916 research outputs found
Correlations and functional connections in a population of grid cells
We study the statistics of spike trains of simultaneously recorded grid cells
in freely behaving rats. We evaluate pairwise correlations between these cells
and, using a generalized linear model (kinetic Ising model), study their
functional connectivity. Even when we account for the covariations in firing
rates due to overlapping fields, both the pairwise correlations and functional
connections decay as a function of the shortest distance between the vertices
of the spatial firing pattern of pairs of grid cells, i.e. their phase
difference. The functional connectivity takes positive values between cells
with nearby phases and approaches zero or negative values for larger phase
differences. We also find similar results when, in addition to correlations due
to overlapping fields, we account for correlations due to theta oscillations
and head directional inputs. The inferred connections between neurons can be
both negative and positive regardless of whether the cells share common spatial
firing characteristics, that is, whether they belong to the same modules, or
not. The mean strength of these inferred connections is close to zero, but the
strongest inferred connections are found between cells of the same module.
Taken together, our results suggest that grid cells in the same module do
indeed form a local network of interconnected neurons with a functional
connectivity that supports a role for attractor dynamics in the generation of
the grid pattern.Comment: Accepted for publication in PLoS Computational Biolog
Detecting multineuronal temporal patterns in parallel spike trains
We present a non-parametric and computationally efficient method that detects spatiotemporal firing patterns and pattern sequences in parallel spike trains and tests whether the observed numbers of repeating patterns and sequences on a given timescale are significantly different from those expected by chance. The method is generally applicable and uncovers coordinated activity with arbitrary precision by comparing it to appropriate surrogate data. The analysis of coherent patterns of spatially and temporally distributed spiking activity on various timescales enables the immediate tracking of diverse qualities of coordinated firing related to neuronal state changes and information processing. We apply the method to simulated data and multineuronal recordings from rat visual cortex and show that it reliably discriminates between data sets with random pattern occurrences and with additional exactly repeating spatiotemporal patterns and pattern sequences. Multineuronal cortical spiking activity appears to be precisely coordinated and exhibits a sequential organization beyond the cell assembly concept
VIOLA - A multi-purpose and web-based visualization tool for neuronal-network simulation output
Neuronal network models and corresponding computer simulations are invaluable
tools to aid the interpretation of the relationship between neuron properties,
connectivity and measured activity in cortical tissue. Spatiotemporal patterns
of activity propagating across the cortical surface as observed experimentally
can for example be described by neuronal network models with layered geometry
and distance-dependent connectivity. The interpretation of the resulting stream
of multi-modal and multi-dimensional simulation data calls for integrating
interactive visualization steps into existing simulation-analysis workflows.
Here, we present a set of interactive visualization concepts called views for
the visual analysis of activity data in topological network models, and a
corresponding reference implementation VIOLA (VIsualization Of Layer Activity).
The software is a lightweight, open-source, web-based and platform-independent
application combining and adapting modern interactive visualization paradigms,
such as coordinated multiple views, for massively parallel neurophysiological
data. For a use-case demonstration we consider spiking activity data of a
two-population, layered point-neuron network model subject to a spatially
confined excitation originating from an external population. With the multiple
coordinated views, an explorative and qualitative assessment of the
spatiotemporal features of neuronal activity can be performed upfront of a
detailed quantitative data analysis of specific aspects of the data.
Furthermore, ongoing efforts including the European Human Brain Project aim at
providing online user portals for integrated model development, simulation,
analysis and provenance tracking, wherein interactive visual analysis tools are
one component. Browser-compatible, web-technology based solutions are therefore
required. Within this scope, with VIOLA we provide a first prototype.Comment: 38 pages, 10 figures, 3 table
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