3,241 research outputs found
Dynamic Decomposition of Spatiotemporal Neural Signals
Neural signals are characterized by rich temporal and spatiotemporal dynamics
that reflect the organization of cortical networks. Theoretical research has
shown how neural networks can operate at different dynamic ranges that
correspond to specific types of information processing. Here we present a data
analysis framework that uses a linearized model of these dynamic states in
order to decompose the measured neural signal into a series of components that
capture both rhythmic and non-rhythmic neural activity. The method is based on
stochastic differential equations and Gaussian process regression. Through
computer simulations and analysis of magnetoencephalographic data, we
demonstrate the efficacy of the method in identifying meaningful modulations of
oscillatory signals corrupted by structured temporal and spatiotemporal noise.
These results suggest that the method is particularly suitable for the analysis
and interpretation of complex temporal and spatiotemporal neural signals
State-space solutions to the dynamic magnetoencephalography inverse problem using high performance computing
Determining the magnitude and location of neural sources within the brain
that are responsible for generating magnetoencephalography (MEG) signals
measured on the surface of the head is a challenging problem in functional
neuroimaging. The number of potential sources within the brain exceeds by an
order of magnitude the number of recording sites. As a consequence, the
estimates for the magnitude and location of the neural sources will be
ill-conditioned because of the underdetermined nature of the problem. One
well-known technique designed to address this imbalance is the minimum norm
estimator (MNE). This approach imposes an regularization constraint that
serves to stabilize and condition the source parameter estimates. However,
these classes of regularizer are static in time and do not consider the
temporal constraints inherent to the biophysics of the MEG experiment. In this
paper we propose a dynamic state-space model that accounts for both spatial and
temporal correlations within and across candidate intracortical sources. In our
model, the observation model is derived from the steady-state solution to
Maxwell's equations while the latent model representing neural dynamics is
given by a random walk process.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS483 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Statistical Mechanics and Information-Theoretic Perspectives on Complexity in the Earth System
Peer reviewedPublisher PD
Quantum Mechanics on Spacetime I: Spacetime State Realism
What ontology does realism about the quantum state suggest? The main extant
view in contemporary philosophy of physics is wave-function realism. We
elaborate the sense in which wave-function realism does provide an ontological
picture; and defend it from certain objections that have been raised against
it. However, there are good reasons to be dissatisfied with wave-function
realism, as we go on to elaborate. This motivates the development of an
opposing picture: what we call spacetime state realism; a view which takes the
states associated to spacetime regions as fundamental. This approach enjoys a
number of beneficial features, although, unlike wave-function realism, it
involves non-separability at the level of fundamental ontology. We investigate
the pros and cons of this non-separability, arguing that it is a quite
acceptable feature; even one which proves fruitful in the context of
relativistic covariance. A companion paper discusses the prospects for
combining a spacetime-based ontology with separability, along lines suggested
by Deutsch and HaydenComment: LaTeX; 29 pages, 1 Fig. Forthcoming in the British Journal for the
Philosophy of Scienc
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