RESUMO
OBJECTIVE: Examination of the EEG photic driving coherence during intermittent photic stimulation in autistic patients with relatively intact verbal and intellectual functions in order to enhance the likely latent interhemispheric asymmetry in neural connectivity. METHODS: Fourteen autistic boys, aged 6-14years, free of drug treatment, with I.Q. 91.4+/-22.8, and 19 normally developing boys were subject to stimulation of 12 fixed frequencies of 3-27Hz. The number of high coherent connections (HCC) (coherence >0.6-0.8) was estimated among 7 leads in each hemisphere. RESULTS: In contrast to the spectral characteristics showing the right hemisphere deficit in the photic driving reactivity, the number of HCC differentiated the groups only in the left hemisphere where it was higher in autistics at the EEG frequencies corresponding to those of stimulation at 6-27Hz without asymmetry at other frequencies, the left-side prevalence increasing with frequency. No asymmetry was observed in the resting state. CONCLUSIONS: Spectral and coherence characteristics of the EEG photic driving show different aspects of latent abnormal interhemispheric asymmetry in autistics: the right hemisphere "hyporeactivity" and potential "hyperconectivity" of likely compensatory nature in the left hemisphere. SIGNIFICANCE: The EEG photic driving can reveal functional topographic alterations not present in the spontaneous EEG.
Assuntos
Transtorno Autístico/diagnóstico , Transtorno Autístico/fisiopatologia , Córtex Cerebral/fisiopatologia , Eletroencefalografia/métodos , Lateralidade Funcional/fisiologia , Estimulação Luminosa/métodos , Adolescente , Fatores Etários , Envelhecimento/fisiologia , Córtex Cerebral/crescimento & desenvolvimento , Criança , Corpo Caloso/fisiologia , Dominância Cerebral/fisiologia , Potenciais Evocados Visuais/fisiologia , Humanos , Masculino , Valor Preditivo dos Testes , Tempo de Reação/fisiologiaRESUMO
The electroencephalogram amplitude spectra at 11 fixed frequencies of intermittent photic stimulation of 3 to 24 Hz were combined into driving "profiles" for 14 scalp points in 8 male and 7 female normal subjects aged 9 to 17 years. The driving response varied over frequency and was detected in 70 to 100% of cases in the occipital areas (maximum) and in 27 to 77% of cases in the frontal areas (minimum) using as a criterion peak amplitude 20% higher than those of the neighbors. Each subject responded, on average, to 9.7 +/- 1.15 intermittent photic stimulation frequencies in the right occipital area and to 6.8 +/- 1.97 frequencies in the right frontal area. Most of the driving responses (in relation to the previous background) were significant according to the spectral F-test (alpha = 0.05), which also detected changes in some cases of low amplitude responses not revealed by the peak criterion. The profiles had two maxima in the alpha and theta bands in all leads. The latter was not present in the background spectra in the posterior areas and was less pronounced in the anterior ones. The weight of the profile theta maximum increased towards the frontal areas where the two maxima were similar, while the profile amplitudes decreased. The profiles repeated the shape of the background spectra, except for the theta band. The interhemispheric correlation between profiles was high. The theta driving detected in all areas recorded suggests a generalized influence of the theta generators in prepubertal and pubertal subjects.
Assuntos
Eletroencefalografia , Potenciais Evocados Visuais/fisiologia , Lobo Occipital/fisiologia , Estimulação Luminosa/métodos , Adolescente , Criança , Feminino , Lateralidade Funcional/fisiologia , Humanos , MasculinoRESUMO
The electroencephalogram amplitude spectra at 11 fixed frequencies of intermittent photic stimulation of 3 to 24 Hz were combined into driving "profiles" for 14 scalp points in 8 male and 7 female normal subjects aged 9 to 17 years. The driving response varied over frequency and was detected in 70 to 100 percent of cases in the occipital areas (maximum) and in 27 to 77 percent of cases in the frontal areas (minimum) using as a criterion peak amplitude 20 percent higher than those of the neighbors. Each subject responded, on average, to 9.7 ñ 1.15 intermittent photic stimulation frequencies in the right occipital area and to 6.8 ñ 1.97 frequencies in the right frontal area. Most of the driving responses (in relation to the previous background) were significant according to the spectral F-test (a = 0.05), which also detected changes in some cases of low amplitude responses not revealed by the peak criterion. The profiles had two maxima in the alpha and theta bands in all leads. The latter was not present in the background spectra in the posterior areas and was less pronounced in the anterior ones. The weight of the profile theta maximum increased towards the frontal areas where the two maxima were similar, while the profile amplitudes decreased. The profiles repeated the shape of the background spectra, except for the theta band. The interhemispheric correlation between profiles was high. The theta driving detected in all areas recorded suggests a generalized influence of the theta generators in prepubertal and pubertal subjects.
