Pathway formation and dynamical transitions by neuronal traveling waves with synaptic plasticity

Kendall J. Butler

doi:10.17918/00010983

Although traveling waves are consistently observed throughout the brain, no definitive conclusion has emerged regarding their precise function or purpose. However, the observation of these waves in regions related to learning, memory, and sensory processing has implied that synaptic plasticity may play an important role. In order to investigate this role, our research specifically focuses on the effects of synaptic plasticity on neuronal traveling waves. The lack of experimental results has led others to carry out computational studies to investigate neuronal traveling waves, but these have not been sufficient to determine their direct interactions with plasticity. In order to computationally explore the effects of traveling waves with plasticity, we create a model quasi-2D network of Izhikevich Model neurons, exponential distance-dependent connection probabilities, and synaptic time delays. With our model, we first apply synaptic plasticity in the form of Spike-Timing Dependent Plasticity (STDP). Our results show that with STDP, traveling waves form preferred propagation pathways and act as a mechanism of large-scale competition between initially available pathways. These results inform our understanding of the functions neuronal traveling waves may have, considering their coincidence with synaptic plasticity in the brain. Second, we remove STDP and directly adjust network parameters in order to elucidate a dynamical phase space aimed at delineating the differences between experimentally observed circular and spiral waveforms. With independent parameters adjusting the rate of membrane recovery and the scale of distance-dependent time delays, we reveal separate dynamical regions of the phase space using the temporal longevity of induced traveling waves and the mean normalized curl of wave propagation. We find that the scale of distance-dependent delays in particular has a meaningful effect in both regions of the phase space. Considering the possibility that plasticity in the brain could modulate the region of phase space explored by traveling waves, we introduce a biologically plausible model for this hypothesized process that changes signal delays called delay-STDP. Three possible forms of delay-STDP that could be responsible for these transitions include monotonically increasing delays, monotonically decreasing delays and bidirectional delay changes, each showing diverse effects on the population firing rates, temporal longevity, and propagation curl of the induced waves. In addition, we find that the bidirectional delay-STDP may support or enhance the effects of regular STDP. Our simple model of delay-STDP introduces testable conclusions for the continued study of delay plasticity, which is not yet well defined. With continued research into the dynamics and complex interactions of traveling waves with neuronal systems, we will approach a fuller understanding of this phenomenon as well as its function in the brain.

Pathway formation and dynamical transitions by neuronal traveling waves with synaptic plasticity

Files and links (1)

Abstract

Metrics

Details

Pathway formation and dynamical transitions by neuronal traveling waves with synaptic plasticity

Files and links (1)

Abstract

Metrics

Details

Drexel University Social media