Feasibility evaluation of transtympanic laser stimulation of the cochlea from the outer ear

Infrared laser stimulation has been studied as an alternative approach to auditory prostheses. This study evaluated the feasibility of infrared laser stimulation of the cochlea from the outer ear bypassing the middle ear function. An optic fiber was inserted into the ear canal and a laser was used to irradiate the cochlea through the tympanic membrane in Mongolian gerbil. A pulsed infrared laser (10.1 mJ/cm2) and clicking sound (70 peak-to-peak equivalent sound pressure level) were presented to the animals. The amplitude of the laser-evoked cochlear response was systematically decreased following insertion of a filter between the tympanic membrane and cochlea; however, the auditory-evoked cochlear response did not decrease. The filter was removed and the laser-evoked response returned to around the original level. The amplitude ratio and the relative change in response amplitude before and during filter insertion significantly decreased as the absorbance of the infrared filter increased. These results indicate that laser irradiation could bypass the function of the middle ear and directly activate the cochlea. Therefore, an auditory prosthesis based on laser stimulation represents a possible noninvasive alternative to conventional auditory prostheses requiring surgical implants.

Speech intelligibility predicted from neural entrainment of the speech envelope

Speech intelligibility is currently measured by scoring how well a person can identify a speech signal. The results of such behavioral measures reflect neural processing of the speech signal, but are also influenced by language processing, motivation and memory. Very often electrophysiological measures of hearing give insight in the neural processing of sound. However, in most methods non-speech stimuli are used, making it hard to relate the results to behavioral measures of speech intelligibility. The use of natural running speech as a stimulus in electrophysiological measures of hearing is a paradigm shift which allows to bridge the gap between behavioral and electrophysiological measures. Here, by decoding the speech envelope from the electroencephalogram, and correlating it with the stimulus envelope, we demonstrate an electrophysiological measure of neural processing of running speech. We show that behaviorally measured speech intelligibility is strongly correlated with our electrophysiological measure. Our results pave the way towards an objective and automatic way of assessing neural processing of speech presented through auditory prostheses, reducing confounds such as attention and cognitive capabilities. We anticipate that our electrophysiological measure will allow better differential diagnosis of the auditory system, and will allow the development of closed-loop auditory prostheses that automatically adapt to individual users.

Effect of sound amplification in speech perception in elderly with and without tinnitus

PURPOSE: To verify the effect of the use of auditory prostheses on speech perception tests in elderly individuals with and without tinnitus having hearing impairment.METHODS: We evaluated 24 elderly patients with moderate sensorineural hearing loss, aged between 60 and 70 years, distributed into two groups according to the presence or absence of tinnitus. All of them were fitted with micro-canal auditory prostheses from the same manufacturer and model, and underwent speech perception tests. The assessments were performed with and without the amplification devices after 1 and 3 months of effective use. For data analysis, Mann-Whitney test was used.RESULTS: Elderly people from the tinnitus group presented lower performance in speech perception tests than those from the group without tinnitus. In the evaluations with the devices, the performance of both groups was better than when they were evaluated without hearing aids.CONCLUSION: The acoustic stimulation through the effective use of hearing aids produced better speech perception, regardless of the presence of tinnitus.