Neural dynamics in Parkinsonian brain: The boundary between synchronized and nonsynchronized dynamics

Abstract

Synchronous oscillatory dynamics is frequently observed in the human brain. We analyze the fine temporal structure of phase-locking in a realistic network model and match it with the experimental data from parkinsonian patients. We show that the experimentally observed intermittent synchrony can be generated just by moderately increased coupling strength in the basal ganglia circuits due to the lack of dopamine. Comparison of the experimental and modeling data suggest that brain activity in Parkinson’s disease resides in the large boundary region between synchronized and nonsynchronized dynamics. Being on the edge of synchrony may allow for easy formation of transient neuronal assemblies.

Effects of Electrical and Optogenetic Deep Brain Stimulation on Synchronized Oscillatory Activity in Parkinsonian Basal Ganglia

“…From the dynamical systems standpoint, this model's phase space is similar to the one reconstructed from experiments not only at the vicinity of synchronization manifold, but at the periphery as well [14,18]. The model network has two arrays of neurons: ten GPe neurons and ten STN neurons (see Fig.…”

“…We adopt a conductance-based modeling of [14], which in Effects of electrical and optogenetic deep brain stimulation on synchronized oscillatory activity in Parkinsonian basal ganglia Shivakeshavan Ratnadurai-Giridharan, Chung C. Cheung, and Leonid L. Rubchinsky D turn was based on [15] and considers STN and external Globus Pallidus (GPe). While this model is limited in several ways (for example, it excludes several brain areas, relevant for parkinsonian pathophysiology), it is based on the known anatomical and physiological data and incorporates rhythmicity mechanisms resulting from the recurrent excitation and inhibition in STN-GPe circuits [16].…”

“…The membrane potential obeys . All the equations for membrane and synaptic currents and network parameters are available in [14]. Stimulation (described below) is applied to STN.…”

“…The network model used here has been studied in [14] without stimulation within the two-dimensional parameter space of (g syn , I app ), where g syn is the strength of the synaptic connections from GPe to STN and I app is the constant current applied to GPe to model average impact of striatopallidal inhibition. These parameters are thought to be modulated by dopamine, which degenerates in PD.…”

“…These parameters are thought to be modulated by dopamine, which degenerates in PD. Larger values of g syn and smaller values of I app correspond to a low-dopamine state [14].…”