Traveling Waves and the Processing of Weakly Tuned Inputs in a Cortical Network Module

1. J Comput Neurosci. 1997 Jan;4(1):57-77. doi: 10.1023/a:1008816611284.

Traveling waves and the processing of weakly tuned inputs in a cortical network
module.

Ben-Yishai R(1), Hansel D, Sompolinsky H.

Author information:
(1)Racah Institute of Physics and Center for Neural Computation, Hebrew
University, Jerusalem, Israel.

Recent studies have shown that local cortical feedback can have an important
effect on the response of neurons in primary visual cortex to the orientation of
visual stimuli. In this work, we study the role of the cortical feedback in
shaping the spatiotemporal patterns of activity in cortex. Two questions are
addressed: one, what are the limitations on the ability of cortical neurons to
lock their activity to rotating oriented stimuli within a single receptive
field? Two, can the local architecture of visual cortex lead to the generation
of spontaneous traveling pulses of activity? We study these issues analytically
by a population-dynamic model of a hypercolumn in visual cortex. The order
parameter that describes the macroscopic behavior of the network is the
time-dependent population vector of the network. We first study the network
dynamics under the influence of a weakly tuned input that slowly rotates within
the receptive field. We show that if the cortical interactions have strong
spatial modulation, the network generates a sharply tuned activity profile that
propagates across the hypercolumn in a path that is completely locked to the
stimulus rotation. The resultant rotating population vector maintains a constant
angular lag relative to the stimulus, the magnitude of which grows with the
stimulus rotation frequency. Beyond a critical frequency the population vector
does not lock to the stimulus but executes a queasi-periodic motion with an
average frequency that is smaller than that of the stimulus. In the second part
we consider the stable intrinsic state of the cortex under the influence of
isotropic stimulation. We show that if the local inhibitory feedback is
sufficiently strong, the network does not settle into a stationary state but
develops spontaneous traveling pulses of activity. Unlike recent models of wave
propagation in cortical networks, the connectivity pattern in our model is
spatially symmetric, hence the direction of propagation of these waves is
arbitrary. The interaction of these waves with an external-oriented stimulus is
studied. It is shown that the system can lock to a weakly tuned rotating
stimulus if the stimulus frequency is close to the frequency of the intrinsic
wave.

DOI: 10.1023/a:1008816611284
PMID: 9046452 [Indexed for MEDLINE]

Auteurs Bordeaux Neurocampus