Laser-induced auditory perception: transtympanic laser irradiation of the cochlea from the outer ear evokes an auditory-related neural and behavioral response

Brain-machine interfaces are emerging devices that act as a medium for communication between the neural system and external software and hardware. Over the last decade, there has been a discussion on applying infrared laser stimulation to the brain-machine interfaces, including cochlear implants. Infrared lasers can selectively activate neural populations without introducing exogenous agents to tissues. This study presents the first demonstration that laser irradiation of the cochlea, a peripheral sensory organ, can elicit a clear behavioral auditory response. Mongolian gerbils (Meriones unguiculatus) were divided into two groups, each subjected to classical conditioning where a reward water delivery was predicted by either cochlear laser stimulation or sound stimulus. Laser-conditioned animals successfully learned licking behavior, with conditioned responses and behavioral properties comparable to auditory-conditioned animals. The laser-evoked response was significantly inhibited by auditory masking, and auditory-conditioned animals demonstrated stimulus generalization to laser stimulation. In a subsequent experiment, simultaneous presentation of auditory and laser stimulation induced nonlinear amplification in both auditory cortical and behavioral responses, suggesting that combining auditory and laser stimulation can enhance auditory perception beyond the effects of each stimulus alone. These findings indicate that infrared laser irradiation of the cochlea can potentially evoke and enhance auditory perception, making it a promising candidate for implementation in auditory prostheses.