PLASTICITY OF METABOLIC WHISKER MAPS IN SOMATOSENSORY BRAIN-STEM AND THALAMUS OF MICE WITH NEONATAL LESIONS OF WHISKER FOLLICLES

We employed the autoradiographic deoxyglucose method to study metaboli c whisker maps of the adult mouse somatosensory brainstem and thalamus after the neonatal removal of left whisker follicles C1, C2 and C3. L eft whiskers B1-3 and D1-3 were deflected to metabolically activate th e somatosensory pathway. Unoperated mice that were stimulated in the s ame fashion served as controls, Whisker stimulation resulted in an ips ilateral increase in metabolic activity in the three trigeminal brains tem structures in which the whiskers are represented topologically by segments of high cytochrome oxidase activity, i.e. subnucleus caudalis , subnucleus interpolaris and nucleus principalis. In the two subnucle i of mice with lesions and of controls, there was an increase in metab olic activity of the representations of the deflected whiskers, wherea s the metabolic activity of representations A1-3 and E1-3 was low. Apa rt from these similarities, the metabolic activation of the representa tions originally representing whiskers C1-3 was remarkably greater in mice with lesions than in controls. This increase reached statistical significance in subnucleus caudalis and approached statistical signifi cance in subnucleus interpolaris. In nucleus principalis the deprived territory was only partially activated and the degree of metabolic act ivation was less than in the subnuclei. In the thalamic ventrobasal co mplex of mice with lesions metabolic activity was unpatterned whereas two areas of metabolic activation were distinct in controls. Hence, th e removal of whisker follicles in newborn mice resulted in the suppres sion of localized metabolic responses to whisker stimulation in the th alamus, whereas in the brainstem stimulus-related activity was promine nt and the deprived territory became responsive to the stimulation of whisker follicles adjacent to the lesion. Apparently, the modification of the whisker representation at the first synapse of the pathway ind uces a diminution of localized responsivity in the thalamus.