The Journal of Neuroscience, May 15, 2001, 21(10):3549-3563
Tactile Responses in the Granule Cell Layer of Cerebellar Folium
Crus IIa of Freely Behaving Rats
Mitra J.
Hartmann and
James M.
Bower
California Institute of Technology, Biology Department, Pasadena,
CA 91125
We recorded activity from the granule cell layer (GCL) of
cerebellar folium Crus IIa as freely moving rats engaged in a variety of natural behaviors, including grooming, eating, and free tactile exploration. Multiunit responses in the 1000-4500 Hz range were found
to be strongly correlated with tactile stimulation of lip and whisker
(perioral) regions. These responses occurred regardless of whether the
stimulus was externally or self-generated and during both active and
passive touch. In contrast, perioral movements that did not tactually
stimulate this region of the face (e.g., chewing) produced no
detectable increases in GCL activity. In addition, GCL responses were
not correlated with movement extremes. When rats used their lips
actively for palpation and exploration, the tactile responses in the
GCL were not detectably modulated by ongoing jaw movements. However,
active palpation and exploratory behaviors did result in the largest
and most continuous bursts of GCL activity: responses were on average
10% larger and 50% longer during palpation and exploration than
during grooming or passive stimulation. Although activity levels
differed between behaviors, the position and spatial extent of the
peripheral receptive field was similar over all behaviors that resulted
in tactile input. Overall, our data suggest that the 1000-4500 Hz
multiunit responses in the Crus IIa GCL of awake rats are correlated
with tactile input rather than with movement or any movement parameter and that these responses are likely to be of particular importance during the acquisition of sensory information by perioral structures.
Key words:
cerebellar granule cells; mossy fibers; somatosensory; ingestive; grooming; exploration; whiskers; vibrissae; passive touch; active touch; active sensing
Copyright © 2001 Society for Neuroscience 0270-6474/01/21103549-15$05.00/0