Angular gyrus (brain) related to language (i.e. reading, writing and interpretation of what is written), number processing and spatial cognition, memory retrieval, attention, and theory of mind.
An Angular gyrus or cerebral convolution is an area of the cerebral cortex in our brain, made up of many folds. There are many gyruses in the cerebral cortex.
It is more precisely located within the lower parietal lobe.
The frontal side (frontal) is bounded by the supramarginal gyrus (Brodmann area 40), the superior temporal gyrus and the medius temporal gyrus, occipital (rear) by the tertiary visual cortex (Brodmann area 19) and towards the vertex by the parietal lobule inferior.
The left and right angular gyrus are connected with the dorsal splenium and the isthmus of the corpus callosum. Both are located between the convolutions of the four lobes.
Connections with the angular gyrus
|Ipsilateral frontal region and the lower frontal and prefrontal regions.
|Superior longitudinal arched fascicle
|Inferior occipitofrontal fascicle
|Parahippocampal gyrus and hippocampus
|Inferior longitudinal fascicle
|Precuneus and superior frontal gyrus
It is supplied by the angular gyrus artery and a terminal branch of the posterior parietal artery, both branches of the middle cerebral artery. The (rare) isolated infarction of these blood vessels leads to the so-called angularis syndrome . Bleeding, tumors, inflammation, injuries and similar damage can also be the cause.
It belongs to the higher association areas of the cerebral cortex. It plays a decisive role in the networking of higher visual and hearing centers with higher sensory and motor areas.
Language and speeech functions
Precisely it is the part of the brain associated with complex language functions (i.e. reading, writing and interpreting what is written). The lesion of this part of the brain shows symptoms of Gerstmann syndrome: effects include agnosia of the fingers, alexia (inability to read), acalculia (inability to use arithmetic operations), agraphia (inability to read), to copy) and left-right confusion.
Its strategic position means that it associates with other areas of speech (in particular the supramarginal gyrus) to form – via neural networks – a multimodal region receiving stimuli that are both auditory, visual and somatosensory. Consequently, the GA constitutes a real engine of interpretation and processing of the phonological and semantic aspects of language.
Network in default mode
It is part of the default mode network, a network of brain regions activated during multimodal activities independent of external stimuli.
It reacts differently to intended and subsequent movement. This suggests that it is monitoring the intended movements of the ego and using the added information to calculate differently as it does for consecutive movements. By registering the deviation, the angular gyrus maintains self-awareness.
Activation of the angular gyrus shows that it not only mediates memory recovery, but also notes contradictions between what is expected of recovery and what is unusual. It can access both content and episodic memories and is useful in inferring the intentions of human characters. It can use a feedback strategy to determine whether recovery is expected or unusual.
Experiences outside the body
Recent experiments have demonstrated the possibility that stimulation of the right angular gyrus is the cause of out-of-body experiences. Stimulation of the left angular gyrus in one experiment caused a woman to perceive a dark person hiding behind her. The dark figure is actually a self-perceived double. Another such experiment made the test subject feel like he was on the ceiling. This is attributed to a divergence in the actual position of the body and the location perceived by the spirit of the body.
If angular gyrus damage
Damage to the angular gyrus manifests as Gerstmann syndrome. Damage may impair one or more of the below functions:
- Dysgraphia/agraphia: deficiency in the ability to write.
- Dyscalculia/acalculia: difficulty in learning or comprehending mathematics.
- Finger agnosia: inability to distinguish the fingers on the hand.
- Left-right disorientation.