Proprioceptive information from the pinna provides somatosensory input to cat dorsal cochlear nucleus

Abstract

The dorsal cochlear nucleus (DCN) is a second-order auditory structure that also receives nonauditory information, including somatosensory inputs from the dorsal column and spinal tri-geminal nuclei. Here we investigate the peripheral sources of the somatosensory inputs to DCN. Electrical stimulation was applied to cervical nerves C1–C8, branches of C2, branches of the trigeminal nerve, and hindlimb nerves. The largest evoked potentials in the DCN were produced by C2 stimulation and by stimulation of its branches that innervate the pinna. Electrical stimulation of C2 produced a pattern of inhibition and excitation of DCN principal cells comparable with that seen in previous studies with stimulation of the primary somatosensory nuclei, suggesting that the same pathway was activated. Because C2 contains both proprioceptive and cutaneous fibers, we applied peripheral somatosensory stimulation to identify the effective somatosensory modalities. Only stimuli that activate pinna muscle receptors, such as stretch or vibration of the muscles connected to the pinna, were effective in driving DCN units, whereas cutaneous stimuli such as light touch, brushing of hairs, and stretching of skin were ineffective. These results suggest that the largest somatosensory inputs to the DCN originate from muscle receptors associated with the pinna. They support the hypothesis that a role of the DCN in hearing is to coordinate pinna orientation to sounds or to support correc-tion for the effects of pinna orientation on sound-localization cues. Key words: auditory; somatosensory; dorsal cochlear nu-cleus; cat; pinna; multisensory; sound localization The output neurons of the dorsal cochlear nucleus (DCN) are sensitive to both auditory and somatosensory stimuli (Saade ́ et al., 1989; Young et al., 1995), suggesting a cross-modal associative role for the DCN. The somatosensory inputs to the DCN origi-nate predominantly from the ipsilateral dorsal column and spinal trigeminal nuclei (abbreviated MSN for medullary somatosensor