A5065890445- Neural dynamics and brain function
- stochastic dynamics and bifurcation
- EEG and Brain-Computer Interfaces
- Functional Brain Connectivity Studies
- Neuroscience and Neuropharmacology Research
- Photoreceptor and optogenetics research
- Nonlinear Dynamics and Pattern Formation
- Advanced Thermodynamics and Statistical Mechanics
- Sleep and Wakefulness Research
- Advanced Memory and Neural Computing
- Anesthesia and Sedative Agents
- Connexins and lens biology
- Nicotinic Acetylcholine Receptors Study
- Enzyme Structure and Function
- Anesthesia and Neurotoxicity Research
- Neuroscience and Neural Engineering
- Optical Imaging and Spectroscopy Techniques
- Microbial Metabolic Engineering and Bioproduction
- Climate variability and models
- Quantum optics and atomic interactions
- Spectroscopy and Quantum Chemical Studies
- Protein Structure and Dynamics
- Oceanographic and Atmospheric Processes
- Circadian rhythm and melatonin
- Urban Heat Island Mitigation
University of Waikato
2015-2024
University of Auckland
2009
Waikato Hospital
1999
DairyNZ
1999
York University
1983-1984
How does physiological sleep affect the Bispectral Index (BIS)? We collected electroencephalographic (EEG) data from five subjects during early part of night, comparing changes in BIS with conventional EEG stages sleep.We found that was a consistent marker depth sleep. Light occurred at values 75-90, slow-wave 20-70, and rapid eye movement 75-92. The effects natural on seem to be similar general anesthesia BIS. may have role monitoring Implications: Electroencephalographic were decreased...
A1 Functional advantages of cell-type heterogeneity in neural circuits Tatyana O. Sharpee A2 Mesoscopic modeling propagating waves visual cortex Alain Destexhe A3 Dynamics and biomarkers mental disorders Mitsuo Kawato F1 Precise recruitment spiking output at theta frequencies requires dendritic h-channels multi-compartment models oriens-lacunosum/moleculare hippocampal interneurons Vladislav Sekulić, Frances K. Skinner F2 Kernel methods reconstruction current sources from extracellular...
Many enzymes display non-Arrhenius behavior with curved Arrhenius plots in the absence of denaturation. There has been significant debate about origin this and recently role activation heat capacity (ΔCP⧧) widely discussed. If enzyme-catalyzed reactions occur appreciable negative values ΔCP⧧ (arising from narrowing conformational space along reaction coordinate), then are a consequence. To investigate these phenomena detail, we have collected high precision temperature-rate data over wide...
We present a model for the dynamics of cerebral cortex in which inputs to neuronal assemblies are treated as random Gaussian fluctuations about mean value. incorporate effect general anesthetic agents on modulation inhibitory neurotransmitter rate constant. Stochastic differential equations derived state variable ${h}_{e},$ average excitatory soma potential, coherent believed be source scalp-measured electroencephalogram (EEG) signals. Using this stochastic approach we derive stationary...
Chlorophyll red-edge descriptors have been used to estimate leaf nitrogen concentration in ryegrass ( Lolium spp.) pasture. Two-layer model calculations predict the influence of chlorophyll content and Leaf Area Index (LAI) on shape location peaks observed derivative spectra a canopy. The complex structure resulting precluded extracting wavelengths by fitting inverted Gaussian curves reflectance profiles. Fitting combination three sigmoid calculated provided better representation subsequent...
How does physiological sleep affect the Bispectral Index (BIS)? We collected electroencephalographic (EEG) data from five subjects during early part of night, comparing changes in BIS with conventional EEG stages sleep.We found that was a consistent marker depth sleep. Light occurred at values 75-90, slow-wave 20-70, and rapid eye movement 75-92. The effects natural on seem to be similar general anesthesia BIS. may have role monitoring Implications: Electroencephalographic were decreased...
Commonly used general anaesthetics cause a decrease in the spectral entropy of electroencephalogram as patient transits from conscious to unconscious state. Although is configurational entropy, it plausible that may be acting reliable indicator real changes cortical neuronal interactions. Using mean field theory, activity cerebral cortex modelled fluctuations soma potential around equilibrium states. In adiabatic limit, stochastic differential equations take form an Ornstein-Uhlenbeck...
