The angular gyrus is a significant region of the human brain involved in complex cognitive processes. It functions as an integration hub, connecting various brain areas to process different types of information. This enables higher-level thought and understanding.
Anatomy of the Angular Gyrus
The angular gyrus is located within the inferior parietal lobule of the parietal lobe. It is situated near the superior edge of the temporal lobe and the posterior end of the lateral sulcus, between the parietal, occipital, and temporal lobes. This horseshoe-shaped structure caps the angular sulcus, a continuation of the superior temporal sulcus.
The angular gyrus is also known as Brodmann area 39. The two angular gyri, one in each hemisphere, are connected by the dorsal splenium and isthmus of the corpus callosum. Its blood supply comes from the middle cerebral artery.
Diverse Functions of the Angular Gyrus
The angular gyrus contributes to a range of cognitive functions, integrating information from different brain regions. It is involved in complex language processing, including reading, writing, and interpreting written words. This region helps transfer visual information to Wernicke’s area for understanding visually perceived words.
The angular gyrus also plays a part in numerical cognition, including arithmetic and understanding quantities. Brain injuries to this area have been linked to arithmetic deficits. The left angular gyrus, along with the left inferior frontal gyrus, supports exact calculations by retrieving verbal arithmetic facts. Its activity level correlates with an individual’s arithmetic skills.
Spatial awareness and navigation also involve the angular gyrus. It contributes to perceiving and understanding space, allowing for environmental orientation and coordinated movements. The right angular gyrus is associated with directing spatiovisual attention toward important features.
For body image and self-perception, the angular gyrus assists in distinguishing left from right, integrating conceptual understanding with spatial location. It is also linked to orienting in three-dimensional space, potentially by controlling attention shifts. Memory retrieval, especially semantic memory, is another function attributed to this region.
The angular gyrus is also implicated in social cognition and theory of mind, the ability to understand and attribute mental states. This broad involvement across multiple cognitive domains highlights its role as a central hub for information integration.
Impact of Angular Gyrus Impairment
Damage or dysfunction of the angular gyrus can lead to specific cognitive deficits. One notable consequence is Gerstmann’s Syndrome, a condition characterized by a cluster of symptoms: agraphia (difficulty writing), acalculia (difficulty with arithmetic), finger agnosia (inability to recognize or name individual fingers), and left-right disorientation. This syndrome can also result from damage to the fusiform gyrus.
Individuals with angular gyrus impairment may also experience isolated difficulties such as alexia (inability to read), agraphia, or acalculia. Anomia (difficulty naming objects) can also occur. Certain types of apraxia (difficulty with skilled movements) have been associated with damage to this region.
Common causes of impairment include strokes, traumatic brain injuries, and neurodegenerative diseases. The precise symptoms and their severity depend on the exact location and extent of the damage within the angular gyrus. Reduced activity in the angular gyrus is observed in individuals with dyslexia, aligning with difficulties in spelling, reading, and writing.