Columnar localization and laminar origin of cortical surface electrical potentials

Abstract

Electrocorticography (ECoG) methodologically bridges basic neuroscience and understanding of human brains in health and disease. However, the localization of ECoG signals across the surface of the brain and the spatial distribution of their generating neuronal sources are poorly understood. To address this gap, we recorded from rat auditory cortex using customized ECoG, and simulated cortical surface electrical potentials with a full-scale, biophysically detailed cortical column model. Experimentally, ECoG-derived auditory representations were tonotopically organized and signals were anisotropically localized to [≤]{+/-}200 m, i.e., a single cortical column. Biophysical simulations reproduce experimental findings, and indicate that neurons in cortical layers V and VI contribute [~]85% of evoked high-gamma signal recorded at the surface. Cell number and synchronicity were the primary biophysical properties determining laminar contributions to evoked ECoG signals, while distance was only a minimal factor. Thus, evoked ECoG signals primarily originate from neurons in the infragranular layers of a single cortical column. In BriefBaratham et al., investigated the localization and origins of sensory evoked ECoG responses. They experimentally found that ECoG responses were anisotropically localized [≤]{+/-}200 m, i.e., a single cortical column. Biophysically detailed simulations revealed that neurons in layers V &VI were the primary sources of evoked ECoG responses, in contrast to common thinking. HighlightsEvoked ECoG signals are localized on the surface to a cortical column. Neurons in cortical layers V and VI constitute the vast majority of the signal recorded at the surface. Different laminar contributions to ECoG signal are driven by cell density and synchronicity.