Prof. Dr. Marie-Claude Hepp-Reymond

 

Main Goals, Keywords

Functional characterization of motor and premotor cortical hand representations (receptive field, microstimulation, correlation of neuronal activity with grip force, anatomical specialization (immunohistochemistry, histochemistry) and connectivity of the cortical hand regions. Organization of premotor and motor cortex in human subjects and its reorganization in patients (hand, grip force, neuroanatomy, single neuron activity, fMRI).

Group Members

1 professor, 1 postdoctoral fellow, 1 PhD student. Collaborators in the Neuroradiology Department of the University Hospital.

Previous and Current Research

For many years our research has been aimed at the understanding of the central and peripheral control of force in monkey and man, taking the precision grip as an experimental model. Our investigations revealed that many neurons located in the various finger representations in the motor (M1), premotor (PM) and sensory cortex, and in related subcortical regions participate in the control of grip force. Some PM regions present many features similar to those disclosed in M1, and in three discrete regions of the PM cortex task-related and force-correlated activity was found. For a population of PM and M1 neurons context-dependent force coding was revealed. Another ongoing investigation has for goal to define boundaries between M1 and PM cortex and within PM itself, by using staining methods revealing cytochromoxydase (CO), acetylcholinesterase (AChE), calcium binding proteins, some of the GABA_A receptor subunits and neurofilaments in pyramidal neurons (SMI-32). The combination of two or several methods help drawing clearer boundaries between subregions (see Figure). The connectivity between the various hand representations is also investigated. These neuroanatomical data serve as a complement to the functional characterization. A parallel study in human subjects exerting fine-graded grip force under conditions similar to those used in the monkey experiments, is focused on the activity patterns, the coactivation and synchronization of muscles and motor units during the performance of the motor task.

 

Future Projects

We will bring to an end the project on functional and anatomical characteristics of the premotor cortex in the monkey. In parallel, our research will be focused on the collaborative project with Dr. S. Kollias (Neuroradiology Dept.) on the functional organization of the motor and premotor cortex and reorganization in patients with brain lesions.

Techniques and Equipment

The recording of the single neuron activity in trained monkeys includes a complete electrophysiological set-up with computer-driven training and data acquisition systems. The quantitative and statistical analysis is made on a Sun Sparc5 workstation. The fMRI project is performed on a 1.5 Tesla MR imaging system at the Neuroradiology Department of the University Hospital.

Selected Publications

• Yu, N., Estévez, N., Hepp-Reymond, M.C., Kollias, S.S., Riener, R. fMRI assessment of upper extremity related brain activation with an MRI-compatible manipulandum. Int J Comput Assist Radiol Surg. Aug 10 (2010).
  
• Keisker, B., Hepp-Reymond, M.C., Blickenstorfer, A., Kollias, S.S. Differential representation of dynamic and static power grip force in the sensorimotor network. Eur J Neurosci. Apr; 31(8): 1483-91 (2010). Epub 2010 Apr 6.
• Hepp-Reymond, M.C., Chakarov, V., Schulte-Mönting, J., Huethe, F., Kristeva, R. Role of proprioception and vision in handwriting. Brain Res Bull. Aug 14; 79(6): 365-70 (2009). Epub 2009 May 20.

Selected Lectures, Seminars or Colloquia

Einführung in die Neurophysiologie I und II, Kognitive Neurowissenschaften, Neuroinformatics Kolloquium

Funding

NRP 38 "Diseases of the Nervous System"

URL

www.ini.uzh.ch