The Bernstein Center for Computational Neuroscience Freiburg

Announcement for the next
BCCN Seminar
PD Dr. Cornelius Schwarz
Hertie-Institut für klinische Hirnforschung
Abteilung für Kognitive Neurologie
Bernhard-Karls-Universität Tübingen

Neuronal Underpinnings of Action and Perception in the Rat's Whisker System

Thursday, May 10th, 2007
Lecture Hall (ground floor)
BCCN building
Hansastraße 9A
79104 Freiburg
My research group has established model system that allows us to study central modulation of tactile processing for active perception in rat’s vibrissal system. Experiments with head-fixed rats trained to whisk toward a moving object and precise whisker tracking allowed us to disentangle sensory and motor aspects of active touch (Hentschke et al., 2006). Recordings in barrel cortex revealed a movement dependent excitatory signal that was correlated with a reduction of the tactile response and its cortical spread. The non-rhythmic nature of the modulatory signal indicated a central origin, a notion confirmed by its intactness and its continued modulatory role after deafferentation. We have found first evidence that the movement dependent signal originates in vibrissal motor cortex which is upstream of the presumed rhythm generating circuits in the brainstem. We discovered a sub-region of vibrissal motor cortex (tagged RW for ‘rhythmic whisking’) that, indeed, generates natural-like rhythmic whisking at frequencies around 7 Hz when electrically stimulated with long stimulus trains at high frequencies (Haiss et al., 2005). Unit recordings within RW during self-initiated whisker movements confirm the non-rhythmic nature of spike activity during rhythmic whisking. We are currently focussing on the perceptual level to find out how active movement modulates psychometric variables. So far we have achieved the combination of psychophysical measurements and multineuron recording in animals that receive sensory stimulation without movement (passive touch) (Stüttgen et al., 2006). We are on the way to establish frequency discrimination and directional discrimination as well. In the near future we intend to extend these measurement to active touch.

Haiss F, Schwarz C. (2005) Spatial segregation of different modes of movement control in the whisker representation of rat primary motor cortex. J. Neurosci. 25:1579-1587.

Hentschke, H., Haiss, F., Schwarz, C. (2006) Central signals rapidly switch tactile processing in rat barrel cortex during whisker movements. Cerebral Cortex 16:1142-1156.

Stüttgen, M.C., Rüter, J., and Schwarz, C. (2006) Evidence for two separate psychophysical channels as revealed by precise whisker deflections in operantly conditioned rats. J. Neurosci. 26:7933-7941.
The talk is open to the public. Guests are cordially invited!