Inferior Colliculus Responses to Multichannel Microstimulation of the Ventral Cochlear Nucleus: Implications for Auditory Brain Stem Implants

• Published in: Journal of neurophysiology Vol. 99; no. 1; pp. 1 - 13
• Main Authors: Shivdasani, Mohit N, Mauger, Stefan J, Rathbone, Graeme D, Paolini, Antonio G
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01.01.2008
• Subjects: Action Potentials - physiology; Animals; Auditory Brain Stem Implants - standards; Auditory Diseases, Central - therapy; Auditory Pathways - anatomy & histology; Auditory Pathways - physiology; Auditory Perception - physiology; Auditory Threshold - physiology; Brain Mapping; Cochlear Nucleus - anatomy & histology; Cochlear Nucleus - physiology; Electric Stimulation - methods; Electrodes, Implanted - standards; Inferior Colliculi - anatomy & histology; Inferior Colliculi - physiology; Male; Neurons - physiology; Pitch Perception - physiology; Rats; Rats, Wistar
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00629.2007

1 The Bionic Ear Institute, East Melbourne Victoria; and 2 School of Psychological Science and 3 Department of Electronic Engineering, La Trobe University, Melbourne, Victoria, Australia Submitted 7 June 2007; accepted in final form 6 October 2007 Multichannel techniques were used to assess the frequency specificity of activation in the central nucleus of the inferior colliculus (CIC) produced by electrical stimulation of localized regions within the ventral cochlear nucleus (VCN). Data were recorded in response to pure tones from 141 and 193 multiunit clusters in the rat VCN and the CIC, respectively. Of 141 VCN sites, 126 were individually stimulated while recording responses in the CIC. A variety of CIC response types were seen with an increase in both electrical and acoustic stimulation levels. The majority of sites exhibited monotonic rate-level types acoustically, whereas spike rate saturation was achieved predominantly with electrical stimulation. In 20.6% of the 364 characteristic frequency aligned VCN–CIC pairs, the CIC sites did not respond to stimulation. In 26% of the 193 CIC sites, a high correlation was observed between acoustic tuning and electrical tuning obtained through VCN stimulation. A high degree of frequency specificity was found in 58% of the 118 lowest threshold VCN–CIC pairs. This was dependent on electrode placement within the VCN because a higher degree of frequency specificity was achieved with stimulation of medial, central, and posterolateral VCN regions than more anterolateral regions. Broadness of acoustic tuning in the CIC played a role in frequency-specific activation. Narrowly tuned CIC sites showed the lowest degree of frequency specificity on stimulation of the anterolateral VCN regions. These data provide significant implications for auditory brain stem implant electrode placement, current localization, power requirements, and facilitation of information transfer to higher brain centers. Address for reprint requests and other correspondence: A. G. Paolini, Auditory Clinical Neuroscience Unit, The Bionic Ear Institute, 6th Floor Daly Wing, St. Vincent's Hospital, Victoria Parade, Fitzroy, VIC 3065, Australia (E-mail: tpaolini{at}bionicear.org )