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Phase-coupled oscillator models can predict hippocampal inhibitory synaptic connections

Authors

  • F. K. Skinner,

    1. 1 Toronto Western Research Institute, University Health Network, 399 Bathurst Street, MP12-303, Toronto, Ontario, Canada Departments of 2Medicine (Neurology) and 3Physiology, University of Toronto, Toronto, Ontario, Canada 4Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
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  • 1,2,3,4 C. Wu,

    1. 1 Toronto Western Research Institute, University Health Network, 399 Bathurst Street, MP12-303, Toronto, Ontario, Canada Departments of 2Medicine (Neurology) and 3Physiology, University of Toronto, Toronto, Ontario, Canada 4Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
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  • and 1 L. Zhang 1,2

    1. 1 Toronto Western Research Institute, University Health Network, 399 Bathurst Street, MP12-303, Toronto, Ontario, Canada Departments of 2Medicine (Neurology) and 3Physiology, University of Toronto, Toronto, Ontario, Canada 4Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
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: Dr F. K. Skinner, at 1Toronto Western Research Institute, as above.
E-mail:fskinner@uhnres.utoronto.ca

Abstract

What factors are responsible for propagating electrical activity in the hippocampus? Using an intact, isolated hippocampus preparation, it is possible to observe spontaneous delta (≤ 4 Hz) waves of rhythmic field potentials. These rhythmic potentials are inhibitory in nature, mediated by GABAergic inhibitory potentials originating from a population of principal neurons. They start in the ventro-temporal region and move longitudinally towards the dorso-septal region with a phase lag of ≈ 10% between the extracellular recordings. We use the mathematical framework of phase-coupled oscillators (PCO) to gain some insight into the underlying network system. A chain of 15 nearest-neighbour bidirectionally coupled PCOs is used where each oscillator refers to a segment of the CA1 region of the hippocampus that can generate these slow field potentials. We find that ventro-dorsal delta waves exist if there is a dominance in coupling strength in one direction. Without a one-way coupling dominance, ventro-dorsal waves can still exist, but then the coupling strengths need to be much larger. The relationship between entrained and intrinsic frequencies and the variation of propagation speeds along the longitudinal axis can be used to determine which case applies. Currently available experimental data supports one of the cases, predicting that there is a stronger ventral to dorsal inhibitory effect.

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