TY - JOUR
T1 - Spatial spread of neural excitation in cochlear implant recipients
T2 - Comparison of improved ECAP method and psychophysical forward masking
AU - Cohen, Lawrence T.
AU - Richardson, Louise M.
AU - Saunders, Elaine
AU - Cowan, Robert S C
PY - 2003/5
Y1 - 2003/5
N2 - This study introduces and evaluates a method for measurement of the longitudinal spread of electrically evoked neural excitation in the cochlea, using the Neural Response Telemetry™ system (NRT™) available with the Nucleus® 24 cochlear implant system. The recently released version of the NRT software (version 3.0) enables presentation of the 'masker' and 'probe' on different electrodes. In the present method the probe position was fixed, while the masker position was varied across the electrode array. The amplitude of the response to the partially masked probe provides a measure of the amount of masking, which is dependent on the extent of overlap of the excitation regions of the masker and probe. These measurements were performed in seven subjects implanted with the Nucleus 24 cochlear implant system (four with straight and three with Contour™ electrode arrays), for basal, middle and apical probe electrodes. Similar excitation profiles were obtained using either the standard NRT subtraction paradigm or an alternative 'Miller' method. The excitation profiles were compared with those obtained from psychophysical forward masking and good agreement was found. The widths of electrically evoked compound action potential (ECAP) and forward masking profiles did not differ significantly. Whereas the width of the ECAP measure was significantly correlated with both the maximum comfortable level and the distance of the electrode band from the modiolus, the width of the forward masking profile was not.
AB - This study introduces and evaluates a method for measurement of the longitudinal spread of electrically evoked neural excitation in the cochlea, using the Neural Response Telemetry™ system (NRT™) available with the Nucleus® 24 cochlear implant system. The recently released version of the NRT software (version 3.0) enables presentation of the 'masker' and 'probe' on different electrodes. In the present method the probe position was fixed, while the masker position was varied across the electrode array. The amplitude of the response to the partially masked probe provides a measure of the amount of masking, which is dependent on the extent of overlap of the excitation regions of the masker and probe. These measurements were performed in seven subjects implanted with the Nucleus 24 cochlear implant system (four with straight and three with Contour™ electrode arrays), for basal, middle and apical probe electrodes. Similar excitation profiles were obtained using either the standard NRT subtraction paradigm or an alternative 'Miller' method. The excitation profiles were compared with those obtained from psychophysical forward masking and good agreement was found. The widths of electrically evoked compound action potential (ECAP) and forward masking profiles did not differ significantly. Whereas the width of the ECAP measure was significantly correlated with both the maximum comfortable level and the distance of the electrode band from the modiolus, the width of the forward masking profile was not.
KW - Cochlear implant
KW - Electrically evoked compound action potential
KW - Forward masking
KW - Neural response telemetry
KW - Spread of neural excitation
UR - http://www.scopus.com/inward/record.url?scp=0038299943&partnerID=8YFLogxK
U2 - 10.1016/S0378-5955(03)00096-0
DO - 10.1016/S0378-5955(03)00096-0
M3 - Article
C2 - 12742240
AN - SCOPUS:0038299943
SN - 0378-5955
VL - 179
SP - 72
EP - 87
JO - Hearing Research
JF - Hearing Research
IS - 1-2
ER -