Thalamocortical Inputs Show Post-Critical-Period Plasticity

• Published in: Neuron (Cambridge, Mass.) Vol. 74; no. 4; pp. 731 - 742
• Main Authors: Yu, Xin, Chung, Seungsoo, Chen, Der-Yow, Wang, Shumin, Dodd, Stephen J., Walters, Judith R., Isaac, John T.R., Koretsky, Alan P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 24.05.2012; Elsevier Limited
• Subjects: Animals; Brain injury; Brain research; Brain slice preparation; Circuits; Cortex; Cortex (barrel); Cortex (somatosensory); Critical period; Critical Period (Psychology); Electrophysiology; Excitatory Postsynaptic Potentials - physiology; Functional magnetic resonance imaging; Magnetic Resonance Imaging; Neural Pathways - physiology; Neuronal Plasticity - physiology; Peripheral nerves; Plasticity (functional); Plasticity (synaptic); Potentiation; Rats; Rats, Sprague-Dawley; Rehabilitation; Rodents; Somatosensory Cortex - physiology; stellate cells; Synapses - physiology; Synaptic strength; Thalamus; Thalamus - physiology
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2012.04.024

Experience-dependent plasticity in the adult brain has clinical potential for functional rehabilitation following central and peripheral nerve injuries. Here, plasticity induced by unilateral infraorbital (IO) nerve resection in 4-week-old rats was mapped using MRI and synaptic mechanisms were elucidated by slice electrophysiology. Functional MRI demonstrates a cortical potentiation compared to thalamus 2 weeks after IO nerve resection. Tracing thalamocortical (TC) projections with manganese-enhanced MRI revealed circuit changes in the spared layer 4 (L4) barrel cortex. Brain slice electrophysiology revealed TC input strengthening onto L4 stellate cells due to an increase in postsynaptic strength and the number of functional synapses. This work shows that the TC input is a site for robust plasticity after the end of the previously defined critical period for this input. Thus, TC inputs may represent a major site for adult plasticity in contrast to the consensus that adult plasticity mainly occurs at cortico-cortical connections. ► Thalamocortical input is a site for robust plasticity in the mature brain ► MRI pinpointed neuroplasticity at the laminar level in layer 4 barrel cortex ► Patch-clamp slice electrophysiology identified synaptic mechanisms Yu et al. use fMRI and slice electrophysiology to assess plasticity mechanisms in the barrel cortex mature rats. Results indicate that layer 4 thalamocortical plasticity occurs in the mature brain after the critical period.