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The brain has a unique appearance that consists of many ridges and indentations. A brain ridge is known as a gyrus (plural: gyri) and an indentation or depression is a sulcus (plural: sulci) or fissure. Gyri and sulci give the brain its wrinkled appearance.
The cerebral cortex, or the outer layer of the cerebrum, consists of gyri that are typically surrounded by one or more sulci. The cerebral cortex is the most highly developed area of the brain and is responsible for higher brain functions such as thinking, planning, and decision making.
Key Takeaways: Brain Gyri and Sulci
- Gyri and sulci are the folds and indentations in the brain that give it its wrinkled appearance.
- Gyri (singular: gyrus) are the folds or bumps in the brain and sulci (singular: sulcus) are the indentations or grooves.
- Folding of the cerebral cortex creates gyri and sulci which separate brain regions and increase the brain's surface area and cognitive ability.
- Gyri and sulci form boundaries within and between the lobes of the brain and divide it into two hemispheres.
- The medial longitudinal fissure is the sulcus that separates the left and right brain hemispheres. The corpus callosum is found within this fissure.
- An example of a gyrus is Broca's gyrus, an area of the brain that orchestrates speech production.
Gyri and Sulci Functions
Brain gyri and sulci serve two very important functions: They increase the surface area of the cerebral cortex and they form brain divisions. Increasing the surface area of the brain allows more neurons to be packed into the cortex so that it can process more information. Gyri and sulci form brain divisions by creating boundaries between the lobes of the brain and dividing the brain into two hemispheres.
Lobes of the Cerebral Cortex
The cerebral cortex is divided into the following four lobes that each serve several important functions.
- Frontal lobes: The frontal lobes are located in the front-most region of the cerebral cortex. They are vital for motor control, thinking, and reasoning.
- Parietal lobes: The parietal lobes are positioned above the temporal lobes near the brain's center and they process sensory information.
- Temporal lobes: The temporal lobes are positioned behind the frontal lobes. They are important for language and speech production as well as memory and emotion processing.
- Occipital lobes: The occipital lobes sit at the posterior region of the cerebral cortex and are the main centers for visual processing.
Gyri and sulci are very important features of the central nervous system. Folding of the cerebral cortex creates these ridges and grooves which serve to separate brain regions and increase cognitive ability.
Brain Sulci or Fissures
Below is a listing of several key sulci/fissures in the brain and the divisions they create.
- Interhemispheric (Medial Longitudinal Fissure): This is a deep furrow located down the center of the brain that separates the left and right brain hemispheres. The corpus callosum, a wide ribbon of nerves, is located within this fissure.
- Fissure of Sylvius (Lateral Sulcus): This deep grove separates the parietal and temporal lobes.
- Central Sulcus (Fissure of Rolando): This sulcus separates the parietal and frontal lobes.
- Collateral Sulcus: This furrow separates the fusiform gyrus and the hippocampal gyrus on the lower surface of the temporal lobes.
- Parieto-occipital Sulcus: This deep crevice separates the parietal and occipital lobes.
- Calcarine Sulcus: This groove is located in the occipital lobes and divides the visual cortex.
Listed below are a number of important gyri of the cerebrum.
- Angular Gyrus: This fold in the parietal lobe is the area of the brain that assists in processing auditory and visual stimuli. It is also involved in language comprehension.
- Broca's Gyrus (Broca's Area): This area of the brain, located in the left frontal lobe in most individuals, controls motor functions involved with speech production.
- Cingulate Gyrus: This arch-shaped fold in the brain is located above the corpus callosum. It is a component of the limbic system that processes sensory input concerning emotions and regulates aggressive behavior.
- Fusiform Gyrus: This bulge, located in the temporal and occipital lobes, consists of lateral and medial parts. It is thought to play a role in facial and word recognition.
- Hippocampal Gyrus (Parahippocampal Gyrus): This fold on the inner surface of the temporal lobe borders the hippocampus. The hippocampal gyrus surrounds the hippocampus and plays an important role in memory.
- Lingual Gyrus: This coil of the occipital lobe is involved in visual processing. The lingual gyrus is bordered by the calcarine sulcus and collateral sulcus. Anteriorly, the lingual gyrus is continuous with the parahippocampal gyrus and together they form the medial portion of the fusiform gyrus.