auditory cortex

Meaning: The auditory cortex is the region of the temporal lobe that processes sound. Signals pass from the cochlea to brainstem nuclei, the inferior colliculus, and the medial geniculate nucleus of the thalamus before reaching it. Its layout is tonotopic: different sites respond to different pitches. Each ear sends input to both hemispheres, with a stronger projection to the opposite side.

On the MCAT: Expect questions matching each sense to its thalamic relay and lobe: vision uses the lateral geniculate nucleus and occipital lobe; hearing uses the medial geniculate nucleus and temporal lobe. Passages may describe a lesion or imaging study and ask what function is lost or which area is active when a subject hears tones. Wernicke's area, usually in the left temporal lobe, lies nearby and handles language comprehension.

Common confusion: The cortex does not detect sound. Hair cells in the cochlea transduce it, and the cortex interprets it. Also, damage to one auditory cortex does not usually make one ear deaf, because of the bilateral input; it tends to impair things like sound localization. Deafness from cortical damage generally requires both sides to be affected.