Conferencia Invitada. Information transmission and the neural code(Complexity, epileptic seizures, LFP energy oscillations and spikes correlations)

FERNANDO MONTANI

Viña del Mar (Chile)

Workshop; Twelfth International Workshop on Instabilities and Nonequilibrium Structures; 2009

We investigate the internal dynamic of LFPs signals obtained from multisite extracellular microelectrode recordings of rat visual cortex. In order to do it so, we perform Brandt and Pompe’s permutation entropy estimations to take into account the temporal structure of the signal and its causal information. Our approach is particularly useful to detect the presence of internal dynamical noise on the basis of counting ordinal patterns included through the probability distribution in the entropy estimations. This allows us first to identify the intrinsic embedded dimensionality of the LFP’s energy spectra considering time intervals between consecutives UP and DOWN switching at different frequency bands. Second, characterize low frequency band (1-10Hz) as an ‘order state’ and the higher band as ‘disorder state’. Finally, we perform an Information theoretical approach to answer the question by how much does observing this response sequence reduce the uncertainty about when the start of the LFP response sequence occurs. Our findings show that the low frequency bands play a crucial role in the rhythmic activity pattern in the brain, and in the processing of sensory information. However, it is important to point out that bi-stable LFP are also prevalent and informative in the gamma frequency band of the energy spectra