A computer-based, quantitative technique for assessing degree of regulation of EEG rhythms.

A quantitative method of assessing the degree of regulation of EEG rhythms is described. The method requires the measurement of the durations of a large number of waves in a person's EEG; these measures are then cast into a frequency distribution. Analysis involves the computation of the first four central moments of the frequency distributions. The procedure normally is carried out on a computer, but alternatively it can be done manually as well. Data reported on 126 children, aged 4-17 years, suggested that the method provides a quick and easy way of measuring regulation of the EEG rhythms. Substantial, statistically significant correlations between age and the 2nd, 3rd and 4th central moments revealed that regulation is relatively poor in young children but improves progressively over the age span investigated. In a group of 12 adults that were also studied, the magnitudes of the 2nd, 3rd and 4th central moments were significantly associated with a clinical electroencephalographer's judgment of the degree of dysrhythmia shown in their EEG tracings. Findings suggest that the method may provide an objective, quantitative means of assessing EEG dysrhythmia.

Time perception in relation to pulse rate in healthy males.

Time estimation by the production method and pulse rate under resting but attentive conditions were investigated in 92 healthy males. Subjects estimated intervals of 30, 60, and 180 sec following which they participated in an hour-long watchkeeping task during which pulse rate was recorded. Both the time estimates and pulse rate in the group covered a wide range of values. Correlations between pulse rate and time estimates in the group were all negative; the largest and only statistically significant correlation was equal to -.205. It was concluded that pulse rate plays only a minor if not insignificant role in the perception of time.

Ear asymmetry in telephone-listening behavior.

The notion that the right ear has an advantage over the left ear in verbal information processing was investigated. Telephone-listening behavior was surveyed in three different groups of subjects to discover whether there is a preference for listening with the right ear. Subjects included 97 persons selected at random whose jobs involved heavy use of the telephone, 141 persons also selected at random whose jobs did not involve heavy use of the telephone, and 99 university secretaries. It was anticipated (1) that a right-ear advantage would be present in all three groups, (2) that the right-ear advantage would be more prominent in persons who used the telephone a great deal, and (3) that the right-ear advantage would be most pronounced in secretaries since they frequently work in noisy offices where competition occurs between the auditory pathways. Findings showed no evidence of a right-ear preference either at the time the survey was conducted or in the respondents' report of their usual telephone-listening behavior. Instead, a statistically significant left-ear preference was discovered in all three groups. Always listening with the left ear was associated with heavy use of the telephone. The most frequently given reason for listening with the left ear was that it freed the right hand for writing and dialing. This preference would appear to be motivated by convenience for although either ear is available for listening, it is easier to hold the receiver to the left than the right ear while grasping it in the left hand. Findings cast doubt on the view that the right ear has an advantage over the left ear in verbal information processing.

Cortical evoked potentials in Gilles de la Tourette's syndrome--a single case study.

Average cortical evoked potentials (AEPs) to auditory stimulation and AEP recovery functions were investigated in a 13-year-old boy suffering from Gilles de la Tourette's syndrome. Data obtained from the patient while on and off haloperidol were compared with data from a group of normal control subjects matched for age and sex. Latencies of the P2 and N2 components of the AEP were noticeably shorter in the Tourette's syndrome patient than in the control group. Recovery from stimulation, as estimated by the cortical evoked potential to the second of two closely spaced stimuli, was faster in the patient than the controls. After the patient's treatment with haloperidol, the latencies of the P2 and N2 components of the AEP and the speed of recovery from stimulation appeared to be no different in the patient than in the control subjects. Findings suggested that cortical excitability is higher in the Tourette's syndrome patient, whose AEPs also showed evidence of a maturational advance over the normal subjects.

Recovery of the cortical evoked potential from auditory stimulation in children and adults.

The recovery of cortical evoked potentials to auditory stimulation was studied in a group of 12 young adults and 12 children aged 9.0-13.3 years. Subjects listened to single clicks and to pairs of clicks in which the interstimulus intervals (ISI's) varied, taking on values of 50, 100, 250, 500, 750, and 1000 msec. Average evoked potentials (AEP's) based on 50 repetitions were obtained to single clicks by coherent averaging and to the 2nd click of the pairs by automatically subtracting the evoked potential to each single click from the evoked potential to the corresponding pair and coherently averaging the remainder. In children, peak latencies of the P1, N1, and P2 components of the AEP to the 2nd click of the pairs increased significantly with decreasing ISI; in adults, latencies similarly increased except in the case of the N1 component. These increases were significantly larger in children than in adults, indicating that cortical recovery is slower in children and suggesting that cortical excitability in children may be lower. Peak latencies of the P1, N1, and P2 components of the AEP to single clicks were significantly lower (16-21 msec) in the children.

