RESUMO
This paper presents a unified mathematical derivation of the asymptotic behaviour of the three main forms of partial directed coherence (PDC). Numerical examples are used to contrast PDC, gPDC (generalized PDC) and iPDC (information PDC) as to meaning and applicability and, more importantly, to show their essential statistical equivalence insofar as connectivity inference is concerned.
Assuntos
Algoritmos , Modelos Biológicos , Modelos Estatísticos , Simulação por ComputadorRESUMO
This paper introduces a new frequency-domain approach to describe the relationships (direction of information flow) between multivariate time series based on the decomposition of multivariate partial coherences computed from multivariate autoregressive models. We discuss its application and compare its performance to other approaches to the problem of determining neural structure relations from the simultaneous measurement of neural electrophysiological signals. The new concept is shown to reflect a frequency-domain representation of the concept of Granger causality.
Assuntos
Córtex Cerebral/fisiologia , Eletroencefalografia , Hipocampo/fisiologia , Modelos Neurológicos , Sono/fisiologia , Humanos , Análise MultivariadaRESUMO
This paper discusses the employment of non-parametric non-linear prediction algorithms to investigate non-linear dynamics in the rhythmic brain activity of rats. Three algorithms (Sugihara-May Simplex, K-neighbour and Casdagli's) were tested yielding similar prediction results which--when subject to a suitable bootstrap based t-tests--revealed that the theta waves recorded in rat brains cannot have their intrinsic non-linearity dismissed at a significance of 0.05.
Assuntos
Algoritmos , Hipocampo/fisiologia , Ratos/fisiologia , Ritmo Teta/veterinária , Animais , Previsões , Dinâmica não Linear , Análise Numérica Assistida por Computador , Estatísticas não ParamétricasRESUMO
This paper illustrates the use of the recently introduced method of partial directed coherence in approaching how interactions among neural structures change over short time spans that characterize well defined behavioral states. Central to the method is its use of multivariate time series modelling in conjunction with the concept of Granger causality. Simulated neural network models were used to illustrate the technique's power and limitations when dealing with neural spiking data. This was followed by the analysis of multi-unit activity data illustrating dynamical change in the interaction of thalamo-cortical structures in a behaving rat.
Assuntos
Comunicação Celular/fisiologia , Modelos Neurológicos , Neurônios/fisiologia , Potenciais de Ação/fisiologia , Animais , Comportamento Animal/fisiologia , Córtex Cerebral/fisiologia , Simulação por Computador , Redes Neurais de Computação , Ratos , Tálamo/fisiologia , Fatores de TempoRESUMO
Electro-oscillographic recordings show that when rats wake up, behavioral manifestations such as head dorsal extension and snout and eye movements (which occur in this sequence), occasionally followed by brief ear and limb twitches, are preceded by and are simultaneous with theta waves (around 6.5 Hz in frequency) in neocortical areas 3 and 17 and in the hippocampus. Heart rate increases when the animal passes from synchronized sleep to relaxed wakefulness to exploratory behavior. During desynchronized sleep theta waves, similar to those found during alertness, usually precede and are simultaneous with rostrum and eye movements and brief ear and limb twitches. Heart rate also increases during dreaming activity. A high degree of coherence (near 1.0) was found among theta bursts in different hippocampal areas in both highly attentive alertness and dreaming. It is suggested that theta waves are related to attention as part of some kinds of behavior and of the process of dream shaping and expression, both characterized by consciousness.
