arXiv subjects

Michal Zochowski

Publications and source records attributed to Michal Zochowski.

5 recordsLinked to original sources

arXiv2018

Criticality, stability, competition, and consolidation of new representations in brain networks

The brain forms and stores distributed representations from sparse external input that compete for neuronal resources with already stored memory traces. It is unclear what dynamical properties of neural systems allow formation and subsequent consolidation of new, distributed memory representations under these conditions. Here we use analytical, computational, and experimental approaches to show that a dynamical regime near a phase-transition in neuronal network activity (i.e. criticality) may play an important role in this process. Our results reveal that near-critical dynamics are necessary to stabilize and store new sparsely driven representations when they compete with native network states.

q-bio.NC↗

arXiv2009

Network structure determines patterns of network reorganization during adult neurogenesis

New cells are generated throughout life and integrate into the hippocampus via the process of adult neurogenesis. Epileptogenic brain injury induces many structural changes in the hippocampus, including the death of interneurons and altered connectivity patterns. The pathological neurogenic niche is associated with aberrant neurogenesis, though the role of the network-level changes in development of epilepsy is not well understood. In this paper, we use computational simulations to investigate the effect of network environment on structural and functional outcomes of neurogenesis. We find that small-world networks with external stimulus are able to be augmented by activity-seeking neurons in a manner that enhances activity at the stimulated sites without altering the network as a whole. However, when inhibition is decreased or connectivity patterns are changed, new cells are both less responsive to stimulus and the new cells are more likely to drive the network into bursting dynamics. Our results suggest that network-level changes caused by epileptogenic injury can create an environment where neurogenic reorganization can induce or intensify epileptic dynamics and abnormal integration of new cells.

q-bio.NC↗

arXiv2006

Structural network heterogeneities and network dynamics: a possible dynamical mechanism for hippocampal memory reactivation

The hippocampus has the capacity for reactivating recently acquired memories [1-3] and it is hypothesized that one of the functions of sleep reactivation is the facilitation of consolidation of novel memory traces [4-11]. The dynamic and network processes underlying such a reactivation remain, however, unknown. We show that such a reactivation characterized by local, self-sustained activity of a network region may be an inherent property of the recurrent excitatory-inhibitory network with a heterogeneous structure. The entry into the reactivation phase is mediated through a physiologically feasible regulation of global excitability and external input sources, while the reactivated component of the network is formed through induced network heterogeneities during learning. We show that structural changes needed for robust reactivation of a given network region are well within known physiological parameters [12,13].

q-bio.NC↗

arXiv2005

Local driving and global interactions in the progression of seizure dynamics

The dynamics underlying epileptic seizures are well understood. We present a novel analysis of seizure-like events (SLEs) in an \textit{ex vivo} whole hippocampus, as well as a modeling study that sheds light on the underlying network dynamics. We show that every SLE can be divided into two phases. During the first, SLE dynamics are driven by the intra-network interaction of a network exhibiting high internal synchrony. The second phase is characterized by lead switching, with the leading region exhibiting low internal synchrony. We show that the second phase dynamics are driven by inter-network feedback among multiple regions of the hippocampus.

physics.bio-ph↗

arXiv2003

Measurement of synchronization properties in systems with different excitation levels

We devised a measure based on the distributions of relative event timings of two coupled units. The measure dynamically evaluates temporal interdependencies between the two coupled units. Using this we show that even in the event of symmetrical coupling, non-identical units (having different control parameters) have small but persistent shifts in their event timings that change dramatically with the relative properties of their internal trajectories. We link that finding with the activity dependent synaptic modification in the brain showing that internally or externally driven excitation levels of the neuron may determine direction of information processing in a network.

nlin.CD↗