Summary of the science: 1. Hearing loss is usually caused by damage and death of the hair cells——the sensory receptor cells that respond directly to sound. The

Summary of the science: 1. Hearing loss is usually caused by damage and death of the hair cells——the sensory receptor cells that respond directly to sound. The hairs on the upper face of these cells vibratethis physically opens ion channels that change the voltage across the cell membrane. This in turn causes these cell to releases neurotransmitters at their feet. The transmitter release then induces series of action potentials (spikes) in the axons of spiral ganglion cell; #2 below 2. But hearing loss can also be caused by damage to the spiral ganglion cells themselves. These cells and their axons conduct spikes between cochlea and brain. They cells are heavy workers and they are also fussy and metabolically demanding cells—-even by CNS standards. Revving them too high can blow their gaskets. In sum, two among several mechanisms that contribute to hearing loss and tinnitus. In a very similar way, blindness can also be caused by two major classes of cell damage and death—-1. the death of photoreceptors (called retinal degeneration) or 2. by damage to axons in the optic nerve (retinal ganglion cell axons). This is usually called glaucoma. This lovely study from Maison and colleagues is focused on the consequences of hearing loss caused primarily by damage to cochlear nerve fibers and their synapses in the cochlea, not the degeneration of hair cells per se. It is a systematic and rigorous study that supports the idea that tinnitus can be associated with nerve damage rather than hair cell loss. This is a surprisingly hard problem to nail down. If you want a good introduction to this work then read this review article by the same group. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5438769/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5438769/