The role of gap junctions in seizures is an area intense research. Many groups have reported anticonvulsant effects junction blockade, strengthening the case for a ictogenesis. cerebral cortex underrepresented this body We investigated effect blockade on seizure-like activity rat and mouse slices.Seizure-like was induced by perfusing with low-magnesium artificial cerebrospinal fluid. three blockers cortical slices; quinine (200 400 microm), quinidine (100 200 carbenoxolone microm). In...
Slow oscillations in neuronal activity the human brain are defining feature of scalp-measured electroencephalography taken under general anesthesia. A theoretical investigation a model for cortex reveals that slow spatiotemporal patterns emerge spontaneously as result chemically modified balancing act between two instabilities cortical dynamics---one to spatial organizations and other temporal bifurcation. Long-range interneuronal communication across is shown be crucial pattern formation.
In a recent paper the authors developed stochastic model for response of cerebral cortex to general anesthetic agent. The predicted that there would be an anesthetic-induced phase change at point transition into unconsciousness, manifested as divergence in electroencephalogram spectral power, and energy distribution from being relatively broadband conscious state strongly biased towards much lower frequencies unconscious state. Both predictions have been verified clinical measurements....
In a recent series of papers, the authors have developed stochastic theory to describe electrical response spatially homogeneous cerebral cortex infusion general anesthetic agent. We showed that by modeling GABAergic (propofol-like) drug effect as prolongation inhibitory postsynaptic impulse response, we obtain prediction there will be hysteretically separated pair first-order phase transitions in population-average excitatory soma voltage, first occurring at point induction unconsciousness,...
GENERAL anesthesia is a state in which cerebral activity usually profoundly suppressed. It paradoxical that some general anesthetic agents—drugs whose primary action to decrease central nervous system and have been widely used treat seizures—can also provoke cortical seizures when the patient deeply anesthetized.1–3Traditionally, explanation for this phenomenon has sought at molecular or synaptic level of description, by finding differences between drugs commonly precipitate seizure those do...
One of the grand puzzles in neuroscience is establishing link between cognition and disparate patterns spontaneous task-induced brain activity that can be measured clinically using a wide range detection modalities such as scalp electrodes imaging tomography. High-level function not single-neuron property, yet emerges cooperative phenomenon multiply-interacting populations neurons. Therefore fruitful modeling approach to picture cerebral cortex continuum characterized by parameters have been...
The Wilson-Cowan neural field equations describe the dynamical behavior of a 1-D continuum excitatory and inhibitory cortical aggregates, using pair coupled integro-differential equations. Here we use bifurcation theory small-noise linear stochastics to study range phase transitions-sudden qualitative changes in state system emerging from bifurcation-accessible network. Specifically, examine saddle-node, Hopf, Turing, Turing-Hopf instabilities. We introduce stochasticity by adding...
The electroencephalogram (EEG) patterns recorded during general anesthetic-induced coma are closely similar to those seen slow-wave sleep, the deepest stage of natural sleep; both states show dominated by large amplitude slow waves. Slow oscillations believed be important for memory consolidation sleep. Tracking emergence transition unconsciousness may help us identify drug-induced alterations underlying brain state, and provide insight into mechanisms anesthesia. Although cellular-based...
Characterizing brain dynamics during anesthesia is a main current challenge in study. Several single channel electroencephalogram (EEG)-based commercial monitors like the Bispectral index (BIS) have suggested to examine EEG signal. But, BIS has obtained numerous critiques. In this study, we evaluate concentration-dependent effect of propofol on long-range frontal-temporal synchronization signals collected from eight subjects controlled induction and recovery design. We used order patterns...
In our two recent papers [M.L. Steyn-Ross et al., Phys. Rev. E 60, 7299 (1999); 64, 011917 (2001)] we presented clinical evidence for a general anesthetic-induced phase change in the cerebral cortex, and showed how significant features of cortical (biphasic power surge, spectral energy redistribution, "heat capacity" divergence), could be explained using stochastic single-macrocolumn model cortex. The predictions were based on rather strong "adiabatic" assumptions which assert that...
We present a fully-quantum-mechanical theory of the intracavity interaction coherent light with semiconductors. Interaction is assumed to occur via excitons. Using master-equation approach we include such effects as exciton-lattice and exciton-exciton interactions. In two cases high low exciton densities, steady-state analysis reveals bistability hysteresis in system. Bistability dispersive absorptive nature both number output intensity, dependent on input intensity found. The displayed...