Thalamic synchrony and the adaptive gating of information flow to cortex.

Although it has long been posited that sensory adaptation serves to enhance information flow in sensory pathways, the neural basis remains elusive. Simultaneous single-unit recordings in the thalamus and cortex in anesthetized rats showed that adaptation differentially influenced thalamus and cortex in a manner that fundamentally changed the nature of information conveyed about vibrissa motion. Using an ideal observer of cortical activity, we found that performance in detecting vibrissal deflections degraded with adaptation while performance in discriminating among vibrissal deflections of different velocities was enhanced, a trend not observed in thalamus. Analysis of simultaneously recorded thalamic neurons did reveal, however, an analogous adaptive change in thalamic synchrony that mirrored the cortical response. An integrate-and-fire model using experimentally measured thalamic input reproduced the observed transformations. The results here suggest a shift in coding strategy with adaptation that directly controls information relayed to cortex, which could have implications for encoding velocity signatures of textures.