Our results partially correspond to results of a previous study showing that age-related hearing loss involved neurodegeneration of SGNs with accumulation of lipofuscin granules in SAMP8 mice34, while a previous study has shown Mn-mediated aggregation of alpha-synuclein in the frontal cortex in non-human primates injected with manganese sulfate (MnSO4) at 3.3–10.0 mg/kg/week for maximum 52 weeks35. The gene discussed is SNCA; the disease is presbycusis.