Thesis (B.A.(Hons.))--University of Adelaide, Dept. of Psychology, 1976.

Thesis (B.A. (Hons.))--University of Adelaide, Dept. of Psychology, 1976.

No description available.

Thesis (B.Sc. (Hons.)) -- from the Department of Psychology, University of Adelaide, 1977.

Thesis (B.A. Hons.))--University of Adelaide, Dept. of Psychology, 1975.

Note:

No description available.

This thesis addresses some theoretical issues generated by the results of recent analysis of EEG time series proving the brain dynamics are driven by abrupt changes making them depart from the ordinary Poisson condition. These changes are renewal, unpredictable and non-ergodic. We refer to them as crucial events. How is it possible that this form of randomness be compatible with the generation of waves, for instance alpha waves, whose observation seems to suggest the opposite view the brain is characterized by surprisingly extended coherence? To shed light into this apparently irretrievable contradiction we propose a model based on a generalized form of Langevin equation under the influence of a periodic stimulus. We assume that there exist two different forms of time, a subjective form compatible with Poisson statistical physical and an objective form that is accessible to experimental observation. The transition from the former to the latter form is determined by the brain dynamics interpreted as emerging from the cooperative interaction among many units that, in the absence of cooperation would generate Poisson fluctuations. We call natural time the brain internal time and we make the assumption that in the natural time representation the time evolution of the EEG variable y(t) is determined by a Langevin equation perturbed by a periodic process that in this time representation is hardly distinguishable from an erratic process. We show that the representation of this random process in the experimental time scale is characterized by a surprisingly extended coherence. We show that this model generates a sequence of damped oscillations with a time behavior that is remarkably similar to that derived from the analysis of real EEG's. The main result of this research work is that the existence of crucial events is not incompatible with the alpha wave coherence. In addition to this important result, we find another result that may help our group, or any other research group working on the analysis of brain's dynamics, to prove or to disprove the existence of crucial events. We study the diffusion process generated by fluctuations emerging from the same model after filtering out the alpha coherence, and we study the recursion to the origin. We study the survival probability of this process, namely the probability that up to a given time no re-crossing of the origin occurs. We find that this is an inverse power law with a power that depends on whether or not crucial events exist.