Cortical evoked potentials in monozygotic twins and unrelated subjects: comparisons of exogenous and endogenous components.

Cortical evoked potentials to auditory stimulation were recorded in six pairs of monozygotic twins and six pairs of unrelated subjects matched for age and sex while they performed a stimulus detection task. The cortical potentials were coherently averaged, and the peak latencies of the exogenous (P1, N1, and P2) and endogenous (N2 and P3) components of the average evoked potential (AEP) were investigated. It was hypothesized that latency of the exogenous components of the AEP would be similar in all matched pairs since the characteristics of these components depend primarily on the physical parameters of the stimulus. As endogenous components appear to be associated with a person's intentions, expectations, and decisions, we expected them to be more alike in twins than in unrelated individuals. Findings were in accord with the hypothesis. Latencies of the exogenous components were closely similar in all pairs of subjects. By contrast, latencies of the endogenous components were significantly (P less than or equal to 0.001) more alike in twins than in unrelated subjects.

Gilles de la Tourette syndrome: a 20-month study of the effects of stressful life events and haloperidol on symptom frequency.

The frequency of tics in a 10-year-old boy suffering from Gilles de la Tourette syndrome was investigated in the laboratory and at home using counts of tics made by the parents. The study spanned 20 months during which time the patient was treated with haloperidol. Parents' counts were reliable and valid. Stressful life events overcame positive medication effects, and symptom level varied markedly with the activities in which the child engaged. Such situational variability may explain the previously reported waxing and waning of symptoms. Findings also suggested that specific counseling be given when haloperidol is prescribed in order to prepare parents and patients for any apparent worsening of the disorder that may actually be due to the presence of stressful life events.

The electroencephalogram in a case of pituitary dwarfism before and after eight years of treatment with human growth hormone.

The EEG of an 11-year-old hypopituitary dwarf was investigated to determine whether the disorder was accompanied by a disturbance in cortical maturation. By means of a previously derived equation relating age and the first four central moments of the EEG interval histogram in normal children, the dwarf's developmental age was estimated from his EEG to be only about 6 1/2 years. After 8 years of treatment with human growth hormone, age estimated from the EEG was 8 2/3 years - an increase of barely more than 2 years.

Changes in the electroencephalogram accompanying the use of stimulant drugs (methylphenidate and dextroamphetamine) in hyperactive children.

Fifteen hyperactive boys aged 5.6-10.6 years had their electroencephalograms (EEG) recorded during performance of a simple reaction task while on stimulant medication (methylphenidate or d-amphetamine) and after being free of medication for at least 48 hr. Interval histograms were formed from measurements of the duration of 780 half waves taken from predetermined portions of the EEG'S recorded from the left parietal-occipital derivation for both treatment conditions, and the histograms were subjected to a central-moments analysis. Previous evidence showed that, in normal children, smaller-valued 2nd, 3rd, and 4th central moments were associated with greater maturity. The EEG histograms obtained while the hyperactive children were taking stimulant medication had significantly (p less than 0.005) smaller 2nd, 3rd, and 4th central moments than the histograms of the same children obtained when off medication. Age of the group predicted from the means of the 2nd, 3rd, and 4th central moments of the EEG interval histograms was 91 months when the children were off medication--9 months less than the group's actual mean age. Age predicted in the same way when the children were on medication was 97 months. Findings support the concept of a neurophysiological maturational lag in hyperactivity and suggest that this lag is overcome, in part, by the use of stimulant drugs.

Interval histograms of period of the electroencephalogram and the reaction time in twins.

