Causal relationships between frequency bands of extracellular signals in visual cortex revealed by an information theoretic analysisReport as inadecuate

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Journal of Computational Neuroscience

, Volume 29, Issue 3, pp 547–566

First Online: 16 April 2010Received: 20 August 2009Revised: 27 January 2010Accepted: 25 March 2010


Characterizing how different cortical rhythms interact and how their interaction changes with sensory stimulation is important to gather insights into how these rhythms are generated and what sensory function they may play. Concepts from information theory, such as Transfer Entropy TE, offer principled ways to quantify the amount of causation between different frequency bands of the signal recorded from extracellular electrodes; yet these techniques are hard to apply to real data. To address the above issues, in this study we develop a method to compute fast and reliably the amount of TE from experimental time series of extracellular potentials. The method consisted in adapting efficiently the calculation of TE to analog signals and in providing appropriate sampling bias corrections. We then used this method to quantify the strength and significance of causal interaction between frequency bands of field potentials and spikes recorded from primary visual cortex of anaesthetized macaques, both during spontaneous activity and during binocular presentation of naturalistic color movies. Causal interactions between different frequency bands were prominent when considering the signals at a fine ms temporal resolution, and happened with a very short ms-scale delay. The interactions were much less prominent and significant at coarser temporal resolutions. At high temporal resolution, we found strong bidirectional causal interactions between gamma-band 40–100 Hz and slower field potentials when considering signals recorded within a distance of 2 mm. The interactions involving gamma bands signals were stronger during movie presentation than in absence of stimuli, suggesting a strong role of the gamma cycle in processing naturalistic stimuli. Moreover, the phase of gamma oscillations was playing a stronger role than their amplitude in increasing causations with slower field potentials and spikes during stimulation. The dominant direction of causality was mainly found in the direction from MUA or gamma frequency band signals to lower frequency signals, suggesting that hierarchical correlations between lower and higher frequency cortical rhythms are originated by the faster rhythms.

KeywordsLocal field potentials Transfer Entropy TE Information theory Action Editor: Mark van Rossum

Electronic supplementary material The online version of this article doi:10.1007-s10827-010-0236-5 contains supplementary material, which is available to authorized users.

This research was supported by the Max Planck Society, by the BMI Project of the Italian Institute of Technology and by the San Paolo Foundation.

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Author: Michel Besserve - Bernhard Schölkopf - Nikos K. Logothetis - Stefano Panzeri



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