It has been reported1 that after complete decortication in the dog auditory acuity is appreciably impaired but acoustic function is by no means obliterated. Furthermore, such an animal can be differentially conditioned to pure tone (1,000 cycles) and complex sound (electric bell). The inference is that acoustic integration of a fairly high degree may occur in the absence of the cerebral cortex, that is, may be mediated by entirely subcortical mechanisms.
It has apparently been assumed that the residual acoustic function in the decorticate dog is mediated at the thalamic level, which can only mean the medial geniculate body through its efferent connections. The implication is that the medial geniculate body is not only a relay center in the central auditory pathway but an important reflex center as well. It is difficult to reconcile this conception with the fact that the medial geniculate body (pars dorsalis) very largely degenerates