Figure 1. Drawing illustrates hearing aid function. Sound waves are amplified by the hearing aid (1). The tympanic membrane and ossicles convert the sound waves into mechanical energy (2). Pressure waves generated in the perilymphatic fluid pass from the scala vestibuli to the scala tympani (3). The hair cells in the organ of Corti convert this mechanical-pressure energy into an electrical impulse (4). The impulse travels through the spiral ganglia to the ventral and dorsal cochlear nuclei, located in the lateral brainstem adjacent to the foramen of Luschka (5). Crossed and uncrossed fibers carry the impulse through the lateral lemniscus, inferior colliculus, and medial geniculate body, and finally to the auditory cortex of the Heschl transverse temporal gyri (6).