Widened cochlear filters preserve envelope modulation while CI electrode spread does not

Evidence

On one hand, cochlear hearing loss is generally accompanied by a loss of frequency selectivity, due to loss of function of the outer hair cells; on the other hand this “smearing” of the spectrum occurs before extraction of the temporal envelope, rather than afterwards, as is the case with CI processing. Because the smearing is due to wider filters, rather than envelope summation, the resultant envelopes from broader filters still have Rayleigh-distributed envelopes with the same overall relative modulation power as the envelopes from narrower filters (i.e., the same area under the modulation power spectrum, normalized to DC; see Fig. 1 ). In contrast, with CIs, the envelopes derived from summing the envelope currents from adjacent electrodes are no longer Rayleigh distributed and have lower modulation power, relative to the overall (DC) power in the envelope (Hu and Beaulieu 2005 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 2167

Categorization

• DEEPTHINKING: A precise mechanistic distinction: sensorineural hearing loss widens filters before envelope extraction (preserving Rayleigh statistics and total modulation power), while CIs sum envelopes after extraction (breaking Rayleigh statistics and cutting relative modulation) — two superficially similar degradations that differ in exact transform of the signal.
• corroborated: 2 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 2167
• XREF: connects to: Broader cochlear filters preserve envelope modulation power while electrode summation in CIs reduces it; Broader cochlear filters shift noise modulation power away from speech-relevant low frequencies; Broader cochlear filtering reduces low-frequency noise fluctuations, explaining lost masking release — Dijk, Pim van, Physiology, Psychoacoustics and…, 2161 (+1 more)

Broader Connections

• Broader cochlear filters preserve envelope modulation power while electrode summation in CIs reduces it #expands (0.95)
• Deactivating multiple cochlear implant electrodes can worsen spectral precision by broadening analysis bands #expands (0.85)
• Broader cochlear filters shift noise modulation power away from speech-relevant low frequencies #expands (0.80)
• Broader cochlear filtering reduces low-frequency noise fluctuations, explaining lost masking release #expands (0.80) — Dijk, Pim van, Physiology, Psychoacoustics and…, 2161