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