What Is the Hippocampus?

The hippocampus plays a critical role in the formation, organization, and storage of new memories and in connecting certain sensations and emotions to these memories. It also plays an important part in the recall of emotional memories. Have you ever noticed how a particular scent might trigger a strong memory? It is the hippocampus that plays a role in this connection.

Functions of the Hippocampus

Research has also found that different subregions of the hippocampus play important roles in certain types of memory.

Spatial Memory

The rear part of the hippocampus is involved in the processing of spatial memories. Studies of London cab drivers found that navigating complex mazes of big city streets is linked to the growth of the rear region of the hippocampus.

Memory Consolidation

The hippocampus also plays a role in consolidating memories during sleep. Studies published in 2004 suggest that greater hippocampal activity during sleep following some sort of training or learning experience leads to better memory of the material the following day.

Memory Transfer

Memories are not stored in the hippocampus for the long term. Instead, it is believed that the hippocampus acts as something of a shipping center, taking in information, registering it, and temporarily storing it before shipping it off to be filed and stored in long-term memory. Sleep is believed to play a critical role in this process.

Risk Factors

There are a few different factors that can affect the function of the hippocampus:

• Age: Age can also have a major impact on the functioning of the hippocampus. MRI scans of human brains have found that the human hippocampus shrinks by around 13% between the ages of 30 and 80. Those who experience such a loss may show significant declines in memory performance. Cell degeneration in the hippocampus has also been linked to the onset of Alzheimer’s disease.
• Stress: Stress can take a toll on the hippocampus, and may impair memory abilities. 
• Social isolation: Loneliness and social isolation can have a variety of negative health effects, and research shows that they can also affect the functioning of the hippocampus.
• Lack of exercise: Lack of physical exercise may have detrimental effects on the brain, but research has found that exercise may help enhance hippocampal health and combat age-related cognitive decline.
• Depression: Research has shown that people with recurring, poorly treated depression experience decreased hippocampal size.
  
  

The hippocampus may also play a role in contributing to the development of addictions. Because drugs and alcohol affect the brain's reward systems, the hippocampus creates memories of these satisfying experiences. It also may help form memories of environmental cues associated with substance use that can contribute to intense cravings when these cues are encountered again.

Effects of Hippocampus Damage

There are a number of things that can cause hippocampus damage, including traumatic brain injury, stroke, Alzheimer's disease, seizures, and ischemia.

If the hippocampus is damaged by disease or injury, it can influence a person's memories as well as their ability to form new memories. Hippocampus damage can particularly affect spatial memory, or the ability to remember directions, locations, and orientations.

Damage to the hippocampus has been observed upon post-mortem analysis of the brains of individuals with amnesia. Such damage is linked to problems with forming explicit memories such as names, dates, and events.

The exact impact of damage can vary depending on which hippocampus has been affected. Research on mice suggests that damage to the left hippocampus affects the recall of verbal information, while damage to the right hippocampus results in problems with visual information.

Signs of Hippocampus Damage

Some of the signs of damage or injury to the hippocampus include:

• Changes in cognitive functioning
• Mood dysfunction
• Problems storing memories
• Difficulty recalling long-term memories
• Spatial disorientation and getting lost in familiar places
• Losing or misplacing items often
• Problems following directions
• Problems with decision-making
• Difficulty carrying on conversations

In addition to memory problems and other symptoms often linked to Alzheimer's disease, problems with the hippocampus are also linked to mental health conditions such as bipolar disorder, depression, and schizophrenia.

How to Keep Your Hippocampus Healthy

So what can you do to protect your hippocampus? Some tips that may help protect the health of your hippocampus include:

• Exercise regularly: Research suggests that exercise may help protect the hippocampus from the detrimental effects of aging. 
• Manage your stress: Long-term stress can also have a negative impact on the hippocampus, so finding ways to manage your stress may help protect this part of your brain.
• Treat mental health conditions: Conditions such as PTSD and depression are associated with changes to the hippocampus. For example, some research suggests that stress associated with PTSD may also lead to damage to the hippocampus. People with PTSD have smaller hippocampi than people without PTSD.
• Protect your brain: Head trauma can damage the hippocampus, so it is important to utilize protective equipment, including helmets and seatbelts, in situations where an accident might result in a brain injury.

History of the Hippocampus

The term hippocampus is derived from the Greek word hippokampus (hippo meaning "horse" and kampos meaning "sea monster") because the structure resembles the shape of a sea horse. The structure was first described by the anatomist Julius Caesar Aranzi. Because the hippocampus has been known of and observed for centuries, it is one of the most studied areas of the brain.