Perineuronal nets in subcortical auditory nuclei of four rodent species with differing hearing ranges
Less research has been done involving PNs in subcortical areas. Subcortical PNs are especially associated with motor and auditory nuclei, although not exclusively (Seeger, Brauer, Härtig, & Brückner, 1994; Bertolotto, Manzardo, & Guglielmone, 1996; Sonntag, Blosa, Schmidt, Rübsamen, & Morawski, 2015). Neonatal conductive hearing loss affects PNs in several auditory brainstem nuclei of the superior olivary complex (SOC), and PNs develop in the medial nucleus of the trapezoid body (MNTB) coincident with the maturation of reliable fast spiking (Taschenberger & von Gersdorff, 2000; Myers, Ray, & Kulesza, 2012). Studies examining the function of PNs in the auditory brainstem (specifically the MNTB) have shown that PNs are important to proper spike timing and spike rate, which are in turn essential for encoding sound characteristics such as frequency, intensity, and location (Oertel, 1999; Eggermont, 2001; Blosa et al., 2015; Balmer, 2016). Even though the importance of PNs to auditory function seems clear, there are inconsistencies in the literature regarding PN distribution in the subcortical auditory system. For example, a study in rat found that PNs were more prominent in the cortical areas of the inferior colliculus (IC) and lacking in the central nucleus, while a study in guinea pig found that PNs were densest in the central nucleus (rat: Bertolotto et al., 1996; guinea pig: Foster, Mellott, & Schofield, 2014). This particular discrepancy may be due to a difference in PN distribution between these two species, or it could reflect differences in the methods employed to visualize PNs (an antibody stain in the first study, and a lectin stain in the second). Another point of uncertainty in the literature is whether PN staining varies along the tonotopic axes of auditory nuclei.