title: Spectral loudness summation for electrical stimulation in cochlear implant users.
abstract: OBJECTIVE
  This study investigates the effect of spectral loudness summation (SLS) in the electrical domain as perceived by cochlear implant (CI) users. Analogous to SLS in the acoustical domain, SLS was defined as the effect of electrode separation at a fixed overall stimulation rate.
  
  
  METHODS
  Categorical loudness scaling (CLS) was conducted at three overall stimulation rates using single-electrode stimuli and multi-electrode stimuli presented interleaved on two or four electrodes. The specific loudness of the pulses in the multi-electrode stimuli were equalized based on single-electrode measurements at the same overall stimulation rate. At a fixed overall stimulation rate and a fixed loudness perception, SLS was calculated as the difference in mean current between single-electrode and multi-electrode stimuli.
  
  
  METHODS
  Ten postlingually deafened adult CI users.
  
  
  RESULTS
  The amount of SLS varied between subjects and between the number and location of the stimulated electrodes in the multi-electrode configuration. SLS was significantly higher than 0 for a subset of the subjects.
  
  
  CONCLUSIONS
  For a subpopulation of CI users, loudness models should account for nonlinear interactions between electrodes (in the perceptual domain). Similarly, SLS should be accounted for when using CLS outcomes for fitting purposes, at least in a subpopulation of CI users.
authors.affiliation: a Academic Medical Center Amsterdam, Clinical and Experimental Audiology , The Netherlands.
authors.forename: Femke L
authors.initials: FL
authors.lastname: Theelen-van den Hoek
authors.affiliation: a Academic Medical Center Amsterdam, Clinical and Experimental Audiology , The Netherlands.
authors.forename: Monique
authors.initials: M
authors.lastname: Boymans
authors.affiliation: a Academic Medical Center Amsterdam, Clinical and Experimental Audiology , The Netherlands.
authors.forename: Wouter A
authors.initials: WA
authors.lastname: Dreschler
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003054:Cochlear Implants; D005260:Female; D006801:Humans; D008144:Loudness Perception; D008297:Male; D008875:Middle Aged
keywords: Cochlear implant; categorical loudness scaling; loudness growth; loudness perception; spectral loudness summation