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46
A neural mass model for MEG/EEG: coupling and neuronal dynamics
- NeuroImage
, 2003
"... Although MEG/EEG signals are highly variable, systematic changes in distinct frequency bands are commonly encountered. These frequency-specific changes represent robust neural correlates of cognitive or perceptual processes (for example, alpha rhythms emerge on closing the eyes). However, their func ..."
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Cited by 81 (21 self)
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Although MEG/EEG signals are highly variable, systematic changes in distinct frequency bands are commonly encountered. These frequency-specific changes represent robust neural correlates of cognitive or perceptual processes (for example, alpha rhythms emerge on closing the eyes). However, their functional significance remains a matter of debate. Some of the mechanisms that generate these signals are known at the cellular level and rest on a balance of excitatory and inhibitory interactions within and between populations of neurons. The kinetics of the ensuing population dynamics determine the frequency of oscillations. In this work we extended the classical nonlinear lumped-parameter model of alpha rhythms, initially developed by Lopes da Silva and colleagues [Kybernetik 15 (1974) 27], to generate more complex dynamics. We show that the whole spectrum of MEG/EEG signals can be reproduced within the oscillatory regime of this model by simply changing the population kinetics. We used the model to examine the influence of coupling strength and propagation delay on the rhythms generated by coupled cortical areas. The main findings were that (1) coupling induces phase-locked activity, with a phase shift of 0 or π when the coupling is bidirectional, and (2) both coupling and propagation delay are critical determinants of the MEG/EEG spectrum. In forthcoming articles, we will use this model to (1) estimate how neuronal interactions are expressed in MEG/EEG oscillations and establish the construct validity of various indices of nonlinear coupling, and (2) generate event-related transients to derive physiologically informed basis functions for statistical modelling of average evoked responses.
Stability and bifurcations in neural fields with finite propagation speed and general connectivity
- SIAM J. APPL. MATH
, 2005
"... A stability analysis is presented for neural field equations in the presence of finite propagation speed along axons and for a general class of connectivity kernels and synaptic properties. Sufficient conditions are given for the stability of equilibrium solutions. It is shown that the propagation ..."
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Cited by 26 (5 self)
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A stability analysis is presented for neural field equations in the presence of finite propagation speed along axons and for a general class of connectivity kernels and synaptic properties. Sufficient conditions are given for the stability of equilibrium solutions. It is shown that the propagation delays play a significant role in nonstationary bifurcations of equilibria, whereas the stationary bifurcations depend only on the connectivity kernel. In the case of nonstationary bifurcations, bounds are determined on the frequencies of the resulting oscillatory solutions. A perturbative scheme is used to calculate the types of bifurcations leading to spatial patterns, oscillations, and traveling waves. For high propagation speeds a simple method is derived that allows the determination of the bifurcation type by visual inspection of the Fourier transforms of the kernel and its first moment. Results are numerically illustrated on a class of neurologically plausible systems with combinations of Gaussian excitatory and inhibitory connections.
Massage therapy of moderate and light pressure and vibrator effects on EEG and heart rate
- International Journal of Neuroscience
, 2004
"... Three types of commonly used massage therapy techniques were as-sessed in a sample of 36 healthy adults, randomly assigned to: (1) moderate massage, (2) light massage, or (3) vibratory stimulation group (n = 12 per group). Changes in anxiety and stress were assessed, and EEG and EKG were recorded. A ..."
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Cited by 14 (1 self)
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Three types of commonly used massage therapy techniques were as-sessed in a sample of 36 healthy adults, randomly assigned to: (1) moderate massage, (2) light massage, or (3) vibratory stimulation group (n = 12 per group). Changes in anxiety and stress were assessed, and EEG and EKG were recorded. Anxiety scores decreased for all groups, but the moderate pressure massage group reported the greatest de-crease in stress. The moderate massage group also experienced a de-crease in heart rate and EEG changes including an increase in delta and a decrease in alpha and beta activity, suggesting a relaxation re-sponse. Finally, this group showed increased positive affect, as indi-cated by a shift toward left frontal EEG activation. The light massage group showed increased arousal, as indicated by decreased delta and increased deta activity and increased heart rate. The vibratory stimula-tion group also showed increased arousal, as indicated by increased heart rate and increased theta, alpha, and beta activity.
Existence and properties of solutions for neural field equations
, 2007
"... The first goal of this work is to study solvability of the neural field equation ∂u(x, t) τ − u(x, t) = w(x, y)f(u(y, t)) dy, x ∈ R ∂t m, t> 0, R m which is an integro-differential equation in m+1 dimensions. In particular, we show the existence of global solutions for smooth activation function ..."
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Cited by 9 (0 self)
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The first goal of this work is to study solvability of the neural field equation ∂u(x, t) τ − u(x, t) = w(x, y)f(u(y, t)) dy, x ∈ R ∂t m, t> 0, R m which is an integro-differential equation in m+1 dimensions. In particular, we show the existence of global solutions for smooth activation functions f with values in [0, 1] and L 1 kernels w via the Banach fixpoint theorem. For a Heaviside type activation function f we show that the above approach fails. However, with slightly more regularity on the kernel function w (we use Hölder continuity with respect to the argument x) we can employ compactness arguments, integral equation techniques and the results for smooth nonlinearity functions to obtain a global existence result in a weaker space. Finally, general estimates on the speed and durability of waves are derived. We show that compactly supported waves with directed kernels (i.e. w(x, y) ≤ 0 for x ≤ y) decay exponentially after a finite time and that the field has a well defined finite speed. 1
A comparison of the electroencephalogram between institutionalized and community children in Romania
- Journal of Cognitive Neuroscience
, 2004
"... & Electroencephalographic (EEG) data were collected from a sample of institutionalized infants and young children in Bucharest, Romania, and were compared with EEG data from age-matched children from the local community who had never been institutionalized and who were living with their families ..."
