Infragranular barrel cortex activity is enhanced with learning

Ward RL, Flores LC, Disterhoft JF. Infragranular barrel cortex activity is enhanced with learning. J Neurophysiol 108: 1278-1287, 2012. First published June 13, 2012; doi:10.1152/jn.00305.2012.-The barrel cortex (BC) is essential for the acquisition of whisker-signaled trace eyeblink conditioning and shows learning-related expansion of the trained barrels after the acquisition of a whisker-signaled task. Most previous research examining the role of the BC in learning has focused on anatomic changes in the layer IV representation of the cortical barrels. We studied single-unit extracellular recordings from individual neurons in layers V and VI of the BC as rabbits acquired the whisker-signaled trace eyeblink conditioning task. Neurons in layers V and VI in both conditioned and pseudoconditioned animals robustly responded to whisker stimulation, but neurons in conditioned animals showed a significant enhancement in responsiveness in concert with learning. Learning-related changes in firing rate occurred as early as the day of learning criterion within the infragranular layers of the primary sensory cortex.