(a) Early Hearing-Impaired
(b) Hearing
Figure 9: Sources of thalamic inputs to core auditory cortices for early hearing-impaired (a) and normal hearing (b) ferrets. On serially arranged (anterior:left) coronal sections through the thalamus of an early hearing-impaired ferret, tracer injection (BDA; solid grey area) into core auditory cortex produced retrogradely labeled neurons (1 dot = 1 neuron) essentially within the regions regarded as auditory thalamus: in the medial geniculate nucleus (MG). No retrgradely labeled neurons were identified in somatosensory (Vb) or visual (LGN) thalamus although a few were found in the border of the lateral posterior (LP) and posterior (Po) nuclei. Although a larger injection in a hearing animal encroached on the secondary auditory fields, the thalamic labeling was focused on the MG, with lesser connectivity with the LP and Po; no labeled neurons were observed in somatosensory (Vb) or visual (LGN) thalamic nuclei. Hearing controls replotted from [13].