Early thalamocortical connections: Just how different are they?
Thalamocortical circuits undergo a dramatic shift in preparation for the sudden onset of rich sensory experience at birth. In a matter of weeks, fetal thalamic sensory circuits tuned for transmission of spontaneous bursting switch to circuits capable of high resolution, active sensory processing. This 'Pre-Sensory' stage of thalamocortical function uses 'booster circuits' to amplify nascent incoming activity and ensure transmission of bursts, at the expense of stimulus discrimination. The switch to 'Sensory' circuits that allows higher quality sensation at birth is due, at least in part, to the coordinated remodeling of inhibitory circuits in thalamus and cortex. Early circuits thus follow rules quite distinct from postnatal ones for the very different goals of pathfinding and topography vs high quality sensation.