Assuntos
Humanos , Masculino , Feminino , Criança , Adolescente , Estimulação Luminosa , Eletroencefalografia , Potenciais Evocados Visuais , Lateralidade Funcional , Lobo OccipitalRESUMO
In order to identify latent bioelectrical oscillators, 15 normal subjects (aged 9-17 years, 8 males, 7 females) were subjected to intermittent photic stimulation. The EEG amplitude spectra corresponding to the 11 fixed frequencies of stimulation presented (3-24 Hz) were combined to form "profiles" of the driving reaction in the right occipital area. The driving response varied with frequency, and was demonstrable in 70-100 percent of cases (using as criterion peak amplitudes 20 percent larger than those of the neighbors). The strongest responses were observed at the frequency closest to the alpha peak of the resting EEG. A secondary profile maximum was in the theta band. In 10 subjects, this maximum exceeded half the alpha peak (with an average of 72.4 percent of the alpha peak), while in the resting spectra, theta amplitudes were much lower than the alpha maxima. This responsiveness in theta activity seems to be characteristic of prepubertal and pubertal subjects. The profiles and resting EEG spectra showed a highly significant Pearson's correlation, with the peak in the theta band of the profiles being the main difference observed between them. The correlation coefficient was significantly correlated with the ratio of the maxima in the theta and alpha bands (R = -0.77, P<0.001). The correlation coefficient between profile and resting spectrum may be a useful indicator in screening methods used to reveal latent cerebral oscillators. Profiles for the second and third harmonics were correlated with those of the first harmonic (fundamental frequency), when considering the corresponding EEG frequencies. Peak frequencies in all three profiles were close to those of the individual's background alpha rhythm, and peak amplitudes in higher harmonics were not much lower than those of the fundamental frequency (mean values of 84 and 63 percent, for second and third harmonics, respectively)
Assuntos
Humanos , Masculino , Feminino , Criança , Adolescente , Estimulação Luminosa , Descanso , Eletroencefalografia , Lobo OccipitalRESUMO
In order to identify latent bioelectrical oscillators, 15 normal subjects (aged 9-17 years, 8 males, 7 females) were subjected to intermittent photic stimulation. The EEG amplitude spectra corresponding to the 11 fixed frequencies of stimulation presented (3-24 Hz) were combined to form "profiles" of the driving reaction in the right occipital area. The driving response varied with frequency, and was demonstrable in 70-100% of cases (using as criterion peak amplitudes 20% larger than those of the neighbors). The strongest responses were observed at the frequency closest to the alpha peak of the resting EEG. A secondary profile maximum was in the theta band. In 10 subjects, this maximum exceeded half the alpha peak (with an average of 72.4% of the alpha peak), while in the resting spectra, theta amplitudes were much lower than the alpha maxima. This responsiveness in theta activity seems to be characteristic of prepubertal and pubertal subjects. The profiles and resting EEG spectra showed a highly significant Pearson's correlation, with the peak in the theta band of the profiles being the main difference observed between them. The correlation coefficient was significantly correlated with the ratio of the maxima in the theta and alpha bands (R = -0.77, P<0.001). The correlation coefficient between profile and resting spectrum may be a useful indicator in screening methods used to reveal latent cerebral oscillators. Profiles for the second and third harmonics were correlated with those of the first harmonic (fundamental frequency), when considering the corresponding EEG frequencies. Peak frequencies in all three profiles were close to those of the individual's background alpha rhythm, and peak amplitudes in higher harmonics were not much lower than those of the fundamental frequency (mean values of 84 and 63%, for second and third harmonics, respectively).
Assuntos
Eletroencefalografia/métodos , Lobo Occipital/fisiologia , Estimulação Luminosa/métodos , Descanso/fisiologia , Adolescente , Criança , Feminino , Humanos , MasculinoRESUMO
In 67 borderline psychiatric patients suffering from schizotypal/slowly developing schizophrenic disorders and 18 patients suffering from cyclothymia, the factor structure of the period (interval-amplitude) parameters of the EEG proved to be similar to that obtained in normal subjects during mental activity and reported in part I (Lazarev, Int. J. Psychophysiol., 28 (1998) 77-98). However, 51 patients with schizotypal disorders with a predominance of asthenic-like symptomatology, characterized by mild thought disorders with difficulty in focusing attention, were distinguished from normal subjects, cyclothymic patients and other patients of schizotypy without well-defined asthenic symptoms by significantly increased values of EEG Factor II which was positively related to the index-presence in epoch, frequency and regularity of low-amplitude beta-waves, and reduced values of an EEG Factor III which was positively correlated with mean alpha-period and theta-index. According to normative data (part I; Lazarev, Int. J. Psychophysiol., 28 (1998) 77-98), this probably reflects a neurodynamic imbalance between an excess of 'cortical excitation' (Factor II) and a deficit of 'active selective inhibition' (Factor III). This imbalance appears to be opposite to the changes in values of these factors found in normal subjects during focusing attention and motor automation, when compared with relaxed wakefulness. The functional properties of Factors II and III ascribed on the basis of psychological testing suggest that such an imbalance could reflect a predominance of successively organised associative mental processes over the selective inhibition of irrelevant associations. This could cause difficulties in voluntary attention, mental automation and in the performance of simultaneous mental operations. In most cases, there was no difference in Factor I which was positively related to the index, amplitude and regularity of alpha-activity and wave amplitudes in other bands, and negatively related to the indices and mean periods of delta- and theta-waves, the factor presumed to depict 'general activation'.