P 16. Modulating emerging cortical activity with electric fields in brain slices

Introduction During slow-wave-sleep (SWS) or deep anesthesia the EEG activity displays low frequency ( Objectives Our objective has been to quantify the modulation of the emergent activity and network entrainment that we could achieve by exposing the cortical slices to a varying electric field. Material and methods Slow oscillations were obtained from visual and prefrontal cortex slices as described in (Sanchez-Vives, 2012). A uniform electric field was generated by passing current between two parallel AgCl-coated silver wires placed in parallel to the cortical layers. The intensity of the electric field was varied on time. Extracellular recordings of field potentials were obtained using tungsten electrodes or multielectrode arrays. Results The application of a constant current through the stimulating electrodes generates an electric field parallel to the apical-dendritic axis of pyramidal cortex neurons which is capable of depolarize or hyperpolarize the neuron's resting membrane potentials. We find that electric fields of the appropriate orientation are indeed powerful modulators of the emergent activity patterns through excitability changes, in agreement with other authors (Frohlich and McCormick, 2010). Furthermore, we obtain as well a systematic modulation of higher frequencies of oscillations within the beta and gamma ranges. Conclusions These encouraging results suggest that proper manipulation of the electric fields can achieve highly specific spatio-temporal control of the activity. This provides a valuable testbed for the study of cortical stimulation of the intervention in different models of neurological alterations. Funded by BFU2011-27094 (Spain).