Measures of central tendency, dispersion, skewness, and kurtosis of interval histograms of half wavelengths in the electroencephalogram (EEF) and performance on an auditory reaction time (RT) task were compared in seven pairs of male monozygotic twins aged 101-134 months and seven pairs of unrelated boys matched to the twins for age. Interval histograms were formed from measurements of 780 half waves taken from EEGs recorded from the left parietal-occipital derivation while subjects performed the RT task. Except in the case of the dispersion of the EEG distributions,the F ratios of within-pair variance in unrelated pairs to within-pair variance in twins were all statistically significant at the 0.05 level of confidence. Statistically significant intraclass correlations of means, medians, and modes of the histograms were found in the group of monozygotic twins but not in the sample of unrelated subjects. Intraclass correlations for dispersion, skewness, and kurtosis of the histograms and for RT were not significantly different from zero in either the twins or unrelated subjects. EEG findings suggested that the basic frequency of the brain's rhythmic electrical activity may be genetically determined; RT findings were inconclusive.

Reaction time and the psychological refractory period in children and adults.

The psychological refractory period-the prolonged reaction time (RT) to the second of 2 closely-spaced stimuli-was investigated in groups of 13 children and 13 adults. Subjects responded as fast as possible to the 2nd of 2 loud clicks that were presented after a soft click which served as a ready signal. The inter-stimulus interval (ISI), or time between loud clicks, was investigated as an independent variable. The results for ISI's of 50, 100, 250, and 500 msec confirmed the existence of an inverse relationship between RT and ISI. In accordance with the hypothesis investigated, RT was more prolonged in children than in adults as ISI decreased. Findings were consistent with the view that refractory period (RP) of an information-processing element in the central processor is longer in children than in adults. A single-channel model of information processing was proposed which could explain the inverse relationship between RT and ISI; could account for the slope differences between the RT vs ISI curves from children and adults; and could account, in part, for the overall longer RT's of children than of adults.

Heart-rate effects on human reaction time.

Intra-subject rs between auditory RT and heart rate for 100 males (Mage = 55 yr.) showed RT to be independent of heart rate determined from single bears. rs were of negligible magnitude though more than a chance number were significant.

Reaction-time variability, periodicities in reaction-time distributions, and the EEG gating-signal hypothesis.

Variability in a person's reaction time (RT) was investigated in relation to a model which hypothesized that the speed of information processing is a function of two factors, namely, the time characteristics of a cortical gating signal, and the recovery period of the events activated by the gating signals. A total of 280 RTs were obtained from each of six young adult subjects while electroencephalograms (EEGs) were simultaneously recorded. Half of the trials were performed under conditions which yielded short, low variability RTs while the other 140 trials were obtained under conditions which produced longer, highly variable RTs. Distributions of RTs from the two conditions were examined in relation to distributions of EEG half waves - which were assumed to define the period of the cortical gating signal - taken from the interval between stimulus and response. Findings were consistent with the model under investigation, namely: (1) the two different conditions produced periodicities or multiple peaks in the RT distributions; (2) the magnitude of the time intervals between consecutive peaks in the subjects' RT distributions was correlated with the duration of the most frequently occurring half waves in their EEGs; and (3) inter-subject differences in variability of the RT distributions were associated with differences in variability of the EEG distributions.

The electroencephalogram in the prediction of human reaction time during growth and development.

Characteristics of the distributions of electroencephalographic (EEG) half waves recorded in children during performance of a simple auditory reaction time (RT) task were investigated. The purpose was to determine the extent to which difference in these distributions could account for children's slow RT. The durations of a sample of 760 EEG half waves in each of a group of 41 healthy children aged 5-17 yr were measured and distributed into an interval histogram, and the first four central moments of the 41 distributions were computed. All four of the moments-which measure the central tendency, dispersion, skewness and kurtosis of the distributions-proved to be significantly correlated (p less than 0.01) with RT. The multiple correlation (R) between RT and the four moments was equal to 0.68 and was statistically significant. R was unchanged when only the measures of dispersion, skewness and kurtosis were used as predictor variables, suggesting that the predictive value of the central tendency is low. The predictive capability of a multiple regression equation based on these three predictor variables was tested in an independent group of 42 children also aged 5-17 yr. EEGs and RTs were recorded and this group was treated in exactly the same way as the other group. The correlation between these children's average RTs and their RTs as estimated from the other group's regression equation was 0.53. These findings suggested that knowing the degree of dispersion, skewness and kurtosis of the children's EEG distributions reduces from chance by about 28% the error of predicting their RTs.