[Phys-seminars] 2017-06-21 Condensed Matter Theory Seminar

smoshe smoshe at bgu.ac.il
Sat Jun 10 17:40:49 IDT 2017


Condensed Matter Theory Seminar

 DATE: 21-06-17

 TIME: 13:30

 PLACE: Physics building (#54) room 207

TITLE: 
Emergence of oscillatory activity via spike timing dependent plasticity

SPEAKER: 
Sarit Nagar, Ben Gurion University

ABSTRACT/COMMENTS: 
Neuronal oscillatory activity has been reported in relation to a wide range of cognitive processes. In certain cases changes in the oscillatory activity have been related to pathological states. Although the specific role of these oscillations has yet to be determined, it is clear that neuronal oscillations are abundant in the central nervous system. These observations raise the question of the origin of these oscillations: are the mechanisms responsible for generation and stabilization of these oscillations genetically hard-wired or can they be acquired via a learning process? Here we focus on spike timing dependent plasticity (STDP) and ask: Can oscillatory activity emerge in a neuronal network via an unsupervised learning process of STDP dynamics? If so, how and what features of the STDP learning rule govern and stabilize the resultant oscillatory activity? To this end we studied the STDP dynamics of the effective coupling between two competing neuronal populations with re
 ciprocal inhibitory connections. To analyze the system it is convenient to study the phase-diagram that depicts the possible dynamical states of the network as a function of the effective inhibitory couplings. We find that this phase diagram displays a rich repertoire of possible dynamical behaviors including regions of different fixed point solutions, bi-stability and a region in which the system exhibits oscillatory activity. STDP introduces dynamics for the inhibitory couplings themselves; hence, induces a flow on the phase-diagram. We developed mean-field-Fokker-Planck theory for the stochastic dynamics of the synaptic couplings in the limit of slow learning. In this limit we studied the STDP- induced flow on the phase diagram and investigated the conditions for the flow to converge to an oscillatory state of the neuronal network. We characterized how the features of the STDP rule govern and stabilize these oscillations.


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