Impact of Aging and the Electrode-to-Neural Interface on Temporal Processing Ability in Cochlear-Implant Users: Gap Detection Thresholds.
Maureen J Shader, Sandra Gordon-Salant, Matthew J Goupell
PMID 32941111WHAT IT FOUND
In cochlear implant users, higher stimulation rates significantly improved gap detection thresholds.
Steeper neural response slopes predicted better gap detection in younger adults, but this association disappeared in middle-aged and older groups, likely because their neural slopes were uniformly shallow.
Key findings
01Gap detection thresholds significantly improved (decreased) at 4000 pulses per second compared to the 1000 pulses per second reference rate.
02In younger adults, steeper electrically evoked compound action potential (ECAP) slopes predicted better gap detection thresholds, but this relationship did not hold for middle-aged or older participants.
03Gap detection thresholds measured at the most basal electrode (Electrode 4) were approximately 30% higher (worse) than those at the reference mid-array electrode.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used direct electrical stimulation via a research processor, bypassing the patient's everyday clinical sound processor and its speech processing strategies. The lack of an age effect in older groups may be partly due to a 'floor effect' in the neural measure, as older participants had very limited variability in their ECAP slopes. Loudness was not balanced across the different stimulation rates, meaning slight differences in perceived loudness could have influenced the gap detection results.
Declared interests
Funding was provided by the National Institute on Aging and the National Institute on Deafness and Other Communication Disorders. The authors did not report conflicts of interest.
The easy way to misread this
Do not conclude that aging directly causes a decline in central temporal processing ability independent of peripheral nerve health. The study found no significant main effect of age once the peripheral nerve measure (ECAP slope) was accounted for, and the older participants' uniformly shallow ECAP slopes made it impossible to separate the effects of central aging from peripheral aging.