Figure 2.

Ribbon synaptic configuration in mature inner hair cells (IHCs). At the IHC modiolar side, presynaptic regions have larger ribbons (red) and display higher Ca²⁺ inputs (light blue). Afferent neurons have smaller diameters, higher-threshold (HT) sensitivity and lower spontaneous rate (LSR). At the pillar side, ribbons are smaller and Ca²⁺ influx appears more confined; afferents have larger diameter, low-threshold (LT) sensitivity, and higher spontaneous rate (HSR). (References for afferent and ribbon characteristics: Liberman 1980 and Liberman et al. 2011; for presynaptic Ca²⁺ influx: Meyer et al. 2009 and Wong et al. 2014.) (Image reprinted from Safieddine et al. 2012 with permission from Annual Review of Neuroscience © 2012.)