Non-invasive Assessment of Superficial and Deep Layer Circuits in Human Motor Cortex
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Circuits distributed across layers in the motor cortex are considered to have a pivotal role in voluntary movement control. Studies that applied innovative methods in animals in recent years have generated significant insights into functions of different circuits, and into dysfunctions in the diseased state. However, what has been possible in animal research was so far impossible to achieve in human motor control studies, and thus the functions of human motor circuits remain largely unresolved.
„A necessity for progress in human neurophysiology is certainly the improvement of methods to assess neural activity” says Christian Leukel, PI of the research team in Freiburg. “A reasonable approach for development is to search for key findings from animal experiments. Some of these findings can stimulate new ideas for methods in humans, on the basis of possibilities and limitations of existing non-invasive tools”, he adds.
Indeed, this was the strategy of the international collaborating teams. The research group from Newcastle lead by Prof. Stuart Baker first conducted brain slice and in vivo experiments on monkey motor cortex. These single cell recordings revealed a small temporal shift in the activation of deep layer output cells following stimulation of deep versus superficial layers. In subsequent experiments the research group from Freiburg used this temporal information to elaborate a non-invasive electrophysiological method in the human motor cortex. This method is derived from a known conditioning technique involving transcranial magnetic stimulation (TMS) and peripheral nerve stimulation (PNS). Modifications in the application and data processing allowed the research group to assess layer-specific activity modulations during a complex cognitive motor task.
“We expect that the proposed method will open up new avenues for research into cognitive, motor and sensory processing in humans, both in healthy and in pathological states where changes in layer-specific cortical circuits have been implicated, such as autism and cortical dysplasia.”, concludes Alexander Kurz, PhD student at the Bernstein Center Freiburg and the Department of Sport Science Freiburg.
Transcranial magnetic stimulation
A non-invasive brain stimulation technique which is widely used to probe function and connectivity of brain areas in humans.
Figure Legend
Schematic illustration of the non-invasive electrophysiological technique involving transcranial magnetic stimulation (TMS) and peripheral nerve stimulation (PNS). Figure: Alexander Kurz
Original Publication
Kurz, A., Xu, W., Wiegel, P., Leukel, C., and Baker, S. (2019). Non-invasive assessment of superficial and deep layer circuits in human motor cortex. J Physiol. https://doi.org/10.1113/JP277849
Contact
Alexander Kurz
University of Freiburg
Department of Sport Science &
Bernstein Center Freiburg
Hansastraße 9a
79104 Freiburg, Germany
E-mail: alexander.kurz@sport.uni-freiburg.de