Electrophysiological Estimates of the Electrode-Neuron Interface Differ Between Younger and Older Listeners With Cochlear Implants.
Kelly N Jahn, Julie G Arenberg
PMID 32032228WHAT IT FOUND
Cochlear implant users implanted in childhood had larger evoked nerve responses and steeper response growth than users implanted in adulthood.
Response thresholds did not differ, and these measures did not predict vowel recognition. This is an electrophysiological finding, not evidence for a programming change.
Key findings
01ECAP amplitudes and AGF linear slopes were significantly larger and steeper in the child-implanted group than in the adult-implanted group.
02ECAP thresholds did not differ significantly between groups, and interphase gap sensitivity did not differ between groups for slope or threshold.
03ECAP measures did not significantly predict vowel recognition scores.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Only 22 ears from 18 people were tested, so the findings are based on a small sample. The child-implanted and adult-implanted groups differed in chronological age, age at implantation, and duration of hearing loss, so the study cannot separate which of these factors relates to the ECAP differences. The study did not measure spiral ganglion neuron density directly; it inferred possible neural differences from ECAP responses and prior animal work. ECAP responses varied widely, especially within the child-implanted group, and most participants did not know the cause of their hearing loss. Five ears had only 2 or 3 usable amplitude growth functions, which limited some analyses. The planned interphase gap effect for AGF linear slope was not observed, so slope-based interphase gap sensitivity was inconclusive. Speech perception was tested with closed-set vowels only, and ECAP measures did not predict scores, so the link to functional hearing is limited.
Declared interests
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The easy way to misread this
Do not conclude that child-implanted users have denser spiral ganglion neurons or that ECAP-based programming will improve speech. The study did not measure neuron density directly, and ECAP measures did not predict vowel recognition.