Strengthening of Thalamocortical Synapses at Layer IV in the Juvenile Whisker Barrel Measured by MRI & Electrophysiology

Xin Yu¹, Seungsoo Chung¹, Shumin Wang¹, Stephen Dodd¹, Judith Walters¹, John Isaac¹, Alan Koretsky¹

In juvenile rats, unilateral infraorbital denervation induces plasticity changes in the whisker-barrel system. Here, we focused on thalamocortical plasticity contralateral to the good whisker pad. Comparison of BOLD-fMRI of cortex and thalamus demonstrated a cortical specific signal increase. Manganese-enhanced MRI was applied to trace thalamocortical connections and estimated an increase of synaptic strength by measuring the transported Mn from thalamus into cortical Layer IV-V. In vitro slice electrophysiological recordings were applied to confirm this synaptic strengthening of the thalamocortical input. Therefore, MRI and electrophysiology indicate that plasticity to strengthen the barrel thalmocortical input occurs in the juvenile rodent.