Supramarginal gyrus

Introduction

The supramarginal gyrus (SMG) is a region of the brain located in the parietal lobe, specifically in the inferior parietal lobule. It is situated anterior to the angular gyrus and posterior to the postcentral gyrus. The SMG plays a crucial role in various cognitive and sensory processes, including language perception, spatial awareness, and empathy.

Anatomy and Location

The supramarginal gyrus is part of the parietal lobe, which is one of the four major lobes of the cerebral cortex. The parietal lobe is located near the upper back area of the skull and is responsible for processing sensory information from various parts of the body. The SMG itself is positioned at the junction of the parietal, temporal, and frontal lobes, making it a critical hub for integrating sensory and cognitive information.

The SMG is bounded anteriorly by the postcentral gyrus, posteriorly by the angular gyrus, superiorly by the intraparietal sulcus, and inferiorly by the lateral sulcus (Sylvian fissure). This anatomical positioning allows it to interact with multiple cortical areas, facilitating its involvement in diverse functions.

Functional Connectivity

The supramarginal gyrus is highly interconnected with other brain regions, forming part of several neural networks. It has strong connections with the prefrontal cortex, temporal lobe, and occipital lobe. These connections enable the SMG to participate in a wide range of cognitive tasks, including:

**Language Processing:** The SMG is involved in phonological processing and is crucial for language comprehension and production. It works in conjunction with Broca's area and Wernicke's area to facilitate speech and language functions.
**Spatial Awareness:** The SMG contributes to spatial orientation and the perception of body position in space. It integrates sensory information to help individuals navigate their environment.
**Empathy and Social Cognition:** The SMG is implicated in the ability to understand and share the feelings of others. It plays a role in theory of mind, which is the capacity to attribute mental states to oneself and others.

Clinical Significance

Damage or dysfunction in the supramarginal gyrus can lead to various neurological and psychiatric conditions. Some of the notable conditions associated with SMG impairment include:

**Aphasia:** Lesions in the SMG can result in language deficits, particularly in phonological processing. This can manifest as difficulty in understanding or producing speech.
**Gerstmann Syndrome:** Damage to the left parietal lobe, including the SMG, can cause Gerstmann syndrome, characterized by finger agnosia, left-right disorientation, agraphia, and acalculia.
**Neglect Syndrome:** Lesions in the right SMG can lead to hemispatial neglect, where individuals fail to attend to stimuli on one side of their body or environment.
**Dyslexia:** Abnormalities in the SMG have been linked to dyslexia, a learning disorder that affects reading and writing abilities.

Research and Studies

Numerous studies have investigated the role of the supramarginal gyrus in various cognitive functions. Functional magnetic resonance imaging (fMRI) and other neuroimaging techniques have been used to explore its involvement in language, spatial processing, and social cognition. Some key findings include:

**Language Processing:** Research has shown that the SMG is activated during tasks that require phonological processing, such as reading and verbal working memory. It is also involved in the integration of auditory and visual information during language comprehension.
**Spatial Cognition:** Studies have demonstrated that the SMG is crucial for spatial attention and the perception of spatial relationships. It is activated during tasks that involve mental rotation and spatial navigation.
**Empathy and Social Cognition:** Neuroimaging studies have revealed that the SMG is involved in the processing of emotional and social information. It is activated when individuals engage in tasks that require understanding the emotions and intentions of others.

References

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