The cingulum is an anatomical term used for a bundle of white-matter fibers found in the brain. In plural form, it is cingula. Although the term is best known for its association with the brain, it is used for other parts of the body as well. Cingulum is of Latin origin, meaning "belt" or "girdle." In Ancient Rome, soldiers wore military belts called cingulum militare, which were designed to hold their sword and dagger.
The brain matter is similar to its ancient namesake in that it forms an encircling or ring-like structure around the brain. Specifically, it expands from the cingulate gyrus to the entorhinal cortex. These regions form part of the cerebral cortex, the top-positioned part of the brain instrumental in human functions such as attention, speech, consciousness and memory.
Forming the inner border of the cerebral cortex and buried within the brain's cerebrum is the limbic system. Containing brain structures such as the amygdala, anterior thalamic nuclei, fornix and limbic cortex, the limbic system, according to researchers in the medical field, is specifically responsible for human functions such as long-term memory, emotion and the sense of smell. The cingulum forms part of this particular system as a conduit of communication in the brain. It is able to accomplish this with its axons, which are long projections of nerve cells that generate electrical impulses away from the cells' body.
The cingulum derives its white color from its myelin. This is the fatty substance that surrounds the structure's axons. Acting as an electrical insulation device, the myelin is therefore instrumental in speeding up the rate of communication in the brain. In this sense, the white-matter bundle acts as a network cable.
Coincidentally, the cingulum is situated on top of the corpus callosum, which is also part of the limbic system and is responsible for communication transfer. The corpus callosum, however, is larger than the cingulum. In fact, it is the largest bundle of white matter in the brain, with an axon count of up to 250 million.
The term cingulum has other meanings. In dentistry, it is used for a bulge at the anterior tooth, such as the incisor or canine. The term also applies to the pelvic girdle and shoulder girdle, known as cingulum membri pelvini and cingulum membri thoracici, respectively.