The anatomy, physiology and disorders of the auditory cortex

The auditory cortex occupies a large proportion of the ventral bank of the lateral sulcus and superior temporal gyrus in humans and primates. In humans, this area includes the transverse temporal gyri of Heschl and the planum temporale, roughly corresponding to Brodmann's areas 41, 42, 52, and 22. One interesting structural feature of the cortex is that a central primary or core region lies adjacent to a number of secondary areas that forms a belt around the core. Many brain areas receive inputs from the cortex. These auditory-related regions are located in the temporal, parietal, and frontal lobes, and tend to feature multisensory convergence. Among species, the auditory cortex differs in relative position, arrangement, connections with other regional subdivisions, and tonotopic organization. The cortex is important in the processing of sounds used for communication. The human auditory cortex processes both elementary speech sounds and other temporally complex acoustic signals. Multisensory integration occurs in the cortex. Apart from auditory stimuli, accompanying visual and somatosensory signals assist in auditory perception. Cross-modal plasticity has been observed; the auditory area may be activated by visual or sign language in congenitally deaf adults Damage to the auditory cortex causes cortical deafness, pure word and auditory sound agnosia, and sensory amusia, depending on the extent of the auditory system lesion and other clinical characteristics. In patients with auditory hallucinations or subjective chronic tinnitus, functional magnetic resonance imaging has shown that the auditory cortex is active.