Effects of pulse separation on detection thresholds for electrical stimulation of the human cochlea

• Published in: Hearing research 1996-09, Vol.98 (1), p.77-92
• Main Authors: Pfingst, Bryan E., Holloway, Lisa A., Razzaque, Sharif A.
• Format: Article
• Language: English
• Subjects: Adult; African Continental Ancestry Group; Aged; Auditory Threshold - physiology; Biological and medical sciences; Cochlea - physiology; Cochlear implant; Cochlear Implants - standards; Cohort Studies; Deafness - physiopathology; Detection threshold; Ear, auditive nerve, cochleovestibular tract, facial nerve: diseases, semeiology; Electric Stimulation; Electrical stimulation; European Continental Ancestry Group; Female; Hispanic Americans; Human; Humans; Male; Medical sciences; Middle Aged; Non tumoral diseases; Otorhinolaryngology. Stomatology; Psychophysics; Pulse separation; Speech Reception Threshold Test
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/0378-5955(96)00071-8

Effects of pulse separation on detection of electrical stimulation of the cochlea were studied in 12 profoundly deaf human subjects with Nucleus 22 cochlear implants. Biphasic symmetric pulses were used. Pulse separation is the time from offset of one biphasic pulse to the onset of the next biphasic pulse in the train. Effects of pulse separation were studied in the context of different covariables in four stages of the experiment. Effects of pulse separation seen in the different stages were similar, despite the different covariables. Both pulse separation and the total number of pulses per stimulus seem to be important variables affecting stimulus detection. For 0.5 ms/phase pulses, thresholds were lowest at the shortest pulse separations tested (0.2–1.1 ms) and increased as a function of pulse separation. For 2 ms/phase pulses, detection thresholds were lowest at pulse separations around 7.5 ms, in most cases, and higher at both longer and shorter pulse separations. These results suggest that interactions among adjacent pulses can either hinder or facilitate detection of the signal depending on the magnitudes of pulse separation and phase duration. Pulse separations at which thresholds measured for 2 ms/phase pulses were minimum were fairly consistent across subjects and did not correlate well with speech recognition scores. However, significant variation in this measure across species has been seen.