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SUMMARY:Learning sensory and spatial representations from interacting exci
 tatory and inhibitory synaptic plasticity - Henning Sprekeler (University 
 of Cambridge)
DTSTART:20131112T160000Z
DTEND:20131112T170000Z
UID:TALK48867@talks.cam.ac.uk
CONTACT:Guillaume Hennequin
DESCRIPTION:Cortical neurons receive excitatory and inhibitory currents th
 at are correlated both in time and in stimulus selectivity. The mechanisms
  by which this “balance” of excitation and inhibition arises is not fu
 lly understood. In the first part of the talk\, I will present our recent 
 suggestion that Hebbian plasticity of inhibitory synapses (ISP) can establ
 ish a self-organized excitation-inhibition balance in both\nfeedforward 
 “sensory” and recurrent “memory” networks (Vogels et al.\, 2011). 
 In sensory networks\, ISP causes an balance in the stimulus tuning of the 
 excitatory and inhibitory currents. ISP also balances excitatory and inhib
 itory currents in recurrent spiking networks and thereby leads to the self
 -organized formation of an asynchronous irregular state that resembles the
  irregular activity found in cortical\nnetworks.\n\nIn the second part of 
 the talk\, I will present an analysis of the interaction of Hebbian (“ba
 lancing”) ISP with concurrent Hebbian synaptic plasticity of excitatory 
 synapses\, with a focus on feedforward networks. For inhibitory inputs wit
 h a weak stimulus-specificity\, ISP establishes a sliding threshold simila
 r to that of Bienenstock-Cooper-Munro learning rules and thereby allows th
 e self-organized formation of neuronal stimulus-selectivity. For highly st
 imulus-specific inhibition\, the precise excitation-inhibition balance ari
 sing from the inhibitory plasticity acts against the formation of a stimul
 us selectivity in the excitation. In the intermediate regime\, where inhib
 itory inputs have a wider stimulus tuning than their excitatory counterpar
 ts\, the system generates periodic solutions\, which arise from a Turing b
 ifurcation. When the input encodes the animal’s position in a 2-dimensio
 nal environment\, this intermediate regime reliably generates neuronal res
 ponses with a hexagonal grid pattern as observed in grid cells in entorhin
 al cortex.\n\nVogels* TP\, Sprekeler* H\, Zenke F\, Clopath C\, Gerstner H
 . Inhibitory plasticity balances excitation and inhibition in sensory path
 ways and memory networks. Science 334:1569-1573 (2011)\n
LOCATION:Cambridge University Engineering Department\, CBL Rm #438 (http:/
 /learning.eng.cam.ac.uk/Public/Directions)
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