The precuneus is a square-shaped coil in the parietal lobe of the brain, near the juncture between the two hemispheres; it is sometimes called the quadrate lobe. It gets its name from its location just above the cuneate lobe. The precuneus is involved in episodic memory, visual-spatial abilities, and motor activity coordination strategies. Additionally, functions of the precuneus include self perception, consciousness, and the executive and working memory.
The precuneus is interconnected to a variety of areas of the brain, making it integral to neural networks throughout the brain and brain-stem systems. It is considered one of the observable hot spots in the brain. Interestingly, even when at rest, its higher cognitive processing exhibits the highest metabolic rates, consuming 35% more glucose than any other cortex in the brain consumes. Researchers have observed, too, that metabolism rates are suspended when the precuneus is busy at executive and perceptual cognition tasks.
The precuneus’s various functions inform complex behavior in humans. As it is the seat of self-awareness, it engages in the higher cognitive functions of source and episodic memory and mental imagery. The precuneus is responsible for allowing people to evaluate themselves, rating personality and physical traits. Its self-reflection allows comparisons to be made between the self and others, and informs societal behavior.
Motor strategies in the precuneus include visuo-spatial functioning, which occurs when individuals preview movements in imagery, drawing on past memories of movement and coordination. Mental imagery also aids in the ability to make judgments of others, suggesting when to demonstrate a sense of empathy or express forgiveness toward others. It has been noted in studies that when a patient is awakening from anesthesia, the capacity for consciousness makes the precuneus the first detectable brain activity in recovery. This area is sometimes referred to as the hub of resting consciousness, during which time no particular motor or sensory imagery is taking place, and the self is merely self-aware. There are differing opinions as to the nature of brain function during resting consciousness; however, it has been agreed that the high metabolic rate during this mode indicates some activity is transpiring.
Lack of proper function in the precuneus shows significant impairments in several disorders. Lack of good regional cerebral blood flow in the precuneus, clearly identified in medical tests, is said to be the basis of impaired memory in lupus patients. Early-onset Alzheimer’s is identified by medical tests that show precuneus atrophy, leading to memory and visual-spatial difficulties.
