reaction-times to the stimuli showed essentially similar changes. The possible mechanisms governing the response decrement are discussed and it is concluded that the data may be interpreted in terms of the Groves and Thompson dual-process theory of habituation.     

Infant temperament and the brainstem auditory evoked response in later childhood.

Brainstem auditory evoked responses (BAERs) were evaluated on 10-12-year-old children (N = 56) who had been classified as high or low reactive to unfamiliar stimuli at 4 months of age. BAER measurement was selected because high reactive infants tend to become inhibited or fearful young children, and adult introverts have a faster latency to wave V of the BAER than do extroverts. Children previously classified as high reactive at 4 months had larger wave V components than did low reactive children, a finding that possibly suggests greater excitability in projections to the inferior colliculus. The fact that a fundamental feature of brainstem activity differentiated preadolescent children belonging to two early temperamental groups supports the value of gathering physiological data in temperament research.     

The value of auditory evoked brain stem potentials in the diagnosis of circulatory disorders in the area of vertebrobasilar circulation

The acoustically-evoked brain-stem potential in patients with vertebrobasilar insufficiency has enjoyed a varied diagnostic evaluation in the literature. Our own examinations reveal an advantage in subdividing AEBP changes into normal and marginal, slight and pronounced, within a group of patients with blood supply disorders in the vertebrobasilar region. AEBP permits inferences to be made on the extent of the damage. However, one should be chary of referring AEBP change of vascular origin to any particular section on the basis of these deductions alone. Only the comprehensive consideration of clinical symptoms, AEBP findings, and neuroradiological examination leads to a valid opinion on extent and location.     

Hemispheric contributions to the integration of visual and auditory information in speech perception

Differential hemispheric contributions to the perceptual phenomenon known as theMcGurk effect were examined in normal subjects, I callosotomy patient, and 4 patients with intractable epilepsy. Twenty-five right-handed subjects were more likely to demonstrate an influence of a mouthed ward on identification of a dubbed acoustic word when the speaker’s fag vase lateralized to the LVF as compared with the RVF. In contrast, display of printed response alternatives in the RVF elicited a greater percentage of McGurk responses than display in the LVF. Visual field differences were absent in a group of 15 left-handed subjects. These results suggest that in right-handers, the two hemispheres may make distinct contributions to the McGurk effect. The callosotomy patient demonstrated reliable McGurk effects, but at a lower rate than the normal subjects and the epileptic control subjects. These data support the view that both the right and left hemisphere can make significant contributions to the McGurk effect.     

Time-shrinking: a discontinuity in the perception of auditory temporal patterns.

Recent research at our laboratories in the field of human auditory time perception revealed that the duration of short empty time intervals (less than approximately 200 msec) is considerably underestimated if they are immediately preceded by shorter time intervals. Within a certain range, the amount of subjective time shrinking is a monotonous function of the preceding time interval; the shorter it is, the more it shrinks its successor. In the present study, the preceding interval was kept constant at 50 msec, and the following interval, for which the duration had to be judged, varied from 40 to 280 msec. The results showed that at up to 100 msec, the perceived duration increased to a much lesser extent than did the objective duration. Beyond 120 msec, the perceived duration quickly increased and reached a veridical value at 160 msec. Such a sudden change of perceived duration in a temporal pattern in which the objective duration varies gradually indicates a typical example of categorical perception. We suggest that such a categorization of the time dimension might be a clue for processes of speech and music perception.