Audiovisual integra0on in the implanted auditory cortex measured by near-‐infrared spectroscopy
L.P.H. van de Rijt, E.A.M. Mylanus, A.F.M. Snik, M.M. van Wanrooij 17 October 2014
Research problem • Early hearing loss disrupts normal development of the auditory system.
• How does restoraKon of peripheral hearing by implanKng a cochlear implant (CI) affect central auditory processing?
Objec0ves • To determine the feasibility of recording brain acKvity of postlingually deaf
individuals aSer cochlear implantaKon with near-‐infrared spectroscopy.
• To compare the cross-‐sensory acKvaKon of auditory cortex of implanted and normal-‐hearing individuals with near-‐infrared spectroscopy
Methods • Par0cipants. • 21 normal-‐hearing adults (male vs. female) and (age range) • 5 postlingually deaf CI-‐users
• Task. • View and listen to segments of a story (‘passive listening’).
Methods • Recordings • Schema0c layout of optodes
2 lasers = 1 source
Background • Near-‐infrared spectroscopy • Biological Kssue is relaKvely transparent to light in the near infrared
region (700-‐1300 nm). • It is possible to transmit enough photons through organs for in situ
monitoring. • Hemodynamic response
Results -‐ Raw • Example trace
Results – average normal-‐hearing • Hemodynamic responses of all normal-‐hearing subjects
Results – average CI user • Group-‐averaged hemodynamic responses of all CI users
Stein, B. E., Stanford, T. R., Ramachandran, R., Perrault, T. J., & Rowland, B. A. (2009). Exp Brain Res, 198(2-‐3)
Integra0on effect
Results – normal hearing Auditory response amplitude > visual The audiovisual response amplitude demonstrates a sub-‐addi0ve effect for deoxyhemoglobin only. For oxyhemoglobin, the audiovisual does not differ significantly from the auditory response.
Results – CI Auditory response amplitude > visual The audiovisual response amplitude hints at a sub-‐addi0ve effect for oxyhemoglobin only. For deoxyhemoglobin, the audiovisual does not differ significantly from the auditory response.
Conclusion • Auditory corKcal responses are evoked for all sKmulus modaliKes in both
hemispheres; • Largest unisensory changes for auditory s0muli. • smallest concentraKon changes for the unisensory visual s0mula0on. • IntegraKon effects are small or negligible: preliminary results hint at
subaddiKve effects both for normal-‐hearing and for CI users
Overall, normal-‐hearing parKcipants and postlingually deaf CI users tend to demonstrate similar responses.
Acknowledgements − L.P.H. van de Rijt1,2 − A.F.M. Snik2 − L.V. Straatman2
− H.Y. Hu1 − A.J. van Opstal1 − M.M. van Wanrooij1,2
1. Radboud University, Donders InsKtute for Brain, CogniKon and Behavior, Department of Biophysics, Nijmegen, the Netherlands
2. Radboudumc, Department of Otorhinolaryngology, Nijmegen, the Netherlands Supported by Cochlear
Top Related