A quantitative EEG index of the orienting response in children

Attention and regulation of EEG alpha-attenuation responses

Two experiments with 16 normal adults of both sexes tested the hypothesis that inattention to a biofeedback display is associated with increased variability of those physiological processes that had been regulated by the biofeedback. Each experiment was a repeated-measures-on-independent-subjects-design. Dependent variables were the time durations and the mean rms power of two mutually exclusive segments of the parietal-occipital EEG: alpha and not-alpha segments. Independent variables were combination of counting tasks and instructions to look at, listen to, and count visual and auditory flashes and clicks. The durations of alpha and not-alpha segments were controlled or regulated by means of an alpha-contingent visual feedback stimulus, Attention to the feedback stimulus was challenged by instructions to count other, noncontingent stimuli. Control of alpha and not-alpha segments was least for conditions of (1) "sham" feedback, and (2) feedback with instructions to count noncontingent auditory clicks, which were presented 3/sec while the feedback visual stimuli were occurring. A new EEG test of attention and distraction was suggested.

Note on the EEG orienting response in children

Time durations of “alpha bursts” and of “alpha blocking” (no-alpha) intervals, which was the index of the orienting response, were measured by the EEG for 61 children, ages 5–6 and 9–10 yr. Three conditions were examined: (1) eyes closed in the dark (EC), (2) eyes open in the dark (EO), and (3) feedback visual stimulation (VS). Alpha durations were progressively briefer, while no-alpha durations were progressively longer, from EC to EO to VS. Older children had longer no-alpha durations. The differences among the three conditions were greater for older than for younger children with regard to no-alpha durations. The results suggest that the alpha-blocking response is changing between the ages of 5 and 10 yr.

Feedback control and quantification of the response of EEG alpha to visual stimulation

The response of the posterior EEG alpha thythms to visual stimulation is so variable that it is difficult to obtain reliable on-line measurement of it. Feedback between the EEG alpha and the visual stimulus (1) reduces random variation in the response and (2) facilitates on-line quantification. With feedback EEG, the response to visual stimulation is measured as a series of time durations of alpha and of no-alpha intervals in the EEG. This time series occurs in two stages: an initial disturbance followed by a recovery. The quantification of the series of time durations is achieved by fitting curves to the series of alpha time intervals and of no-alpha time intervals. These functions, computed in each trial of 30 stimulations, are an objective, quantitative definition of EEG response. The utility of the method was demonstrated by testing it with reference to well-known effects. Habituation to a repeated stimulus, dishabituation, habituation to a class of stimuli, dishabituation by changing the class of stimuli, and differences among brain-lesioned, psychiatric patients and normals were shown with a detailed quantification. It was concluded that biofeedback is the method of choice for quantitative research on the EEG component of the human orienting response.

Detection of EEG abnormalities with feedback stimulation

A feedback method for testing the reactivity of the occipital-parietal EEG in selected brain-lesioned patients revealed abnormalities of (a) insufficient reactivity, (b) bilateral differences in reactivity, and (3) asynchrony. These abnormalities were more evident during feedback stimulation than in the baseline conditions. The utility of feedback method for detecting EEG abnormalities rests on the increased stability or decreased "noisy" variation in the EEG during feedback. The EEG becomes more predictable even to the "on-line" human observer. This makes it easier to detect aberrations or deviations from normal effects. Some effects can only be seen with feedback such as the bilateral differences which occur when the left side controls the feedback compared to when the right side controls it. The results show that feedback EEG is a useful tool in clinical research and indicate that a clinical diagnostic test could be developed with more research. However, the feedback EEG method is not yet a proven diagnostic technique.

Hyperactive behavior and EEG arousal reactions in children

EEG arousal reactions and parameters of spontaneous EEG activity were studied in two extreme groups of behavior problem children (11 hyperactives and 11 non-hyperactives), selected on the basis of a rating of motor restlessness the core symptom of the "hyperactivity syndrome". The EEG was recorded in three reaction time experiments: a tone light conditioning paradigm and two series with random stimulation. An automatic analysis of EEG parameters was employed to describe the time functions of alpha amplitudes in the single trial. The main findings are: 1. In periods free from stimulation, hyperactive children have higher alpha and beta amplitudes, more alpha waves and a smaller amount of beta waves. This indicates a lower state of EEG arousal in the hyperactives. 2. The amplitude reduction to tone (in the single trial) develops more slowly in the hyperactive group. This group difference increases over the experimental situations. 3. The arousal responses to tone, in terms of the level of maximum amplitude reduction, become comparably weaker in the hyperactives across the experiments. 4. Under all experimental conditions the hyperactives exhibit shorter arousal responses to the light stimulus than the non-hyperactive children. 5. Reaction time performance of the groups is clearly different, hyperactives showing the longer latencies. 6. Although conditional changes in the arousal reactions to both stimuli are reliably demonstrable in all children, the groups show no difference in the corresponding measures. These findings are discussed under the aspects of activation and of attention behavior of the subjects.