Asymmetrical Electroencephalographic Change of Human Brain During Sleep Onset Period

OBJECTIVE: Human cerebral hemisphere is known to function asymmetrically with daytime left hemisphere superiority in most right-handed persons. It may have relevance to the localization of specific function of the brain. This study attempted to reveal whether the functional cerebral asymmetry in the wakeful state is still maintained throughout the sleep onset period. METHODS: Thirty-channel EEG was recorded in 61 healthy subjects. The EEG power spectra of each of the seven frequencies were compared between the two kinds of 30-second states; the wakeful stage and the late-sleep stage 1. RESULTS: The asymmetrical indices of sleep stage 1 at several fronto-central leads were decreased in the delta, theta, alpha-2, and all beta bands. Conversely, at parts of parieto-occipital leads showed an increase in the indices of the theta, alphas, beta-1, and beta-2 bands. Any fronto-central leads did not show an increase in the index, and no parieto-occipital leads showed a decrease. CONCLUSION: During the sleep onset period, power spectral asymmetry of the brain showed a different pattern from the wakeful stage. This asymmetrical pattern of EEG powers may suggest a reversal of the left hemispheric dominance during sleep.

Cerebral Asymmetry and Dominance in Man.

The two human cerebral hemispheres are not mirror images of each other. They show anatomical and functional differences that are termed as cerebral asymmetries. The most striking differences in right-handed people are Broca’s motor areas of speech in the left inferior frontal gyrus and Wernicke’s area for language comprehension and speech production in the left posterior temporal and inferior parietal lobules. These examples have lead to the overall concept of dominant left and subordinate right cerebral hemispheres. Other structural asymmetries are revealed in the perisylvian area, surface area around the central fissure, cortical thickness, cerebral rotation, the volume of the lateral ventricle, lateral geniculate body, posterior cerebral and circle of Willis arteries, deep medullary veins, and type of nervous system of individuals. Functional cerebral asymmetries are also reported regarding verbal and linguistic functions, mathematical skills, analytical thinking, functions of corticobulbar, corticospinal and corticobasal pathways, functional organization of the prefrontal cortex (PFC), orbitofrontal cortex (OFC) and ventromedial temporal cortex (fusiform gyrus, FG), as well as amyloid-β deposition and metabolism. Cerebral asymmetries are thought to play an essential role in the pathogenesis of clinical disorders as aphasia, unilateral left brain lesion, adiadochokinesa, autism spectrum disorder (ASD), corticobasal syndrome, Parkinson’s disease (PD), Alzheimer's disease, and adolescents with idiopathic scoliosis (AIS). Age and sex related asymmetries have been sometimes postulated. Genetic, environmental and callosal factors are mentioned to underlie the etiology of cerebral asymmetries. Comparatively, functional, and neuroanatomical asymmetries do exist in nonhuman primates.

Neuroimmunological Aberrations and Cerebral Asymmetry Abnormalities in Schizophrenia: Select Perspectives on Pathogenesis

Within the wide-ranging gamut of factors that comprise gene-environment interactions postulated to underlie schizophrenia, the crosstalk between environmental factors and feto-maternal immune components has been put forth as one of the important mechanisms that increase the risk towards schizophrenia in the offspring. Interestingly, immune factors have been shown to critically modulate the brain development during the prenatal stages. Moreover the past many decades, influential theoretical propositions and evidence base (albeit not unequivocally) have compellingly linked prenatal sex hormonal status to critically provoke long lasting immunological changes and subsequently affect developmental programming of cerebral asymmetry in schizophrenia. In this review, we summarize the select perspectives emphasizing the role of neuroimmunoendocrine pathways in anomalous cerebral asymmetry in contemporary understanding of schizophrenia pathogenesis.

Comportamento rotacional em Teste de Nado Livre como um modelo em roedores para estudo da neurotoxicidade do chumbo durante a vida adulta / Rotational behavior in free-swimming test as a model in rodents to study the neurotoxicity of lead during adulthood

A exposição ao chumbo ainda permanece como um sério problema de saúde pública, especialmente nos países em desenvolvimento como o Brasil. Apesar do número crescente de estudos mostrando déficits neurocomportamentais em indivíduos expostos ocupacionalmente ao chumbo, os mecanismos envolvidos com a manifestação destes transtornos permanecem pouco conhecidos. Desta forma, o uso de modelos animais abre grandes possibilidades, não somente de investigação dos mecanismos biológicos envolvidos com a toxicidade do chumbo, mas também na elaboração de estratégias para proteção e/ou reversão dos seus efeitos. Portanto, o objetivo central deste trabalho foi avaliar o potencial do comportamento rotacional, medido em testes de nado livre, como um modelo em roedores para estudo dos efeitos neurocomportamentais da exposição ao chumbo durante a vida adulta. Para tanto, foram realizados três estudos. No primeiro, avaliamos os efeitos da exposição subcrônica (60-90 dias) ao chumbo sobre a atividade locomotora no teste de nado livre e em um teste tradicionalmente utilizado para avaliar a ação de substâncias neurotóxicas sobre a locomoção, o campo aberto. Enquanto no campo aberto não foram encontradas diferenças significativas entre o grupo exposto e o grupo controle, no teste de nado livre, os animais expostos ao chumbo apresentaram maior atividade natatória e menor quantidade de alternâncias espontâneas no sentido de natação que o grupo controle. No segundo estudo, observamos que a magnitude dos efeitos do chumbo no teste de nado livre variou em função da consistência da lateralidade, sendo os resultados mais pronunciados no grupo de animais não consistentes (com menor lateralidade). Nos dois estudos, os efeitos do chumbo foram independentes do nível de chumbo em sangue (PbS) dos animais expostos. No terceiro estudo, mostramos um aumento dos níveis de glutationa oxidada no cérebro somente no grupo de animais com PbS acima de 60 ug/dL...

Lead exposure continues to be a serious public health problem, particularly in developing countries such as Brazil. Despite the increasing number of studies showing neurobehavioral deficits in people occupationally exposed to lead, the mechanisms involved in the manifestation of these problems remain largely unknown. In this sense, the use of animal models opens up the possibility of not only investigating the biological mechanisms associated with lead toxicity but also of elaborating strategies aiming at protecting individuals against its ill effects or even reversing those that already present. Therefore, the main objective of the present work was to assess the potential of the rotatory behavior in the free-swimming test as a rodent model for studying of the neurobehavioral effects adult life lead exposure. In the first study, we analyzed the effect of subchronic lead exposure on motor activity in the free-swimming test and in open-field test, which has been traditionally used to assess the effects of toxic substances on locomotion. While no significant differences were observed between the exposed and control groups in the open-field, in the free-swimming test, lead exposed animals displayed increased natatory activity and fewer spontaneous alterations in the direction of locomotion in comparison with the control group. In the second study, we observed that the magnitude of the effects of lead exposure varied as a function of the consistency of the lateralization, being the results more pronounced in inconsistent animals (lesser degree of lateralization). In both studies, the effects of lead were not dependent on blood levels of lead exposed animals. In the third study, we demonstrated a significant increase in the levels of oxidized glutathione in the brain (indicative of oxidative stress) only in the group of animals that had lead levels above 60 ug/dL. Based in these results, we can conclude that: 1) Rotatory behavior in the free-swimming test...