Network recruitment to coherent oscillations in a hippocampal computer model

Abstract

Stacey WC, Krieger A, Litt B. Network recruitment to coherent oscillations in a hippocampal computer model. J Neurophysiol 105: 1464-1481, 2011. First published January 27, 2011 doi:10.1152/jn.00643.2010.-Coherent neural oscillations represent transient synchronization of local neuronal populations in both normal and pathological brain activity. These oscillations occur at or above gamma frequencies (Ͼ30 Hz) and often are propagated to neighboring tissue under circumstances that are both normal and abnormal, such as gamma binding or seizures. The mechanisms that generate and propagate these oscillations are poorly understood. In the present study we demonstrate, via a detailed computational model, a mechanism whereby physiological noise and coupling initiate oscillations and then recruit neighboring tissue, in a manner well described by a combination of stochastic resonance and coherence resonance. We develop a novel statistical method to quantify recruitment using several measures of network synchrony. This measurement demonstrates that oscillations spread via preexisting network connections such as interneuronal connections, recurrent synapses, and gap junctions, provided that neighboring cells also receive sufficient inputs in the form of random synaptic noise. "Epileptic" high-frequency oscillations (HFOs), produced by pathologies such as increased synaptic activity and recurrent connections, were superior at recruiting neighboring tissue. "Normal" HFOs, associated with fast firing of inhibitory cells and sparse pyramidal cell firing, tended to suppress surrounding cells and showed very limited ability to recruit. These findings point to synaptic noise and physiological coupling as important targets for understanding the generation and propagation of both normal and pathological HFOs, suggesting potential new diagnostic and therapeutic approaches to human disorders such as epilepsy. epilepsy; synchrony; noise COHERENT OSCILLATIONS in the brain are present in a variety of conditions and span a broad range of frequencies and brain regions. These oscillations are often characterized on the basis of their frequency.

Update on the mechanisms and roles of high‐frequency oscillations in seizures and epileptic disorders

“…12 Other studies have described how physiological HFOs could transition to epileptic HFOs with pathologies such as loss of inhibition, or increased coupling from gap junctions, or recurrent synapses and increased synaptic activity. 24; 25 A recent detailed model, designed to mimic how both pyramidal action potentials and inhibitory postsynaptic potentials (IPSP) appear on an intracranial recording electrode, demonstrated several important predictions about HFOs. 26 First, at frequencies below 250 Hz, both epileptic and physiological processes can produce HFOs with identical peak frequencies, suggesting that they cannot be distinguished by frequency alone.…”

Emergence of Narrowband High Frequency Oscillations from Asynchronous, Uncoupled Neural Firing

“…We previously used a biophysical model to explore the underlying mechanisms of physiological and pathological HFOs 23 and describe how they can recruit neighboring tissue. 24 We then modified that model to be able to generate an LFP signal, in order to distinguish the difference between AP-generated and PSP-generated HFOs. 25 We used that model to explore the basic parameters necessary to produce HFOs, and surprisingly found that narrowband ripple oscillations may be generated by completely asynchronous , stochastic spiking of pyramidal cells, and that fast ripples transiently emerge from this asynchronous activity.…”

Nonictal EEG biomarkers for diagnosis and treatment

“…Microcircuit alterations, such as deficits in astrocyte‐mediated glutamate and γ‐aminobutyric acid (GABA) regulation could contribute to neuronal hyperexcitability found in epileptogenic tissue . Computer models that combine reduced inhibition, increased “synaptic noise,” which could derive from abnormal neuronal spike firing, and synaptic reorganization can generate pHFOs …”

“…65,66 Computer models that combine reduced inhibition, increased "synaptic noise," which could derive from abnormal neuronal spike firing, and synaptic reorganization can generate pHFOs. 67…”