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Cited by 5 (2 self)
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& Electroencephalographic (EEG) data were collected from a sample of institutionalized infants and young children in Bucharest, Romania, and were compared with EEG data from age-matched children from the local community who had never been institutionalized and who were living with their families in the Bucharest area. Compared with the never-institutionalized group, the institutionalized group showed a pattern of increased low-frequency (theta) power in posterior scalp regions and decreased high-frequency (alpha and beta) power, particularly at frontal and temporal electrode sites. This finding is consistent with EEG studies of children facing environmental adversity and children with learning disorders. The institutionalized group also showed less marked hemispheric EEG asymmetries than the never-institutionalized group, particularly in the temporal region. The results are discussed in the context of two models: that the pattern of EEG in the institutionalized children reflects a maturational lag in nervous system development, or that it reflects tonic cortical hypoactivation. &
Reviewer(s): Review of Brain-Computer Interfaces based on the P300 evoked potential
"... Brain-computer interfaces (BCIs) can be used as a communication and control systems. BCIs are in principle intended for people with motor disabilities, yet applications for healthy users have increasingly been proposed. A BCI is a communication system in which intentions can be sent to the external ..."
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Brain-computer interfaces (BCIs) can be used as a communication and control systems. BCIs are in principle intended for people with motor disabilities, yet applications for healthy users have increasingly been proposed. A BCI is a communication system in which intentions can be sent to the external world without the use of normal peripheral nerves or muscles. Several electrophysiological characteristics can be extracted from the human EEG to control the BCI system. The P300 evoked potential is used in many BCI systems because it is a typical and naive response to a desired choice. An important advantage of a P300-based BCI is that it requires no user training. However, the P300 can be influenced by different human factors such as attention, motivation and fatigue. The extent to which such factors affect BCI operation remain to be explored. The same applies to BCI operation in real life situations. Important applications are word-spelling devices (e.g. P300 speller) wheelchair control using a P300-based BCI. Present day BCIs still have shortcomings (e.g. low transfer rates) that prevent
The CEMI field theory
- The Emerging Physics of Consciousness
, 2006
"... Abstract: Several theories of consciousness first described about a decade ago, including the conscious electromagnetic information (CEMI) field theory, claimed that the substrate of consciousness is the brain’s electromagnetic (EM) field. These theories were prompted by the observation, in many div ..."
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Abstract: Several theories of consciousness first described about a decade ago, including the conscious electromagnetic information (CEMI) field theory, claimed that the substrate of consciousness is the brain’s electromagnetic (EM) field. These theories were prompted by the observation, in many diverse systems, that synchronous neuronal firing, which generates coherent EM fields, was a strong correlate of attention, awareness, and consciousness. However, when these theo-ries were first described there was no direct evidence that synchro-nous firing was actually functional, rather than an epiphenomenon of brain function. Additionally, any EM field-based consciousness would be a ‘ghost in the machine ’ unless the brain’s endogenous EM field is also able to influence neuron firing. Once again, when these theories were first described, there was only indirect evidence that the brain’s EM field influenced neuron firing patterns in the brain. In this paper I describe recent experimental evidence which demonstrate that synchronous neuronal firing does indeed have a functional role in the brain; and also that the brain’s endogenous EM field is involved in recruiting neurons to synchronously firing networks. The new data point to a new and unappreciated form of neural communication in the brain that is likely to have significance for all theories of con-sciousness. I describe an extension of the CEMI field theory that incorporates these recent experimental findings and integrates the theory with the ‘communication through coherence ’ hypothesis.
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"... Spontaneous default mode network phase-locking moderates performance perceptions under stereotype threat ..."
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Spontaneous default mode network phase-locking moderates performance perceptions under stereotype threat
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"... Spontaneous default mode network phase-locking moderates performance perceptions under stereotype threat ..."
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Spontaneous default mode network phase-locking moderates performance perceptions under stereotype threat
DMN and Stereotype Threat 1 Running Head: DEFAULT MODE PHASE-LOCKING AND STEREOTYPE THREAT Spontaneous Default Mode Network Phase-locking Moderates Performance Perceptions under Stereotype Threat
"... D ow nloaded from DMN and Stereotype Threat 2 The current study assessed whether individual differences in self-oriented neural processing were associated with performance perceptions of minority students under stereotype threat. Resting EEG activity recorded in white and minority participants was u ..."
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D ow nloaded from DMN and Stereotype Threat 2 The current study assessed whether individual differences in self-oriented neural processing were associated with performance perceptions of minority students under stereotype threat. Resting EEG activity recorded in white and minority participants was used to predict later estimates of task errors and self-doubt on a presumed measure of intelligence. We assessed spontaneous phase-locking between dipole sources in left lateral parietal cortex (LPC), precuneus/posterior cingulate cortex (p/PCC), and medial prefrontal cortex (MPFC); three regions of the default mode network (DMN) that are integral for self-oriented processing. Results revealed that minorities with greater LPC-p/PCC phase-locking in the theta band reported more accurate error estimations. All individuals experienced less self-doubt to the extent they exhibited greater LPC-MPFC phase-locking in the alpha band but this effect was driven by minorities. Minorities also reported more self-doubt to the extent they overestimated errors. Findings reveal novel neural moderators of stereotype threat effects on subjective experience. Spontaneous synchronization between DMN regions may play a role in anticipatory coping mechanisms that buffer individuals from stereotype threat.