Cochlear implant growth functions can behave non-monotonically near the top of the dynamic range
Evidence
Closer inspection of the data revealed that the input/output growth functions sometimes had non-monotonic shapes. An example obtained for G7 1 month after deafening is illustrated in Fig. 4c for RPS-A and RPS-C. The function for RPS-C shows, at some point in the dynamic range, a decrease in response amplitude with increases in level. In this case, the cathodic pulse was more effective than the anodic pulse at low levels but less effective at high levels. — Dijk, Pim van, Physiology, Psychoacoustics and…, 2309
Categorization
- SEED: The finding that one polarity can be more effective at low levels yet less effective at high levels is a striking counterintuitive result — the polarity-dependence of recruitment is level-dependent, a nuance that complicates any clinical strategy keyed to a single polarity preference.
- QUESTION: What neural mechanism makes a cathodic pulse more effective at low levels but less effective at high levels? Could involve two different fiber populations (central vs peripheral processes) with different thresholds.
- corroborated: 3 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 2309
- XREF: connects to: Cochlear implant input-output responses can reverse polarity preference at high levels; Action potential blocking can make louder cochlear implant stimuli evoke smaller responses