Pre-neuronal morphological processing of object location by individual whiskers

Area of Science:

• Neuroscience
• Biophysics
• Sensory systems

Background:

• The vibrissal system in mammals uses mechanoreceptors in whisker follicles to transmit touch information to the brain.
• The potential for information processing within the whisker itself, prior to neural transmission, remains largely unexplored.

Purpose of the Study:

• To investigate whether the whisker hair undergoes processing of touch information before it reaches the mechanoreceptors.
• To determine if the physical properties of the whisker contribute to sensory coding.

Main Methods:

• High-speed videography was employed to track whisker movements in both anesthetized and behaving rats during tactile exploration.
• Analysis focused on morphological variables such as angle and curvature to define phase planes.
• Exposed whisker follicles were tracked to assess the rigidity of the follicle-whisker junction.

Main Results:

• Whisker morphology, specifically angular and curvature variables, reliably encodes object position coordinates post-contact, aligning with theoretical models.
• The junction between the whisker and its follicle was found to be rigid, allowing direct mechanoreceptor readout of whisker shape.
• Behaving rats actively manipulated their whiskers against objects, inducing significant morphological coding and improving localization accuracy.

Conclusions:

• The whisker hair itself acts as a site for pre-neuronal computation, transforming tactile input through its morphology.
• The rigidity of the follicle-whisker junction facilitates direct interpretation of this morphological code by mechanoreceptors.
• Active vibrissal touch involves pre-neuronal morphological computation, playing a crucial role in enhancing spatial localization.