The term “supratentorial brain” describes a specific, large division of the human brain positioned in the upper portion of the skull. This region is responsible for the most complex aspects of human existence, including thought, memory, and voluntary action. The structures located here regulate nearly all conscious and many unconscious functions that allow a person to interact with their environment. Understanding this anatomical boundary is helpful for localizing diseases or injuries within the central nervous system.
Anatomical Definition and Location
The separation between the upper and lower parts of the brain is created by a distinct anatomical partition called the tentorium cerebelli. This structure is a dense, sheet-like fold of the dura mater, the tough, outermost membrane covering the brain and spinal cord. The tentorium cerebelli stretches across the cranial cavity, functioning like a physical roof over the cerebellum and the space below it.
The entire area situated above this dural partition is defined as the supratentorial region, while the space beneath it is referred to as the infratentorial region. This anatomical division creates two distinct compartments within the skull, with the tentorium serving as the dividing line between the forebrain and the hindbrain structures. The term supratentorial is therefore purely a spatial designation, indicating a location relative to this specific dural fold.
Key Structures Housed Above the Tentorium
The supratentorial space contains the largest part of the central nervous system, including the extensive cerebral hemispheres. These two hemispheres, the left and the right, are covered by the convoluted cerebral cortex and contain the vast majority of the brain’s neurons. Beneath the hemispheres lie important subcortical components, forming the deepest parts of the supratentorial mass.
One significant deep structure is the thalamus, which serves as a central hub for relaying sensory and motor signals to the cerebral cortex. The basal ganglia are another collection of deep nuclei situated within this upper region. These clusters of gray matter manage motion control and procedural learning pathways. The supratentorial area also includes the ventricular system, which produces and circulates cerebrospinal fluid.
Essential Functions of the Supratentorial Region
The structures contained within the supratentorial compartment are responsible for coordinating the most advanced human capabilities, often referred to as higher cognitive processes. These abilities include language comprehension and production, abstract reasoning, and the formation and retrieval of complex memories. The cerebral cortex, in particular, manages awareness, personality, and the ability to plan and execute complex tasks.
Movement control originates here through pathways involving the cerebral cortex and the basal ganglia. Signals are generated in the motor cortex and refined by the deep gray matter nuclei, allowing for coordinated, voluntary motion.
The supratentorial region handles sensory integration, processing raw input from the eyes, ears, and skin into a unified perception of the world. The thalamus filters and routes incoming sensory data to the appropriate cortical areas for processing.
Clinical Significance of Supratentorial Issues
Pathologies in the supratentorial region typically present with a unique set of symptoms compared to those in the lower brain. One common issue is a stroke, which occurs when blood flow to a portion of the cerebrum is interrupted, either by a blockage (ischemic stroke) or bleeding (hemodynamic stroke). Damage from a supratentorial stroke often results in profound focal neurological deficits, such as hemiparesis (paralysis on one side of the body) or aphasia (difficulty with language).
Tumors are another serious concern, with the majority of primary central nervous system tumors in adults developing in the supratentorial space, such as gliomas and meningiomas. The presentation of a tumor depends on its exact location; for example, a tumor near the visual cortex in the occipital lobe may cause visual field loss. As these masses grow, they increase intracranial pressure, leading to generalized symptoms like headache, nausea, and vomiting. Cognitive impairment, including issues with attention, memory, and executive function, is also a common result of damage to these extensive neural networks.