[Comp-neuro] paper announcement

Kilian Koepsell kilian at berkeley.edu
Fri Apr 17 01:51:14 CEST 2009

Dear Colleagues,

We would like to announce two papers we recently published that use  
quantitative approaches to assess the role of oscillations in  
transmitting neural information. The first one describes a method that  
we developed to measure the information carried by oscillating spike  
trains.  The second takes advantage of our new method to show how  
retinal oscillations are able to transmit visual signals downstream.  
Specifically, we show that spike trains of single ganglion cells  
multiplex two streams of information.  In addition to the traditional  
channel that uses rate coding, we discovered a separate channel that  
uses spike timing relative to gamma oscillations to convey  
information.  This second channel could as much as triple the amount  
of information transmitted to the cortex. We hope that these results  
contribute to the previous discussions of the role of oscillations in  
neural coding and look forward to receiving comments and suggestions.

Koepsell K, Sommer FT (2008) Information transmission in oscillatory  
neural activity.
Biol Cybern  99:403–416 http://dx.doi.org/10.1007/s00422-008-0273-6

Periodic neural activity not locked to the stimulus or to motor  
responses is usually ignored. Here, we present new tools for modeling  
and quantifying the information transmission based on periodic neural  
activity that occurs with quasi-random phase relative to the stimulus.  
We propose a model to reproduce characteristic features of oscillatory  
spike trains, such as histograms of inter-spike intervals and phase  
locking of spikes to an oscillatory influence. The proposed model is  
based on an inhomogeneous Gamma process governed by a density function  
that is a product of the usual stimulus-dependent rate and a quasi- 
periodic function. Further, we present an analysis method generalizing  
the direct method (Rieke et al. in Spikes: exploring the neural code.  
MIT Press, Cambridge, 1999; Brenner et al. in Neural Comput 12(7):1531– 
1552, 2000) to assess the information content in such data. We  
demonstrate these tools on recordings from relay cells in the lateral  
geniculate nucleus of the cat.

Koepsell K, Wang X, Vaingankar V, Wei Y, Wang Q, Rathbun DL, Usrey W,  
Hirsch J and Sommer FT (2009)
Retinal oscillations carry visual information to cortex. Front Syst  
Neurosci 3:4 http://dx.doi.org/10.3389/neuro.06.004.2009

Thalamic relay cells fire action potentials that transmit information  
from retina to cortex. The amount of information that spike trains  
encode is usually estimated from the precision of spike timing with  
respect to the stimulus. Sensory input, however, is only one factor  
that influences neural activity. For example, intrinsic dynamics, such  
as oscillations of networks of neurons, also modulate firing pattern.  
Here, we asked if retinal oscillations might help to convey  
information to neurons downstream. Specifically, we made whole-cell  
recordings from relay cells to reveal retinal inputs (EPSPs) and  
thalamic outputs (spikes) and then analyzed these events with  
information theory. Our results show that thalamic spike trains  
operate as two multiplexed channels. One channel, which occupies a low  
frequency band (<30 Hz), is encoded by average firing rate with  
respect to the stimulus and carries information about local changes in  
the visual field over time. The other operates in the gamma frequency  
band (40-80 Hz) and is encoded by spike timing relative to retinal  
oscillations. At times, the second channel conveyed even more  
information than the first. Because retinal oscillations involve  
extensive networks of ganglion cells, it is likely that the second  
channel transmits information about global features of the visual scene.

Kilian Koepsell, PhD
Redwood Center for Theoretical Neuroscience
Helen Wills Neuroscience Institute, UC Berkeley
156 Stanley Hall, MC# 3220 , Berkeley, CA 94720

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