Central signals rapidly switch tactile processing in rat barrel cortex during whisker movements

Area of Science:

• Neuroscience
• Somatosensation
• Tactile Sensing

Background:

• Palpatory movements, or active touch, are crucial for tactile sensing.
• The modulation of tactile signals during active touch is known, but its source (kinematic or central) remains unclear.

Purpose of the Study:

• To investigate the contribution of movement kinematics versus central motor signals to tactile processing during active touch.
• To determine the neural mechanisms underlying the rapid modulation of tactile responses during active touch.

Main Methods:

• Used awake, head-fixed rats trained to contact objects with their whiskers.
• Precisely measured whisker movement kinematics and recorded neural activity in the barrel cortex.
• Compared neural responses to active (self-propelled) and passive (externally moved) touch, and tested responses after infraorbital nerve transection.

Main Results:

• Active touch resulted in a switch to low response amplitudes, narrow spatial representation, and elevated background firing in the barrel cortex, compared to passive touch.
• This switch occurred rapidly (<100 ms) and was independent of alertness levels.
• The observed changes persisted even when whisker kinematic information was removed, suggesting a central origin.

Conclusions:

• Central signals from the motor system significantly contribute to the processing of active touch.
• The brain rapidly modulates tactile processing based on motor commands, not solely on peripheral sensory input.
• This study provides evidence for the role of efference copy or corollary discharge in tactile perception.