Fusiform gyrus
The fusiform gyrus is part of the temporal lobe and occipital lobe in Brodmann area 37. It is also known as the (discontinuous) occipitotemporal gyrus.
The fusiform gyrus is located between the inferior temporal gyrus and the parahippocampal gyrus.
The lateral and medial portions are separated by the shallow mid-fusiform sulcus.
The paramedian supracerebellar transtentorial approach (PST) provides the surgeon precise anatomical orientation when exposing the entire length of the mediobasal temporal region (MTR), as well as the fusiform gyrus, for removing any lesion 1).
Areas
The fusiform face area (FFA) is a part of the human visual system that, it is speculated, is specialized for facial recognition, although there is some evidence that it also processes categorical information about other objects, in particular familiar ones. It is located in the fusiform gyrus (Brodmann area 37).
The FFA is located in the ventral stream on the ventral surface of the temporal lobe on the lateral side of the fusiform gyrus. It is lateral to the parahippocampal place area. It displays some lateralization, usually being larger in the right hemisphere.
Functionality
The specific brain area usually associated with prosopagnosia is the fusiform gyrus, which activates specifically in response to faces. The functionality of the fusiform gyrus allows most people to recognize faces in more detail than they do similarly complex inanimate objects. For those with prosopagnosia, the new method for recognizing faces depends on the less-sensitive object recognition system. The right hemisphere fusiform gyrus is more often involved in familiar face recognition than the left. It remains unclear whether the fusiform gyrus is only specific for the recognition of human faces or if it is also involved in highly trained visual stimuli.
A patient with paroxysmal aphasia evoked by ictal epileptiform discharges localized to the left fusiform gyrus, where a small brain tumor existed. The intracranial EEG recordings during other seizures demonstrated a close functional link between the left fusiform gyrus and Wernicke's area. The patient also showed transient aphasia with electrical stimulation of the left fusiform gyrus 2).
There is still some dispute over the functionalities of this area, but there is relative consensus on the following:
processing of color information
face and body recognition (see Fusiform face area)
word recognition (see Visual word form area)
within-category identification
Some researchers think that the fusiform gyrus may be related to the disorder known as prosopagnosia, or face blindness. Research has also shown that the fusiform face area, the area within the fusiform gyrus, is heavily involved in face perception but only to any generic within-category identification that is shown to be one of the functions of the fusiform gyrus.
Abnormalities of the fusiform gyrus have also been linked to Williams syndrome.
Fusiform gyrus has also been involved in the perception of emotions in facial stimuli.
However, individuals with autism show little to no activation in the fusiform gyrus in response to seeing a human face
Increased neurophysiological activity in the fusiform face area may produce hallucinations of faces, whether realistic or cartoonesque, as seen in Charles Bonnet syndrome, hypnagogic hallucinations, peduncular hallucinations, or drug-induced hallucinations.
Recent research has seen activation of the fusiform gyrus during subjective grapheme-color perception in people with synaesthesia.
After further research by scientists at MIT, it was concluded that both the left and right fusiform gyrus played different roles from one another, but were subsequently interlinked. The left fusiform gyrus plays the role of recognizing “face-like” features in objects that may or may not be actual faces. Whereas the right fusiform gyrus plays the role in determining whether or not the recognized “face-like” feature is, in fact, an actual face.
Operations on tumors of the posteromedial temporal region, that is, on those arising from the fusiform gyrus, are challenging to perform because of the deep-seated location of these tumors between critical cisternal neurovascular structures and the adjacent temporal and occipital cortexes.
Tumors of the fusiform gyrus generated a superior (and lateral) shift; consequently, a subtemporal approach is recommended to avoid white matter injury 3).