superior temporal gyrus
The superior temporal gyrus forms the most superior part of the temporal lobe, and has a role in both verbal and non-verbal communication.
The superior temporal gyrus is situated at the topmost aspect of the temporal lobe, lying inferior to the lateral sulcus and superior to the superior temporal sulcus. It extends posteriorly from the temporal pole, ending at the temporoparietal junction, and blending with the angular gyrus and supramarginal gyrus of the inferior parietal lobule. The superior temporal gyrus is formed by Brodmann areas 22 and 42 (lies in the middle of area 22) .
The superior temporal gyrus receives blood from the middle cerebral artery via all four main temporal branches: the temporopolar artery; anterior temporal artery, middle temporal artery and posterior temporal artery .
Function in the superior temporal gyrus exhibits lateralization with each hemisphere subserving distinct functions:
- right rostral superior temporal gyrus acts as site of convergence and interface between dorsal and ventral visual streams contributing to processing of both object- and space-related information , and fMRI studies have identified a critical role of the right superior temporal gyrus in social perception (the processing of non-verbal social cues to assess the mental states of others)
- left posterior superior temporal gyrus mediates language processing and is involved in auditory short-term memory and both perception and production of speech although language perception appears to have a degree of bilaterality, particularly with respect to phonemic information)
Lesions in the right rostral superior temporal gyrus result in visuospatial neglect on the contralesional side and impaired motion perception in both hemifields while lesions in the middle superior temporal gyrus lead to impairment in exploratory visual search .
Lesions of the left posterior superior temporal gyrus produce impairments in receptive language and can also result in a conduction aphasia (characterized by paraphasia and anomia). Bilateral lesions of the superior temporal gyrus are known to result in pure word deafness .
The superior temporal gyrus also appears to play a role in the pathophysiology of autism:
- an MRI study identified statistically significant enlargement of the right superior temporal gyrus in autistic individuals and, taken together with a postmortem study reporting abnormal cortical structure in autistic individuals along with fMRI studies showing abnormal activity in the superior temporal gyrus, points to a possible structural cause for the impaired social interaction seen in autism
- impaired activation of the left superior temporal gyrus in response to auditory stimuli has been observed in fMRI studies of autistic individuals and a dissociation between superior temporal gyrus volume and receptive language function in these individuals has also been observed