Brain cells that respond to whisker stimulation in rats have been shown to be tuned to the direction that the whisker is moved. The 30 or so large whiskers on either side of a rat’s snout work together to explore the environment.
A study published in the January 20, 2010 issue of the Journal of Neuroscience titled “Feedforward Inhibition Determines the Angular Tuning of Vibrissal Responses in the Principal Trigeminal Nucleus” examines directional (angular) tuning responses of brain cells in the first processing station in the brain.
Two important results of the study were:
1) directional tuning is may be observed in these brain cells by counting the number of impulses evoked in each direction and observing the direction that evokes the most brain impulses or observing he direction that evokes impulses in the shortest time from when the whisker was moved
2) inhibition in this first whisker related processing station in the brain sharpens directional tuning.
The contribution of inhibition in sharpening directional selectivity of whisker (technically vibrissae) responses may prove important for retaining a relatively high degree of directional tuning in the brain. Modulation of inhibition could also enable the brain to dynamically influence the sharpness of directional tuning.
Showing that directional tuning may be measured by impulse timing is a major contribution of this paper.
Future posts to this blog will address the significance of these and other findings to the rat’s (and our own) ability to explore objects by touching them.
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