Local Field Potentials (LFPs) reflect subthreshold integrative processes that complement spike train measures. However, little is yet know about the differences and complementarity in the way LFPs and spikes encode rich naturalistic sensory stimuli. To address this issue, my collaborator Nikos Logothetis and his group recorded LFPs and spikes from primate V1 while the animal was shownbinocularly a colour Hollywood movie. We then used Information theory to determine which frequencies of LFPs carry information which is complementary or similar to that of spikes. We found that the power of low frequency (< 8 Hz) LFPs carried information about the movie which was independent from that carried by spikes, whereas gamma-range LFPs were informative but redundant with spikes. Further, we found that the phase of the informative low frequency LFPs was very reliable across trials in correspondence of high spike rates. The phase of the LFP oscillation at which spikes were fired conveyed significantly more information about the movie than that carried by spike counts. The extra information available in the phase of firing was crucial for the disambiguation between stimuli eliciting spike rates of similar magnitude. Taken together, these results suggest that a potential role of low frequency oscillations in cortex is to permit the cortical network to transmit more information than that provided by spike counts.
Acknowledgements: This is joint work with with Nikos Logothetis and his group at the MPI Biological Cybernetics Tuebingen. I am also grateful to Cesare Magri, Marcelo Montemurro and Andrei Belistki for their collaboration on this analysis.
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