126 research outputs found
Fine temporal structure of neural synchronization
poster abstractWhile neural synchronization is widely observed in neuroscience, neural oscillations are rarely in perfect synchrony and go in and out of phase in time. Since this synchrony is not perfect, the same synchrony strength may be achieved with markedly different temporal patterns of activity (roughly speaking oscillations may go out of the phase-locked state for many short episodes or few long episodes). Provided that there is some average level of phase-locking is present, one can follow oscillations from cycle to cycle and to observe if the phase difference is close to the preferred phase lag or not.
Here we study neural oscillations recorded by EEG in alpha and beta frequency bands in a large sample of healthy human subjects at rest and during the execution of a simple motor task. While the phase-locking strength depends on many factors, dynamics of synchrony has a very specific temporal pattern: synchronous states are interrupted by frequent, but short desynchronization episodes. The probability for a desynchronization episode to occur decreased with its duration. The modes and medians of distributions of desynchronization durations were always just one cycle of oscillations. Similar temporal patterning of synchrony in different brain areas in different states may suggest that i) this type of patterning is a generic phenomenon in the brain, ii) it may have some functional advantages for oscillating neural networks receiving, processing, and transmitting information, iii) it may be grounded in some general properties of neuronal networks calling for the development of appropriate nonlinear dynamical theory. To further investigate these conjectures we numerically studied a system of coupled simple neuronal models (of Morris-Lecar type) and showed that coupled neural oscillators exhibiting short desynchronizations require smaller values of synaptic connections between them of weaker common synaptic input to induce specified levels of synchrony strength than oscillators of the same frequency exhibiting more prolong desynchronizations. The results may suggests that whenever a (partially) synchronous cell assembly must be formed to facilitate some function, short desynchronization dynamics may allow for efficient formation and break-up of such an assembly
Phase-matching of multiple-cavity detectors for dark matter axion search
Conventional axion dark matter search experiments employ cylindrical
microwave cavities immersed in a solenoidal magnetic field. Exploring higher
frequency regions requires smaller size cavities as the TM010 resonant
frequencies scale inversely with cavity radius. One intuitive way to make
efficient use of a given magnet volume, and thereby to increase the
experimental sensitivity, is to bundle multiple cavities together and combine
their individual outputs ensuring phase-matching of the coherent axion signal.
We perform an extensive study for realistic design of a phase-matching
mechanism for multiple-cavity systems and demonstrate its experimental
feasibility using a double-cavity system.Comment: 5 pages, 2 figures, 1 tabl
Concept of multiple-cell cavity for axion dark matter search
In cavity-based axion dark matter search experiments exploring high mass
regions, multiple-cavity design is considered to increase the detection volume
within a given magnet bore. We introduce a new idea, referred to as
multiple-cell cavity, which provides various benefits including a larger
detection volume, simpler experimental setup, and easier phase-matching
mechanism. We present the characteristics of this concept and demonstrate the
experimental feasibility with an example of a double-cell cavity.Comment: 8 pages, 11 figure
Mathematical model of subthalamic nucleus neuron - characteristic activity patterns and bifurcation analysis
The subthalamic nucleus (STN) has an important role in the pathophysiology of
the basal ganglia in Parkinson's disease. The ability of STN cells to generate
bursting rhythms under either transient or sustained hyperpolarization may
underlie the excessively synchronous beta rhythms observed in Parkinson's
disease. In this study, we developed a conductance-based single compartment
model of an STN neuron, which is able to generate characteristic activity
patterns observed in experiments including hyperpolarization-induced bursts and
post-inhibitory rebound bursts. This study focused on the role of three
currents in rhythm generation: T-type calcium (CaT) current, L-type calcium
(CaL) current, and hyperpolarization-activated cyclic nucleotide-gated (HCN)
current. To investigate the effects of these currents in rhythm generation, we
performed a bifurcation analysis using slow variables in these currents.
Bifurcation analysis showed that the HCN current promotes single-spike activity
patterns rather than bursting in agreement with experimental results. It also
showed that the CaT current is necessary for characteristic bursting activity
patterns. In particular, the CaT current enables STN neurons to generate these
activity patterns under hyperpolarizing stimuli. The CaL current enriches and
reinforces these characteristic activity patterns. In hyperpolarization-induced
bursts or post-inhibitory rebound bursts, the CaL current allows STN neurons to
generate long bursting patterns. Thus, bifurcation analysis explained the
synergistic interaction of the CaT and CaL currents, which enables STN neurons
to respond to hyperpolarizing stimuli in a salient way. The results of this
study implicate the importance of CaT and CaL currents in the pathophysiology
of the basal ganglia in Parkinson's disease
- …