The fusiform gyrus is a structure of the brain, in the form of a convolution , involved in different processes that have to do with visual processing, understanding the meaning of a written text or face recognition, among other functions.

As we shall see later, damage to this structure causes serious sensory-perceptive disturbances.

In this article we explain what the fusiform gyrus is, its location and structure, its functions and main areas, as well as the most common disorders related to damage to this brain structure.

What is the fusiform gyrus?

The fusiform gyrus is a convolution of the brain that is part of the temporal lobe and occipital lobe involved in aspects such as visual word and face recognition or category identification.

This convolution was first described in 1854 by the anatomist Emil Huschke , who labelled this structure with that name because it was wider in the middle than at its ends, with a shape similar to that of a spindle.

It should be noted that the cerebral cortex contains a multitude of convolutions and grooves that give this organ its characteristic wrinkled appearance, with which we are all familiar. These folds increase the total surface area of the brain, so that more neural nuclei can be grouped together and therefore the ability to process information is also increased.

Location and structure

At the neuroanatomical level, the fusiform gyrus is one of the largest structures inserted in the ventral temporal cortex. This cerebral gyrus is located on the basal surface of the temporal and occipital lobes, between the parahippocampal gyrus and the lingual gyrus (medially), and the inferior temporal gyrus (laterally).
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The fusiform gyrus is composed of two portions: an anterior temporal portion and a posterior occipital one . The most anterior part of its temporal portion is located near the cerebral peduncles and is usually curved or pointed, while the occipital portion is below the tongue gyrus.

The collateral groove separates the fusiform gyrus from the parahippocampal gyrus and the occipitotemporal groove separates it from the lower temporal gyrus. It should be noted that the fusiform gyrus is part of Brodmann area 37, along with the inferior and medial temporal gyrus.

Brodmann’s areas classify the different parts of the cerebral cortex according to their involvement in different cognitive and behavioral functions, forming a topographic map of the brain that helps neuroscience professionals to better understand the functioning of each brain structure.

Functions

The main function of the fusiform gyration involves the processing of visual information , including the identification and differentiation of objects. In addition to high-level visual processing, this brain structure is involved in cognitive processes such as memory, multisensory integration or perception.

With regard to language, this area of the brain is involved in aspects such as semantic categorization, word retrieval and generation, understanding of metaphors or the connection between orthographic and phonological components; at the level of memory processing, it is involved in the recognition of true and false memories, as well as spontaneous coding.

It is also believed that the fusiform gyration could have a close functional relationship with the angular gyration, as this structure is involved in the processing of colours. Fusiform gyrus communicates with the visual pathway and angular gyrus, which would allow the association of colors and shapes.

On the other hand, while the exact functional relevance of the fusiform gyrus remains unclear, it has been suggested that it may be involved in the following neurological systems related to the processing and recognition of visual information:

  • Color processing

  • Facial recognition

  • Body recognition

  • Word recognition

  • Identification of characteristics within categories

The fusiform area of the faces

The fusiform area of the faces is perhaps the best known structure in this region of the brain. It is found on the lateral surface of the mid-fusiform gyrus and plays a key role in face identification, including recognition of one’s own face.

Currently, there is an open debate in the neuroscientific community about whether this region is dedicated only to face processing or whether it is also involved in the recognition of other objects. One of the hypotheses (known as the experience hypothesis) suggests that this region would be important for discriminating and individualizing visually similar objects. For example, when a chess expert identifies a pawn or a queen.

One of the controversies surrounding this region arises from the observation that this area does not fully develop until adolescence, even though babies already show some ability to differentiate faces, like their mothers, and a preference for female faces. MRI studies have also not confirmed that this area participates in these functions.

However, the fusiform gyrus and fusiform area of the faces is not the only brain region that facilitates face identification. Although the fusiform area of the faces is an important component, it requires a network of different neuronal nuclei in the cortex capable of recognizing faces, including areas adjacent to the occipital lobe (the main area responsible for visual processing).

Related disorders

One of the best known disorders related to fusiform gyrus damage is prosopagnosia or visual blindness, a condition characterized by the inability to recognize familiar faces (including one’s own). This disorder may result from isolated lesions in the fusiform area of the fusiform gyrus faces.

It is known that other functions involved in visual processing, such as word processing, remain intact in patients with prosopagnosia; when this is acquired, it usually results from a lesion in the spindle gyrus and usually occurs in adults, whereas in congenital prosopagnosia the subject never develops the ability to recognize faces.

Another condition that can be caused by damage to structures related to the fusiform gyrus is synaesthesia, a neurological condition that causes stimulation of one sensory pathway to generate an involuntary experience in another sensory pathway, for example, seeing colors when certain sounds are heard.

The most common subtypes of synaesthesia include: colored grapheme, which consists of associating any sign or letters with a certain color; and colored music, when the individual sees several colors depending on the type of music he or she is listening to.

Finally, another condition that has been associated with decreased activation and lower density of fusiform gray matter is dyslexia, a disorder that causes confusion and impaired reading accuracy and fluency,

Bibliographic references:

  • McCarthy, G., Puce, A., Gore, J. C., & Allison, T. (1997). Face-specific processing in the human fusiform gyrus. Journal of cognitive neuroscience, 9(5), 605-610.

  • Snell, R. S. (2007). Clinical neuroanatomy. Panamerican Medical Ed.