Efforts to deepen our understanding of the nervous system depends on high resolution sampling of neuronal activity. We leveraged clinically necessary intracranial monitoring performed during surgical resections to record from the cortical surface (N=30) using high spatial resolution, low impedance PEDOT:PSS microelectrodes. We identified three classes of activity. The first included relatively fast repeated waveforms with kinetics similar to, but not perfectly matching, extracellular single unit activity. The other two discrete unitary events with slower waveforms had event frequencies which were selectively modulated by auditory stimuli, electrical stimuli, pharmacological manipulation, and cold saline application. Furthermore, different classes had small but significant causal co-occurrences. We speculate that these different events could reflect axonal action potentials, dendritic calcium spikes, backpropagating action potentials or pre and post-synaptic phenomena, opening the possibility that we can sample information beyond typical extracellular somatic action potentials via high-density, low impedance electrodes on the cortical surface.

Microscale physiological events on the human cortical surface detected with PEDOT:PSS Electrodes