Fusiform gyrus

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The fusiform gyrus, also known as the lateral occipitotemporal gyrus is a structure that lies on the basal surface of the temporal and occipital lobes. It forms part of Brodmann area 37, along with the inferior and middle temporal gyri. As its name suggests, it is composed of a temporal or anterior portion (T4) and an occipital or posterior portion (O4). It is delineated medially by the collateral sulcus and laterally by the occipitotemporal sulcus .

The fusiform gyrus, should not be confused with the medial occipitotemporal gyrus, which also has two components, one temporal (parahippocampal gyrus) and the other occipital (lingual gyrus).

Relations

Relations of the two sections of the fusiform gyrus to adjacent structures are as follows:

  • temporal portion
    • the most anterior aspect usually lies at the level of the cerebral peduncles and is typically curved or pointed in shape
    • sits inferior to the parahippocampal gyrus and superior to the inferior temporal gyrus
  • occipital portion

Blood supply

Blood is supplied to the fusiform gyrus by the posterior temporal artery and the occipitotemporal arteries; branches of the posterior cerebral artery .

Function

The fusiform gyrus is primarily involved in the higher functions of vision. Several have been identified and a couple are linked with specific named areas of the fusiform gyrus:

  • the fusiform gyrus forms part of the ventral stream and plays a role in differentiating between different categories of objects; a degree of lateralization has been observed on functional MRI with greater activity in lateral regions for objects with greater similarity and increased medial activation for more dissimilar objects
  • the fusiform face area (FFA) located on the lateral aspect of the mid-fusiform gyrus is involved in the perception and recognition of faces including recognizing one's own face ; however, it appears that the FFA on its own is insufficient for facial recognition and a functioning network of face-sensitive regions, including the occipital face area (OFA), is required ; a body-selective region in the fusiform gyrus located close to the FFA that responds selectively to human bodies has also been identified in fMRI studies
  • the visual word form area (VWFA) is located in the left lateral fusiform gyrus and contributes to the recognition of visual words and reading. fMRI studies have shown increased activation in the VWFA as subjects learned to read

Related pathology

Lesions of the fusiform gyrus result in a visual agnosia for objects, prosopagnosia and pure alexia (the inability to read) .

The fusiform gyrus has also been implicated in the pathogenesis of synesthesia (a condition in which stimulation in one sensory modality results in a secondary experience in another sensory modality). Grapheme-color and tone-color synesthetes have been found on voxel-based morphometry to have increased grey matter volume in the left posterior fusiform gyrus and decreased grey matter volume in the left anterior fusiform gyrus .