abnormal auditory brainstem response waveform shape abnormal auditory brainstem response wave amplitude 2025-07-21T11:43:09Z abnormal ABR wave amplitude MP:0031670 anomaly in the size (height or maximum displacement) of any of a series of auditory brainstem response waves, each of which is generated by specific groups of neurons along the ascending auditory pathway MPheno.ontology In mammals, the ABR includes 4 to 5 identifiable waves (typically labeled as waves I-V) which are stereotyped in their time course and reflect evoked activity in the auditory nerve and brainstem. The amplitude of each wave reflects the number of neurons firing synchronously in response to the auditory stimulus and represents the strength or magnitude of the waveform. Wave I is generated by the auditory nerve and spiral ganglion neurons. Wave II is driven mostly by the globular bushy cells in the cochlear nucleus. Wave III is generated partly by spherical cells from the cochlear nucleus and the medial superior olive. Wave IV is driven by projections from the lateral lemniscus to the inferior colliculus. Wave V is not always identifiable in mice, whereas in humans wave V is robust. In contrast, wave I is robust in mice but can be difficult to distinguish in humans. Biological factors that affect the ABR waveform include the species/strain, age, and sex of the individual. Among laboratory mice, strain differences are present in the amplitudes and latencies of waves I and IV, with significant differences in the wave I:IV amplitude ratio and I-IV interpeak latency across strains.