Assuntos
Comportamento Animal/fisiologia , Sonhos/fisiologia , Ritmo Teta , Vigília/fisiologia , Animais , Sincronização Cortical , Eletromiografia , Feminino , Masculino , Ratos , Ratos WistarRESUMO
Electro-oscillographic recordings show that when up, behavioral manifestations such as head dorsal extension and snout and eye movements (which occur in this sequence) occasionally followed by brief ear areas 3 and 17 and in the hippocampus. Heart rate increases when the animal passes from synchronized sleep to relaxed wakefulness to exploratory behavior. During desynchronized sleep theta waves, similar to those found during alertness, usually precede and are simultaneous with rostrum and eye movements and brief ear and limb twitches. Heart rate also increases during dreaming activity. A high degree of coherence (near 1.0) was found among theta bursts in different hippocampal areas in both highly attentive alertness and dreaming. It is suggested that theta waves are related to attention as part of some kinds of behavior and of the process of dream shaping and expression, both characterized by consciousness
Assuntos
Ratos , Atenção , Comportamento Animal , Consciência , Sono/efeitos da radiação , Ritmo Teta , Transtornos do Sono-Vigília , Frequência Cardíaca , HipocampoRESUMO
The application of a microcomputer-based system (the Connection system) designed to deal with neuroanatomical information commonly analyzed by researchers and involved in the study of structural properties of neural circuits is presented. This system can be employed at first as a readily-accessible database containing physiological and anatomical data from nuclei of the central nervous system which define a network with up to 45 elements and their subdivisions and connections. Once the database from a specific network is built and stored in a file, routines of this system can be used to classify the nuclei in term of their afferents and efferents and also to display all possible pathways linking any pair of nuclei and their respective length (number of synapses). The role of such a system as an auxiliary tool in neuroanatomical and electrophysiological research is discussed by presenting the results obtained from the analysis of the neural circuits involved in cardiovascular function control in higher vertebrates.
Assuntos
Sistema Cardiovascular/inervação , Microcomputadores , Modelos Neurológicos , Vias Neurais/anatomia & histologia , Software , Algoritmos , Sistemas de Informação , Design de SoftwareRESUMO
The electrical activity of the posterior thalamic nuclear complex was studied in rats and related to the simultaneous hippocampal electro-oscillogram. Electrocorticographic tracings and spectral analysis showed that during attentive wakefulness the electro-oscillogram peaked at 8 Hz and in desynchronized sleep it oscillated at regular frequencies between 8 and 9 Hz. In quiet wakefulness, frequency was lower (around 6 Hz) and during synchronized sleep rhythmicity disappeared. The electrophysiological patterns during wakefulness and desynchronized sleep are proposed to be linked to the retrieval and combination of information for the generation of attention and dream content.
Assuntos
Hipocampo/fisiologia , Sono/fisiologia , Núcleos Talâmicos/fisiologia , Vigília/fisiologia , Animais , Eletrofisiologia/métodos , Feminino , Masculino , Oscilometria , Ratos , Ratos EndogâmicosRESUMO
Establishing the stationarity and statistical distribution of potentials recorded from the nervous system is crucial for the application of frequency analysis. Both parameters were determined in the electrocorticograms of six adult Wistar rats during wakefulness and desynchronized sleep, during both of which desynchronization prevails. Stationarity of the signals was found to occur during at least 20 s in both states of the wakefulness-sleep cycle. A normal distribution was also found for at least 6.7 s. These findings provide strong support for the use of frequency analysis of brain waves as a reliable method to quantify neural electro-oscillograms.
Assuntos
Córtex Cerebral/fisiologia , Sono/fisiologia , Vigília/fisiologia , Animais , Eletrofisiologia , Oscilometria , Ratos , Ratos EndogâmicosRESUMO
The electrical activity of the posterior thalamic nuclear complex was studied in rats and related to the simultaneous hippocampal electro-oscillogram. Electrocorticographic tracings and spectral analysis showed that during attentive wakefulness the electro-oscillogram peaked at 8 Hz and in desynchronized sleep it oscillated at regular frequencies between 8 and 9 Hz. In quiet wakefulness, frequency was lower (around 5 Hz) and during synchronized sleep rhytmicity disppeared. The electrophysiological patterns during wakefulness and desynchronized sleep are proposed to be linked to the retrieeval and combination of information for the generation of attention and dream content
Assuntos
Ratos , Animais , Masculino , Feminino , Hipocampo/fisiologia , Núcleos Talâmicos/fisiologia , Sono/fisiologia , Vigília/fisiologia , Eletrofisiologia , Oscilometria , Ratos Wistar , Análise EspectralRESUMO
Establishing the stationarity and statistical distribution of potentials recorded from the nervous system is cricial for the application of frequency analysis. Both parameters were determined in the electrocorticograms of six adult Wistar rats during wakefulness and desynchronized sleep, during both of which desinchronization prevails. Stationarity of the signals was found to occur during at least 20 s in both states of the wakefulness-sleep cycle. A normal distribution was also found for at least 6.7 s. These findings provide strong support for the use of frequency analysis of brain waves as a reliable method to quantify neural electro-oscillograms