title: A method to dynamically control unwanted loudness cues when measuring amplitude modulation detection in cochlear implant users.
abstract: BACKGROUND
  Amplitude modulation (AM) detection is a measure of temporal processing that has been correlated with cochlear implant (CI) users' speech understanding. For CI users, AM stimuli have been shown to be louder than steady-state (non-AM) stimuli presented at the same reference current level, suggesting that unwanted loudness cues might contribute to CI users' AM sensitivity as measured in a modulation detection task. In this paper, a new method is introduced to dynamically control unwanted AM loudness cues when adaptively measuring modulation detection thresholds (MDTs) in CI users.
  
  
  METHODS
  MDTs were adaptively measured in 9 CI subjects using a three-alternative, forced-choice procedure, with and without dynamic control of unwanted AM loudness cues. To control for AM loudness cues during the MDT task, the level of the steady-state (non-AM) stimuli was increased to match the loudness of the AM stimulus using a non-linear amplitude scaling function, which was obtained by first loudness-balancing non-AM stimuli to AM stimuli at various modulation depths. To further protect against unwanted loudness cues, ±0.75dB of level roving was also applied to all stimuli during the MDT task.
  
  
  RESULTS
  Absolute MDTs were generally poorer when unwanted AM loudness cues were controlled. However, the effects of modulation frequency and presentation level on modulation sensitivity were fundamentally unchanged by the availability of AM loudness cues.
  
  
  CONCLUSIONS
  The data suggest that the present method controlling for unwanted AM loudness cues might better represent CI users' MDTs, without changing fundamental effects of modulation frequency and presentation level on CI users' modulation sensitivity.
authors.affiliation: Division of Communication and Auditory Neuroscience, House Research Institute, Los Angeles, CA, USA; University of California Los Angeles, David Geffen School of Medicine Department of Head and Neck Surgery, Los Angeles, CA, USA; Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen, Groningen, The Netherlands. Electronic address: JGalvin@mednet.ucla.edu.
authors.forename: John J
authors.initials: JJ
authors.lastname: Galvin
authors.affiliation: Division of Communication and Auditory Neuroscience, House Research Institute, Los Angeles, CA, USA; University of California Los Angeles, David Geffen School of Medicine Department of Head and Neck Surgery, Los Angeles, CA, USA.
authors.forename: Qian-Jie
authors.initials: QJ
authors.lastname: Fu
authors.affiliation: Division of Communication and Auditory Neuroscience, House Research Institute, Los Angeles, CA, USA; University of California Los Angeles, David Geffen School of Medicine Department of Head and Neck Surgery, Los Angeles, CA, USA.
authors.forename: Sandy
authors.initials: S
authors.lastname: Oba
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen, Groningen, The Netherlands.
authors.forename: Deniz
authors.initials: D
authors.lastname: Başkent
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001307:Auditory Perception; D003054:Cochlear Implants; D003463:Cues; D003638:Deafness / Q000628:therapy; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017711:Nonlinear Dynamics; D011571:Psychoacoustics; D013998:Time Perception
keywords: AM; Amplitude modulation; CI; Cochlear implant; DR; LL; Loudness; MAL; MDT; Modulation detection; PPS; RM ANOVA; Stimulation rate; amplitude modulated; cochlear implant; dynamic range; loudness-balanced level; maximum acceptable loudness; modulation detection threshold; pulses per second; repeated measures analysis of variance