The hippocampus is the part of the brain anatomy located beneath the cortex within the inner folds of the medial temporal lobes. It controls memory and the capability for spatial navigation. It is an extension of the cerebral cortex and one of the structures within the brain that makes up the limbic system, which is responsible for emotions, memories, motivation and other “preconscious” functions.
Curled like a ram’s horn beneath the medial temporal lobes, the hippocampus runs like a thick rope from one side of the brain to another. The two interlocking parts that make up this part of the brain are called the Ammon’s horn and dentate gurus. The hippocampus’ appearance has been compared to a seahorse. The Latin term for the creature gives the hippocampus its name.
Historically, hippocampus function was thought to be responsible for the sense of smell, but that theory has since been disproven. It is now known to control the memory of smell, and not the sense of smell itself. Hippocampus function also was once believed to include the ability to experience inhibition, but that theory seems to have fallen out of favor as well.
Scientists now generally divide hippocampus function into two primary areas: memory and spatial orientation. The hippocampus allows for new episodic memories — memories about experiences or events — to be recorded and stored for retrieval at a later time. It is the part of the brain’s anatomy that helps an individual find his way around without conscious thought. The hippocampus figures into the process of finding short cuts and new routes between locations. Taxi drivers have been found to have larger-than-average hippocampi.
When the hippocampus is damaged, individuals might find it difficult to recall recent events, or they might easily lose their way. Hippocampus function can be affected by illness or injury. For example, this is one of the first parts of the brain affected in Alzheimer’s disease. This is why the early stages of that condition are characterized by a tendency to become disoriented and a loss of short-term memory, even as long-term memory remains. In addition to Alzheimer’s disease, the hippocampus can be damaged by oxygen starvation, encephalitis, and medial temporal lobe seizures.
Seizures that affect the medial temporal lobe tend to bring about profound sensations of déjà vu, amnesia, and feelings of unfamiliarity and fear. These seizures can cause individuals to have “out of body” feelings and experience smells, tastes, or sounds that actually are not present. The hippocampus is believed to be involved in severe mental illness, including schizophrenia and certain types of depression.