Fusiform gyrus: What is it? Anatomy, Function and Associated Neurological Phenomena

It is part of the temporal lobe and the occipital lobe in the Brodmann area 37.

The fusiform gyrus is also known as the discontinuous gyrus.

The fusiform gyrus lies between the lingual gyrus and the anterior parahippocampal gyrus, and the inferior temporal gyrus below.

Although the functionality of the fusiform gyrus is not fully understood, it has been linked to several neural pathways related to recognition. In addition, it has been linked to various neurological phenomena, such as synesthesia , dyslexia, and prosopagnosia.

Anatomy

Anatomically, the fusiform gyrus is the largest macroanatomic structure within the ventral temporal cortex, which primarily includes structures involved in high-level vision.

The term fusiform gyrus refers to the fact that the shape of the gyrus is wider at its center than at its ends. This term is based on Emil Huschke’s description of the gyrus in 1854.

The fusiform gyrus is located on the basal surface of the temporal and occipital lobes and is delineated by the collateral sulcus (CoS) and the occipitotemporal sulcus (OTS), respectively.

ETO separates the fusiform gyrus from the inferior temporal gyrus (located laterally to the fusiform gyrus) and CoS separates the fusiform gyrus from the parahippocampal gyrus (located medially to the fusiform gyrus).

The fusiform gyrus can be delineated laterally and medially as it is separated in its center by the relatively shallow medial fusiform sulcus (MFS).

Therefore, the lateral fusiform gyrus is delineated by the OTS laterally and the MFS medially. Similarly, the medial fusiform gyrus is delineated laterally by the SFM and the CoS medially.

Importantly, the median fusiform sulcus serves as a macroanatomic landmark for the fusiform face area (FFA), a functional subregion of the fusiform gyrus that is supposed to play a key role in facial processing.

Function

The exact functionality of the fusiform gyrus is still disputed, but there is relative consensus on its involvement in the following pathways:

Color information processing

In 2003, VS Ramachandran collaborated with scientists from the Salk Institute for Biological Studies to identify the potential role of the fusiform gyrus within the color processing pathway in the brain.

Examining the within-pathway relationship specifically in cases of synesthesia, Ramachandran found that synaesthetics on average have a higher density of fibers surrounding the angular gyrus.

The angular gyrus is involved in further color processing.

The fibers relay information from the fusiform gyrus to the angular gyrus to produce the association of colors and shapes in grapheme synesthesia.

Cross activation between the angular and fusiform gyrus has been observed in the average brain, implying that the fusiform gyrus communicates regularly with the visual pathway.

Facial and body recognition

Parts of the fusiform gyrus are critical for facial and body recognition.

Word recognition

Parts of the fusiform gyrus of the left hemisphere are believed to be used in word recognition.

Identification within the category

After further research by MIT scientists, it was concluded that both the left and right fusiform gyrus played different roles from each other, but were subsequently related to each other.

The left fusiform gyrus plays the role of recognizing “facial” features in objects that may or may not be real faces.

Whereas the right fusiform gyrus plays the role in determining whether the characteristic recognized as “face” is, in fact, or not a real face.

Associated neurological phenomena

The fusiform gyrus has been speculated to be associated with various neurological phenomena. Many are detailed below:

Prosopagnosia

Some researchers think that the fusiform gyrus may be related to the disorder known as prosopagnosia or ocular blindness.

Research has also shown that the fusiform face area, the area within the fusiform gyrus, is heavily involved in the perception of the face, but only for any generic identification within the category that is shown to be one of the functions. of the fusiform gyrus.

Fusiform gyrus abnormalities have also been associated with Williams syndrome .

The fusiform gyrus has also been involved in the perception of emotions in facial stimuli.

However, people with autism show little or no activation in the fusiform gyrus in response to seeing a human face.

Synesthesia

Recent research has seen activation of the fusiform gyrus during subjective perception of grapheme color in people with synesthesia.

The effect of the fusiform gyrus in the sense of grapheme seems somewhat clearer since the fusiform gyrus appears to play a key role in word recognition.

The connection to color may be due to cross-wiring from (being directly connected) to areas of the fusiform gyrus and other areas of the visual cortex associated with experiencing color.

Dyslexia

For those with dyslexia, the fusiform gyrus has been found to be poorly activated and has a reduced gray matter density.

Hallucinations in the face

Increased neurophysiological activity in the fusiform face area can produce face hallucinations, either realistic or cartoonish, as seen in Charles Bonnet syndrome, hypnagogic hallucinations, peduncular hallucinations, or drug-induced hallucinations.