TY - JOUR
T1 - Effect of stimulus polarity on physiological spread of excitation in cochlear implants
AU - Spitzer, Emily R.
AU - Hughes, Michelle L.
N1 - Funding Information:
*Boys Town National Research Hospital, Omaha, NE; †University of North Carolina-Chapel Hill, Chapel Hill, NC Corresponding author: Michelle L. Hughes, Boys Town National Research Hospital, Omaha, NE 68131; E-mail: [email protected] This research was supported by grants R01 DC009595, P30 DC04662, and T35 DC008757 from the NIH and NIDCD. Data from this study was presented at the 2017 American Auditory Society Scientific and Technology Meeting, Scottsdale, AZ, March 2–4, 2017. The content of this project is solely the responsibility of the authors and does not necessarily represent the official views of the NIDCD or the NIH.
PY - 2017/10
Y1 - 2017/10
N2 - Background: Contemporary cochlear implants (CIs) use cathodic-leading, symmetrical, biphasic current pulses, despite a growing body of evidence that suggests anodic-leading pulses may be more effective at stimulating the auditory system. However, since much of this research on humans has used pseudomonophasic pulses or biphasic pulses with unusually long interphase gaps, the effects of stimulus polarity are unclear for clinically relevant (i.e., symmetric biphasic) stimuli. Purpose: The purpose of this study was to examine the effects of stimulus polarity on basic characteristics of physiological spread-of-excitation (SOE) measures obtained with the electrically evoked compound action potential (ECAP) in CI recipients using clinically relevant stimuli. Research Design: Using a within-subjects (repeated measures) design, we examined the differences in mean amplitude, peak electrode location, area under the curve, and spatial separation between SOE curves obtained with anodic- and cathodic-leading symmetrical, biphasic pulses. Study Sample: Fifteen CI recipients (ages 13-77) participated in this study. All were users of Cochlear Ltd. devices. Data Collection and Analysis: SOE functions were obtained using the standard forward-masking artifact reduction method. Probe electrodes were 5-18, and they were stimulated at an 8 (of 10) loudness rating ("loud"). Outcome measures (mean amplitude, peak electrode location, curve area, and spatial separation) for each polarity were compared within subjects. Results: Anodic-leading current pulses produced ECAPs with larger average amplitudes, greater curve area, and less spatial separation between SOE patterns compared with that for cathodic-leading pulses. There was no effect of polarity on peak electrode location. Conclusions: These results indicate that for equal current levels, the anodic-leading polarity produces broader excitation patterns compared with cathodic-leading pulses, which reduces the spatial separation between functions. This result is likely due to preferential stimulation of the central axon. Further research is needed to determine whether SOE patterns obtained with anodic-leading pulses better predict pitch discrimination.
AB - Background: Contemporary cochlear implants (CIs) use cathodic-leading, symmetrical, biphasic current pulses, despite a growing body of evidence that suggests anodic-leading pulses may be more effective at stimulating the auditory system. However, since much of this research on humans has used pseudomonophasic pulses or biphasic pulses with unusually long interphase gaps, the effects of stimulus polarity are unclear for clinically relevant (i.e., symmetric biphasic) stimuli. Purpose: The purpose of this study was to examine the effects of stimulus polarity on basic characteristics of physiological spread-of-excitation (SOE) measures obtained with the electrically evoked compound action potential (ECAP) in CI recipients using clinically relevant stimuli. Research Design: Using a within-subjects (repeated measures) design, we examined the differences in mean amplitude, peak electrode location, area under the curve, and spatial separation between SOE curves obtained with anodic- and cathodic-leading symmetrical, biphasic pulses. Study Sample: Fifteen CI recipients (ages 13-77) participated in this study. All were users of Cochlear Ltd. devices. Data Collection and Analysis: SOE functions were obtained using the standard forward-masking artifact reduction method. Probe electrodes were 5-18, and they were stimulated at an 8 (of 10) loudness rating ("loud"). Outcome measures (mean amplitude, peak electrode location, curve area, and spatial separation) for each polarity were compared within subjects. Results: Anodic-leading current pulses produced ECAPs with larger average amplitudes, greater curve area, and less spatial separation between SOE patterns compared with that for cathodic-leading pulses. There was no effect of polarity on peak electrode location. Conclusions: These results indicate that for equal current levels, the anodic-leading polarity produces broader excitation patterns compared with cathodic-leading pulses, which reduces the spatial separation between functions. This result is likely due to preferential stimulation of the central axon. Further research is needed to determine whether SOE patterns obtained with anodic-leading pulses better predict pitch discrimination.
KW - Cochlear implant
KW - Electrically evoked compound action potential
KW - Spread of excitation
KW - Stimulus polarity
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U2 - 10.3766/jaaa.16144
DO - 10.3766/jaaa.16144
M3 - Article
C2 - 28972468
AN - SCOPUS:85030327451
SN - 1050-0545
VL - 28
SP - 786
EP - 798
JO - Journal of the American Academy of Audiology
JF - Journal of the American Academy of Audiology
IS - 9
ER -