Central Systems Laboratory
John Middlebrooks, Ph.D., Laboratory Director
Research in the Central Systems Lab examines the brain mechanisms of hearing, particularly issues related to stimulus coding in the auditory cortex. Current projects involve spatial hearing and auditory prosthesis. We study spatial hearing because awareness of the locations of sound-sources in space is a prominent feature of the human sensory experience, because sound localization is performed well by most laboratory animals, and because sound localization requires a significant degree of central integration. Experimental approaches include psychophysical studies with normal human listeners, cortical physiology studies with behaving animals, and computational modeling. We recently have begun studies of cortical substrates of auditory scene analysis, specifically spatial release from informational masking and spatial stream segregation.
Our work on auditory prosthesis involves animal studies of conventional cochlear implants and of a new mode of auditory prosthesis involving a penetrating intra-neural electrode array. In the cochlear-implant studies, our goal is to improve the transfer of information from a cochlear prosthesis to the auditory cortex and, thereby, to improve human speech reception. Those experiments utilize an animal model in which we stimulate a cochlear prosthesis and record from ensembles of neurons in the auditory cortex and in the inferior colliculus. The intra-neural stimulation studies involve placement of a stimulating electrode array directly into the auditory nerve, with recording in the inferior colliculus. We are finding that direct intra-neural stimulation enables more precise stimulation of specific auditory nerve populations, permitting more effective transmission of spectral information and a larger number of channels of information from the prosthesis to the brain. Steps to translate the animal results to human trials of intra-neural stimulation are under way.
