Fornix (neuroanatomy)

The fornix is a C-shaped bundle of nerve fibers in the brain, and is a major output tract of the hippocampus. It carries signals from the hippocampus to the mammillary bodies and septal nuclei. It is part of the limbic system, which is involved in emotion and memory.

The fornix can be divided into several parts:

• Fimbria: The fimbria is the portion of the fornix that originates in the hippocampus. It forms a fringe along the medial edge of the hippocampus.

• Crus: The crus of the fornix is formed as the fimbriae from each hippocampus converge posteriorly.

• Body: The two crura join to form the body of the fornix. The body runs forward beneath the corpus callosum.

• Columns: As the body reaches the anterior commissure, it divides into two columns of the fornix. These columns curve downward and backward to terminate primarily in the mammillary bodies of the hypothalamus, but also send fibers to the anterior thalamic nuclei and the septal nuclei.

The fornix plays a role in spatial memory, declarative memory, and episodic memory. Damage to the fornix can result in memory impairments, particularly affecting the ability to form new memories (anterograde amnesia). Lesions can also affect spatial navigation and recall. The fornix's connections with the mammillary bodies are important for memory consolidation. Its septal connections are implicated in reward and motivation.