MOC reflex’s speech-in-noise unmasking role remains unproven in humans

Evidence

The roles of the MOC reflex (MOCR) in hearing remain controversial (Guinan 2006 , 2010 ). The MOCR may be essential for normal development of cochlear active mechanical processes (Walsh et al. 1998 ), and/or to minimize deleterious effects of noise exposure on cochlear function (Maison et al. 2013 ). A more widely accepted role is that the MOCR possibly facilitates understanding speech in noisy environments. This idea is based on the fact that MOC efferent activation restores the dynamic range of auditory nerve fibre responses in noisy backgrounds to values observed in quiet (Fig. 5 in Guinan 2006 ), something that probably improves the neural coding of speech embedded in noise (Brown et al. 2010 ; Chintanpalli et al. 2012 ; Clark et al. 2012 ). The evidence in support for this unmasking role of the MOCR during natural listening is, however, still indirect (Kim et al. 2006 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 1942

Categorization

• QUESTION: What would a direct human test of MOCR speech unmasking look like, and what confounds limit current indirect evidence?