Este avaliou as características do EEG numa população de indivíduos nonagenários cognitivamente normais tanto através da analise visual como espectral. A amostra constituía de 42 sujeitos com idade que variava de 90 a101 anos (media de 92 DP 3,0 anos) clinica e cognitivamente saudáveis vivendo em seus lares e totalmente independentes oriundos do ambulatório do grupo de neurologia cognitiva do HC (acompanhantes) e da Casa Idoso. Eles foram submetidos a uma entrevista, exame neurológico, avaliação neuropsicológica e um EEG digital com programas capacitados a realizar analise espectral e de analise de coerência.Foi avaliado através da analise visual o PF (pico de freqüência) da banda alfa em áreas posteriores,a reatividade alfa a abertura ocular ,a presença de atividade lenta nas regiões temporais, a ocorrência de variantes benignas e de atividade epileptiforme espontânea. Através da analise espectral foi determinado o PF espectral da banda alfa nas regiões occipitais, e a coerência inter-hemisférica para a banda alfa entre os eletrodos P3P4 e O1O2. Os resultados deste estudo confirmam os vários trabalhos da literatura, que concluíram que em indivíduos idosos saudáveis a freqüência do ritmo alfa nas regiões posteriores do cérebro nunca foi menos que 8,0 Hz, e que as mulheres apresentam um pico de freqüência maior que os homens. A reatividade do ritmo alfa à abertura ocular foi observada em 41 sujeitos (97,61%) do total, e atividade lenta nas regiões temporais em 9 indivíduos (21,42%) com predomínio no hemisfério cerebral esquerdo. O valor médio para a coerência inter-hemisférica obtida para banda alfa em P3P4 e O1O2 foi respectivamente 0,61(DP 0,11) e 0,65( DP 0,13), e não foi detectado nenhuma diferença significa relacionada ao sexo, e nem uma redução deste valor com o envelhecimento. Conclusão: indivíduos idosos nonagenários cognitivamente normais apresentam um pico de freqüência para o ritmo alfa em áreas posteriores do encéfalo (eletrodos O1O2) igual ou maior que 8,0 Hz, e que valores abaixo desta faixa pode significar anormalidade e que as mulheres tem uma freqüência maior que os homens. A reatividade à abertura ocular do ritmo alfa permanece apesar da idade avançada e que sua ausência pode significar algum comprometimento funcional. A presença de alentecimento nas regiões temporais um achado que para muitos autores pode ser normal durante a senescência, foi observada neste estudo em somente 21% dos indivíduos, e não teve nenhuma correlação significativa com o perfil cognitivo e nem com o nível de escolaridade. A coerência para banda alfa em áreas posteriores (P3P4 e O1O2) não apresenta alteração importante durante o envelhecimento / This study evaluated the characteristics of the EEG in a population of cognitively normal nonagenarian individuals both through visual and spectral analysis.The sample consisted of 42 subjects ranging from 90 to 101 years (median of 92 years), clinically and cognitively healthy living in their homes and totally independent. In the outpatient clinic of the cognitive neurology group of the HC (companions) and of the Elderly House (Casa do Idoso). They were submitted to an interview, neurological examination, neuropsychological assessment and a digital EEG with programs capable of performing spectral analysis and coherence analysis. Through the spectral analysis it was evaluated the PF (peak frequency) of the alpha band in posterior areas, the alpha reactivity to ocular opening, the presence of slow activity in the temporal regions, the occurrence of benign variants and spontaneous epileptiform activity. Through the spectral analysis the spectral PF of the alpha band was determined in the occipital regions, and the interhemispheric coherence for the alpha band between the electrodes P3P4 and O1O2. The results of this study confirm a various studies in the literature, which concluded that in healthy elderly individuals the frequency of the alpha rhythm in the posterior regions of the brain was never less than 8.0 Hz, and that women presents a higher frequency peak than men. Reactivity of the alpha rhythm to ocular opening was observed in 41 subjects (97.61%) of the total, and slow activity in the temporal regions in 9 individuals (21.42%) with predominance in the left cerebral hemisphere. The mean value for the interhemispheric coherence obtained for the alpha band in P3P4 and O1O2 was 0.61 (SD 0.11) and 0.65 (SD 0.13), respectively, and no difference was detected related to sex, nor reduction of this value with aging. CONCLUSION: Cognitively normal nonagenarians (90 to 101 years of age) have a peak frequency of alpha rhythm in posterior brain areas (O1O2 electrodes) equal to or greater than 8.0 hz, and values below this range may be abnormal, and that women have a higher frequency than men. Reactivity ocular opening of the alpha rhythm remains despite advanced age and that its absence may also mean some functional impairment. The presence of slowing in the temporal regions, a finding that for many authors may be normal during senescence, was observed in this study in only 21% of the individuals, and had no significant correlation with the cognitive profile nor with the schooling level. The coherence for alpha band in posterior areas (P3P4 and O1O2) does not present significant alteration during the aging

