Ch 9. Rhythms and Ch 9. Rhythms and Synchrony Synchrony 9.7 9.7 Adaptive Cooperative Systems, Adaptive Cooperative Systems, Martin Beckerman, 1997. Martin Beckerman, 1997. Summarized by M.-O. Heo Biointelligence Laboratory, Seoul National University http://bi.snu.ac.kr/
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Ch 9. Rhythms and Synchrony 9.7 Adaptive Cooperative Systems, Martin Beckerman, 1997. Summarized by M.-O. Heo Biointelligence Laboratory, Seoul National.
Mean-Field Model of Cortical Oscillations How limit cycle oscillations may arise in a single cortical column in response to external stimuli? 3 (C) 2009, SNU Biointelligence Lab,
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Ch 9. Rhythms and SynchronyCh 9. Rhythms and Synchrony9.79.7
9.7 Oscillations and Synchrony in the Visual Cortex and Hippocampus 9.7.1 Mean-Field Model of Cortical Oscillations 9.7.2 Delay Connections and Nearest-Neighbor Interactions 9.7.3 Burst Synchronization 9.7.4 Rhythmic Population Oscillations in the Hippocampus 9.7.5 Feature Integration
Mean-Field Model of Cortical OscillationsMean-Field Model of Cortical Oscillations
How limit cycle oscillations may arise in a single cortical column in response to external stimuli?
Delay Connections and Nearest-Neighbor Delay Connections and Nearest-Neighbor InteractionsInteractions Delay connections in a simplified oscillator unit obeying the
followings.
Results When the time delays are either too small or too large, a system of
two coupled units will relax to a stable fixed point. There is a broad range of delays in the vicinity of 4 to 5 ms for
which the system will exhibit stable limit cycle behavior. Desynchronization was promoted by adding a second set of delay
connections operating between next nearest neighbors.
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Delay
Damping Constant Noise inputs
Burst SynchronizationBurst Synchronization
Bush & Douglas A network composed of excitatory pyramidal and inhibitory basket
(smooth) neurons. Showing a rapid onset of synchronous bursting with randomly varying
interburst intervals. Koch & Schuster
Simplified Bush & Douglas Model One containing all-to-all excitatory binary (McCulloch-Pitts) neurons A single global inhibitor.
Generating burst synchronization without frequency locking The neural circuitry functions as a coincidence detector Inhibition improves frequency locking and determines the frequency
Rhythmic Population Oscillations in the Rhythmic Population Oscillations in the HippocampusHippocampus Hippocampus exhibits several different types of rhythmicity
and has a number of possibly redundant mechanisms for inducing collective responses. Hippocampal cells extend out widely arborizing axon collaterals those
provide the connectivity to generate recurrent excitation. GABAergic interneurons are present.
Inhibitory postsynaptic potentials (IPSP) are consistent with the timing required for recurrent inhibition.
Cells are capable of repetitive bursting The membrane potential of single pyramidal cells can oscillate in the
4~10 Hz range. Oscillatory cells in the entorhinal cortex projecting to hippocampal
neurons can also drive cells into 4~10 Hz oscillations. The 40-Hz oscillations
are a collective behavior of the network of inhibitory interneurons in the hippocampus. Mutual inhibition plays a key role for this.
Are from the intrinsic 40-Hz oscillatory interneurons.9(C) 2009, SNU Biointelligence Lab, http://bi.snu.ac.kr/
Computational studies for the characteristics of hippocampal rhythmicity. Traub et al.
200 excitatory neurons in a two-dimensional array 10 inhibitory neurons uniformly distributed across the array.
– Two types: fast inhibition, slow one When fast inhibition is present the bursting neurons self-organize
into clusters of synchronously firing cells. When fast inhibition is blocked, most of the cells in the population
Assembly coding and MRF-based integration-by-labeling are self-organizing processes that reinforce and improve the integration of features from one iteration to the next and are robust against noise.
Visual cortical areas were built from feature selective cells arranged topographically into cortical columns.
Assembly coding has been identified with gamma-band rhythmicity.