Tactile Object Localization by Anticipatory Whisker Motion

Our paper on active sensorimotor processing in mice that I worked on with Tansu Celikel is out now. Thanks also to Dave Herman for running a bunch of very challenging moving gap crossing experiments!

Voigts J, Herman DH, Celikel T. Tactile Object Localization by Anticipatory Whisker Motion. 2014, Journal of neurophysiology 22:jn.00241.2014. doi: 10.1152/jn.00241.2014. (link)

When exploring a target that is suddenly retracted, whisker protractions initially stay the same, and the mouse temporarily 'underestimates' the distance.

When exploring a target that is suddenly retracted, whisker protraction amplitudes initially stay the same, and the mouse temporarily ‘underestimates’ the target distance.

In a nutshell: The way mice use whiskers to perceive their environment is a great model system for cortical sensory processing, and is especially interesting because whiskers are active sensory organs that are swept through space, requiring the integration of the motor signal of where the whiskers are and the sensory signal of when (and how) they touch objects.

Mice (and rats) don’t slam their whiskers into objects with force, but modulate their whisker protractions in order to only lightly touch the environment. In this study, we found that mice don’t simply stop their whiskers after they touch an object, but instead protract them to where they expect to find an object.

This may seem like a detail, but has interesting implications for the decoding of sensory information: If whiskers are protracted to expected object positions, then the timing (and force etc.) of contacts with the actual object  doesn’t simply encode the distance to that object, but instead encodes the prediction error. If somatosensory cortex expects to see such a ‘physically pre-computed’ error signal, this probably has implications to how we need to look at all cortical computation in this system. Further, we might be able to use this system as a convenient model for top-down/bottom-up integration.

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