Este avaliou as características do EEG numa população de indivíduos nonagenários cognitivamente normais tanto através da analise visual como espectral. A amostra constituía de 42 sujeitos com idade que variava de 90 a101 anos (media de 92 DP 3,0 anos) clinica e cognitivamente saudáveis vivendo em seus lares e totalmente independentes oriundos do ambulatório do grupo de neurologia cognitiva do HC (acompanhantes) e da Casa Idoso. Eles foram submetidos a uma entrevista, exame neurológico, avaliação neuropsicológica e um EEG digital com programas capacitados a realizar analise espectral e de analise de coerência.Foi avaliado através da analise visual o PF (pico de freqüência) da banda alfa em áreas posteriores,a reatividade alfa a abertura ocular ,a presença de atividade lenta nas regiões temporais, a ocorrência de variantes benignas e de atividade epileptiforme espontânea. Através da analise espectral foi determinado o PF espectral da banda alfa nas regiões occipitais, e a coerência inter-hemisférica para a banda alfa entre os eletrodos P3P4 e O1O2. Os resultados deste estudo confirmam os vários trabalhos da literatura, que concluíram que em indivíduos idosos saudáveis a freqüência do ritmo alfa nas regiões posteriores do cérebro nunca foi menos que 8,0 Hz, e que as mulheres apresentam um pico de freqüência maior que os homens. A reatividade do ritmo alfa à abertura ocular foi observada em 41 sujeitos (97,61%) do total, e atividade lenta nas regiões temporais em 9 indivíduos (21,42%) com predomínio no hemisfério cerebral esquerdo. O valor médio para a coerência inter-hemisférica obtida para banda alfa em P3P4 e O1O2 foi respectivamente 0,61(DP 0,11) e 0,65( DP 0,13), e não foi detectado nenhuma diferença significa relacionada ao sexo, e nem uma redução deste valor com o envelhecimento. Conclusão: indivíduos idosos nonagenários cognitivamente normais apresentam um pico de freqüência para o ritmo alfa em áreas posteriores do encéfalo (eletrodos O1O2) igual ou maior que 8,0 Hz, e que valores abaixo desta faixa pode significar anormalidade e que as mulheres tem uma freqüência maior que os homens. A reatividade à abertura ocular do ritmo alfa permanece apesar da idade avançada e que sua ausência pode significar algum comprometimento funcional. A presença de alentecimento nas regiões temporais um achado que para muitos autores pode ser normal durante a senescência, foi observada neste estudo em somente 21% dos indivíduos, e não teve nenhuma correlação significativa com o perfil cognitivo e nem com o nível de escolaridade. A coerência para banda alfa em áreas posteriores (P3P4 e O1O2) não apresenta alteração importante durante o envelhecimento / This study evaluated the characteristics of the EEG in a population of cognitively normal nonagenarian individuals both through visual and spectral analysis.The sample consisted of 42 subjects ranging from 90 to 101 years (median of 92 years), clinically and cognitively healthy living in their homes and totally independent. In the outpatient clinic of the cognitive neurology group of the HC (companions) and of the Elderly House (Casa do Idoso). They were submitted to an interview, neurological examination, neuropsychological assessment and a digital EEG with programs capable of performing spectral analysis and coherence analysis. Through the spectral analysis it was evaluated the PF (peak frequency) of the alpha band in posterior areas, the alpha reactivity to ocular opening, the presence of slow activity in the temporal regions, the occurrence of benign variants and spontaneous epileptiform activity. Through the spectral analysis the spectral PF of the alpha band was determined in the occipital regions, and the interhemispheric coherence for the alpha band between the electrodes P3P4 and O1O2. The results of this study confirm a various studies in the literature, which concluded that in healthy elderly individuals the frequency of the alpha rhythm in the posterior regions of the brain was never less than 8.0 Hz, and that women presents a higher frequency peak than men. Reactivity of the alpha rhythm to ocular opening was observed in 41 subjects (97.61%) of the total, and slow activity in the temporal regions in 9 individuals (21.42%) with predominance in the left cerebral hemisphere. The mean value for the interhemispheric coherence obtained for the alpha band in P3P4 and O1O2 was 0.61 (SD 0.11) and 0.65 (SD 0.13), respectively, and no difference was detected related to sex, nor reduction of this value with aging. CONCLUSION: Cognitively normal nonagenarians (90 to 101 years of age) have a peak frequency of alpha rhythm in posterior brain areas (O1O2 electrodes) equal to or greater than 8.0 hz, and values below this range may be abnormal, and that women have a higher frequency than men. Reactivity ocular opening of the alpha rhythm remains despite advanced age and that its absence may also mean some functional impairment. The presence of slowing in the temporal regions, a finding that for many authors may be normal during senescence, was observed in this study in only 21% of the individuals, and had no significant correlation with the cognitive profile nor with the schooling level. The coherence for alpha band in posterior areas (P3P4 and O1O2) does not present significant alteration during the aging