Models of Background Activity in V1

Brendan Murphy

Responses in primary visual cortex are determined both by the visual
stimulus and by ongoing cortical spontaneous activity.  Experiments
using voltage sensitive dyes have found that spontaneous activity
patterns show significant spatial correlations with visually-evoked
orientation maps that decay over times ~80 msec.  Another important
aspect of V1 spontaneous activity is that neurons show large ongoing
voltage fluctuations and high spike time variability.  Model networks
with strong but balanced excitation and inhibition and sparse
connectivity have been shown to have these two characteristics.  These
networks have most commonly been studied with random connectivity.  We
show that a balanced network of integrate-and-fire neurons with
V1-like synaptic connectivity can exhibit spontaneous activity
patterns similar to those observed experimentally.  We also
study a simple linear rate model to better understand the underlying
mechanisms by which these patterns can be generated.