Transient Adaptation Properties in Rat Barrel Cortex are Affected by the Initial Direction of Vibrissa Deflection

Roxanna M. Webber and Garrett B. Stanley
Division of Engineering and Applied Sciences
Harvard University

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Rats can discriminate between similar periodic textures using only their vibrissae. However, neurons in the barrel cortex, as in other sensory systems, exhibit pronounced adaptation to periodic stimulation. This suggests that properties of the transient adaptation response, before the neuron reaches steady state, could be important in texture encoding. In anesthetized Sprague-Dawley rats, adaptation of cortical cells occurs at frequencies above 4 Hz and reaches a steady state response level after several stimulus cycles. We previously developed a prediction method that captured the steady state properties of barrel neurons. Although the steady state behavior of the neurons is well documented, little attention has been paid to the transient portion of the adaptation. To address this issue, we deflected primary vibrissae in alternating directions at frequencies between 1 and 16 Hz. Two main adaptation properties were seen with this stimulation; neurons either adapted to the same steady state value for both directions, or they adapted more to one direction than the other. These properties are dependent on the size of the excitation and suppression induced by each direction of deflection. When the same stimulus was presented to the vibrissa in the opposite direction, the neuronal response converged to the same steady state value but the transient dynamics of adaptation were altered. These dynamics are captured through our prediction method. This suggests that the initial conditions, in this case the direction of vibrissa deflection, play a role in the transient adaptation properties of barrel cortex neurons and could be involved in texture encoding.

This work was supported by an NSF graduate research fellowship to R. M. Webber, the Whitaker Foundation, and the Whitehall Foundation.