Abstract
Despite ongoing advancements in our understanding of the local single-cellular and network-level activity of neuronal populations in the human brain, extraordinarily little is known about their ‘intermediate’ microscale local circuit dynamics. Here, we utilized ultrahigh density microelectrode arrays and a rare opportunity to perform intracranial recordings across multiple cortical areas in human participants to discover three distinct classes of cortical activity that are not locked to ongoing natural brain rhythmic activity. The first included fast waveforms similar to extracellular single unit activity. The other two types were discrete events with slower waveform dynamics and were found preferentially in upper layers of the grey matter. They were also observed in rodents, non-human primates, and semi-chronic recordings in humans via laminar and Utah array microelectrodes. The rates of all three events were selectively modulated by auditory and electrical stimuli, pharmacological manipulation, and cold saline application and had small causal co-occurrences. These results suggest that with the proper combination of high resolution microelectrodes and analytic techniques it is possible to capture neuronal dynamics that lay between somatic action potentials and aggregate population activity and that understanding these intermediate microscale dynamics may reveal important details of the full circuit behavior in human cognition.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
To address questions of regarding these microscale events on microelectrodes, we demonstrate we can find these events in laminar microelectrode array (N=9) and Utah array recordings (N=8) from semi-chronic human studies. For this reason, we have changed the title of the original submission as well as the writing to reflect a focus on these events detected on or near the cortical surface of the brain. We have added several more coauthors to the manuscript to reflect their hard work in gathering these data. In addition, we have included further spectral analyses in the Supplemental files and included more gathered data and further analyses.