CELL-TYPE SPECIFIC ORIGINS OF THE EEG SIGNAL

The standard dipole model of EEG generation proposes that the EEG signal at an electrode is the summation of dipoles in the underlying cortical area. These dipoles are generated along the somatodendritic axis of pyramidal neurons perpendicular to the brain’s surface after synaptic transmission. However, this model does not describe cell-type specific contributions to the EEG signal. Understanding this relationship could facilitate translation of cell-type specific effects, such as the decorrelation effect of antipsychotics in layer V intratelencephalic (IT) cells, and enable investigation of these effects in humans. To study this interrelation, concurrent widefield calcium imaging and EEG recordings were performed in mice expressing calcium indicators in excitatory neurons of layer II/III, layer V IT cells, layer V extratelencephalic (ET) cells, as well as parvalbumin (PV)-positive interneurons. Mice were head-fixed under a widefield imaging setup and faced a toroidal screen on which short standing gratings were projected. Skull thinning surgery and the use of transparent EEG probes enabled optical measurement of neuronal activity. Gratings were presented to both awake and anesthetized mice. Correlations between widefield calcium signals and EEG power showed the increases in EEG bands above 10 Hz for excitatory neurons in layer II/III, layer V IT, and layer V ET neurons in anesthetized compared to awake mice. In contrast, a decrease in those higher frequency bands was found in PV neurons. These results suggest that different cell types contribute distinctly to the EEG signal and that these contributions are brain-state dependent.