Corticofugal modulation of audition

Direct cochlear recordings in humans show a theta rhythmic modulation of the auditory nerve by selective attention

“…The efferent auditory system comprises a complex arrangement of subcortical and peripheral pathways where – uniquely among the senses – the cochlear activity can be altered by top-down signals from the auditory cortex via the SOC (Chandrasekaran & Kraus, 2010; Elgueda & Delano, 2020; Suga, 2008; Terreros & Delano, 2015; Winer, 2006). Profound evidence supports the notion of altered oscillatory neural activity by selective attention on a cortical level (Frey et al, 2014; Haegens et al, 2011; Handel et al, 2010; Mazaheri et al, 2014; Salo et al, 2017; Weise et al, 2016), prioritizing attended over unattended events in the environment which is predominantly reflected in modulations within the alpha band (~9-13 Hz; Frey et al, 2014; Sauseng et al, 2005; for a review see Foxe & Snyder, 2011; notably also Antonov et al, 2020 that challenges current views).…”

“…While such changes have also been reported for the auditory cortex (Weisz et al, 2011), much less is known for subcortical structures along the efferent pathway. This is in particular the case when it comes to the human cochlea as special recording and analysis techniques are required (Elgueda & Delano, 2020). So far, investigating attentional modulation of cochlear activity in humans had to rely on indirect recordings of OAEs; a noninvasive approach for measuring OHC activity that receives modulatory signals from the SOC through its medial neurons (MOC).…”

“…Activity of OHCs are modulated by a pathway from the medial olivocochlear (MOC) system that itself originates in the superior olivary complex (SOC). Spiral ganglion cells making up the auditory-nerve fibers are mainly innervated by connections of the lateral olivocochlear complex (LOC) respectively (Elgueda & Delano, 2020;Warr & Guinan, 1979). Attentional modulations of OAEs can thus be seen as a proxy for subcortical attentional modulations and have been reported for either attending the left or the right ear (Giard et al, 1994) when one out of two frequencies was task relevant (Maison et al, 2001) or attention had to be focused on the visual or auditory modality (Dragicevic et al, 2019;Wittekindt et al, 2014).…”

“…However, in contrast to e.g. the visual modality, the auditory system comprises a unique complex network of subcortical regions which all receive structural top-down connections originating in the auditory cortex (Chandrasekaran & Kraus, 2010; Elgueda & Delano, 2020; Suga, 2008; Terreros & Delano, 2015; Winer, 2006). By the most direct path, top-down information can reach the cochlea via only one extra relay through the superior olivary complex (SOC).…”

“…Thus, cochlear activity can in principle be altered by top-down signals from the auditory cortex. However, studying peripheral auditory functioning requires special recording and analysis techniques (Elgueda & Delano, 2020) and has therefore been rarely investigated in this regard.…”