title: Target structures for cochlear infrared neural stimulation.
abstract: Infrared neural stimulation (INS) is a method to depolarize neurons with infrared light. While consensus exists that heating of the target structure is essential, subsequent steps that result in the generation of an action potential are controversially discussed in the literature. The question of whether cochlear INS is an acoustic event has not been clarified. Results have been published that could be explained solely by an acoustic event. However, data exist that do not support an acoustical stimulus as the dominant factor in cochlear INS. We review the different findings that have been suggested for the mechanism of INS. Furthermore, we present the data that clarify the role of an acoustical event in cochlear INS. Masking experiments have been performed in hearing, hearing impaired, and severely hearing impaired animals. In normal hearing animals, the laser response could be masked by the acoustic stimulus. Once thresholds to acoustic stimuli were elevated, the ability to acoustically mask the INS response gradually disappeared. Thresholds for acoustic stimuli were significantly elevated in animals with compromised cochlear function, while the thresholds for optical stimulation remained largely unchanged. The results suggest that the direct interaction between the radiation and the target structure dominates cochlear INS.
authors.affiliation: Northwestern University , Department of Otolaryngology, 303 East Chicago Avenue, Searle 12-561, Chicago, Illinois 60611, United States.
authors.forename: Hunter K
authors.initials: HK
authors.lastname: Young
authors.affiliation: Northwestern University , Department of Otolaryngology, 303 East Chicago Avenue, Searle 12-561, Chicago, Illinois 60611, United States.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Tan
authors.affiliation: Northwestern University , Department of Otolaryngology, 303 East Chicago Avenue, Searle 12-561, Chicago, Illinois 60611, United States ; Chongqing University , Key Laboratory of Biorheological Science and Technology, Ministry of Education, 174 Shazheng Street, Chongqing 400044, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Xia
authors.affiliation: Northwestern University , Department of Otolaryngology, 303 East Chicago Avenue, Searle 12-561, Chicago, Illinois 60611, United States ; Northwestern University , Department of Biomedical Engineering, 2145 Sheridan Road, Tech E310, Evanston, Illinois 60208, United States ; Northwestern University , The Hugh Knowles Center, Department of Communication Sciences and Disorders, 2240 Campus Drive, Evanston, Illinois 60208, United States.
authors.forename: Claus-Peter
authors.initials: CP
authors.lastname: Richter
keywords: guinea pig; hearing; infrared neural stimulation; laser; masking; optoacoustics