title: Effects of stimulus level and rate on psychophysical thresholds for interleaved pulse trains in cochlear implants.
abstract: This study examined channel interactions using interleaved pulse trains to assess masking and potential facilitative effects in cochlear-implant recipients using clinically relevant stimuli. Psychophysical thresholds were measured for two adjacent mid-array electrodes; one served as the masker and the other as the probe. Two rates representative of those found in present-day strategies were tested: 1700 and 3400 pulses per second per channel. Four masker levels ranging from sub-threshold to loud-but-comfortable were tested. It was hypothesized that low-level maskers would produce facilitative effects, shifting to masking effects at high levels, and that faster rates would yield smaller masking effects due to greater stochastic neural firing patterns. Twenty-nine ears with Cochlear or Advanced Bionics devices were tested. High-level maskers produced more masking than low-level maskers, as expected. Facilitation was not observed for sub-threshold or threshold-level maskers in most cases. High masker levels yielded reduced probe thresholds for two Advanced Bionics subjects. This was partly eliminated with a longer temporal offset between each masker-probe pulse pair, as was used with Cochlear subjects. These findings support the use of temporal gaps between stimulation of subsequent electrodes to reduce channel interactions.
authors: Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131, USA.
authors: Michelle L
authors: ML
authors: Hughes
authors: Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131, USA.
authors: Jenny L
authors: JL
authors: Goehring
authors: Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131, USA.
authors: Jacquelyn L
authors: JL
authors: Baudhuin
authors: Department of Biostatistics, 984375 University of Nebraska Medical Center, Omaha, Nebraska 68198-4375, USA.
authors: Kendra K
authors: KK
authors: Schmid
mesh_terms: D001309:Auditory Threshold; D003051:Cochlea; D019929:Cochlear Implantation; D003054:Cochlear Implants; D010470:Perceptual Masking