Hippocampus. Have you ever gone blank and forgotten what you were going to say? Our brain is full of important data and information that we have stored over the years. Sometimes we have so much information that we force our brain to get rid and ignore some data. The part of the brain in charge of such important functions as memory and learning is the hippocampus. Without this brain structure, we would lose the ability to remember and feel the emotions associated with memories. You want to know more? Keep reading!
What is the Hippocampus?
The hippocampus is named after the anatomist Giulio Cesare Aranzio who in the 16th century observed that this brain structure bears a great resemblance to a seahorse.
The word hippocampus comes from the Greek Hippos (horse) and Kampe (crooked). In his discovery, this part of the brain was related to the sense of smell and he advocated the explanation that the hippocampus’ main function was to process the olfactory stimuli.
This explanation was defended until in 1890 when Vladimir Béjterev demonstrated the actual function of the hippocampus in relation to memory and cognitive processes. It is one of the most important parts of the human brain because it is closely related to memory functioning and emotions. It is a small organ located within the temporal lobe (approximately behind each temple), which communicates with different areas of the cerebral cortex in what is known as the “hippocampus system.” It is a small organ with an elongated and curved shape. Inside our brain, we have two hippocampi, one in each hemisphere (left and right).
The hippocampus is known as the main structure in memory processing.
Where is the Hippocampus?
It is very well located, connected to different regions of the brain. It is located in the middle temporal lobe.
The hippocampus along with other brain structures such as the amygdala and hypothalamus form the limbic system and are responsible for managing the most primitive physiological responses. They belong to the most “ancient, deep and primitive” part of the brain, in a part of the brain known as “archicortex” (the oldest region of the human brain) that appeared millions of years ago in our ancestors to meet their most basic needs.
What does the Hippocampus do?
Among its main functions are the mental processes related to memory consolidation and the learning process. As well as, processes associated with the regulation and production of emotional states and spatial perception. How does the brain learn?
Some research has also linked it to behavioral inhibition, but this information is still in the research phase as it is fairly recent.
Hippocampus and Memory
The hippocampus is primarily related to emotional memory and declarative memory. It allows us to identify faces, to describe different things and to associate the positive or negative feelings that we feel with the memories of the lived events.
It intervenes in forming both episodic and autobiographical memories from the experiences we are living. The brain needs to “make room” to be able to store all the information over the years and for this, it transfers the temporal memories to other areas of the brain where memory storage takes place in the long term.
In this way, older memories take longer to disappear. If the hippocampus were damaged, we would lose the ability to learn and the ability to retain information in memory. In addition to allowing the information to pass into long-term memory, it links the contents of the memory with positive or negative emotions that correspond depending on whether the memories are associated with good or bad experiences.
There are many types of memory: semantic memory, visual memory, working memory, implicit memory, etc. In the case of the hippocampus, it intervenes specifically in declarative memory (it covers our personal experiences and the knowledge we have about the world), managing the contents that can be expressed verbally. The different types of memory are not governed solely by the hippocampus but are formed by other brain regions. It does not take care of all the processes related to memory loss but it covers a good part of them.
Hippocampus and Learning
It allows learning and retention of information since it is one of the few areas of the brain that have neurogenesis throughout life.
That is, it has the ability to generate new neurons and new connections between neurons throughout the life cycle. Learning is acquired gradually after many efforts and this is directly related to it. For new information to be consolidated in our brains, it is vitally important that new connections are formed between neurons. That is why the hippocampus has a fundamental role in learning.
Curiosity: Is it true that the hippocampus of London taxi drivers is bigger or more developed? Why? London taxi drivers must pass a hard memory test where they must memorize a myriad of streets and places to get the license. In the year 2000, Maguire studied London taxi drivers and observed that the posterior hippocampus was greater. He also noted that the size was directly proportional to the time the taxi drivers were working. This is because of the effect of training, learning and experience changes and shapes the brain.
Spatial perception and its relationship with the hippocampus
Another important function in which the hippocampus stands out is the spatial orientation, where it plays a very important role.
Spatial perception helps us to keep our mind and body in a three-dimensional space. It allows us to move and helps us interact with the world around us.
There have been different studies with mice where it is stated that it is an area of vital importance for orientation capacity and spatial memory.
Thanks to its correct functioning, we are capable of performing acts such as guiding us through cities we do not know, etc. However, the data concerning people are much more limited and more research is needed.
What happens when the hippocampus is disturbed?
An injury to the hippocampus can mean problems generating new memories. An brain injury can cause anterograde amnesia, affecting specific memories but leaving intact learning skills or abilities.
Lesions can cause anterograde or retrograde amnesia. Non-declarative memory would remain intact and uninjured. For example, a person with a hippocampal injury may learn to ride a bicycle after the injury, but he would not remember ever seeing a bicycle. That is, a person with the damaged hippocampus can continue to learn skills but not remember the process.
Anterograde amnesia is memory loss that affects events occurring after the injury. Retrograde amnesia, on the other hand, affects the forgetfulness generated before the injury.
At this point, you will wonder why the hippocampus is damaged when there are cases of amnesia. It is simple, this part of the brain acts as a gateway to brain patterns that sporadically retain events until they pass to the frontal lobe. One could say that the hippocampus is key to memory consolidation, transforming short-term memory into long-term memory. If this access door is damaged and you can’t save the information, it won’t be possible to produce longer-term memories. In addition to losing the ability to remember, when injuries or damage to the hippocampus occurs, you may lose the ability to feel the emotions associated with such memories, since you would not be able to relate the memories to the emotions that evoke it.
Why can the Hippocampus be damaged?
Most of the alterations that may occur in the hippocampus are produced as a result of aging and neurodegenerative diseases, stress, stroke, epilepsy, aneurysms, encephalitis, schizophrenia.
Aging and dementias
In aging in general and dementias such as Alzheimer’s disease in particular, the hippocampus is one of the areas that has previously been damaged, impairing the ability to form new memories or the ability to recall more or less recent autobiographical information. Memory problems, in this case, are associated with the death of hippocampal neurons.
Most of us know of someone who has suffered or suffers from some kind of dementia and has experienced memory loss. It is curious how the memories that remain are childhood memories or the oldest memories. You may wonder why this happens if the hippocampus is supposed to be damaged.
Well, although it is severely damaged (whether by dementia or any other type of illness), the most common memories are the oldest and they are also the most relevant to the life of the person. This is because over time these memories have been “becoming independent” of the hippocampus to be part of other structures related to long-term memory.
Hippocampus and stress
This region of the brain is very vulnerable to periods of stress because it inhibits and atrophies the neurons of this structure.
Have you noticed that when we are very stressed and we have a billion things to do sometimes we feel forgetful?
Stress and specifically cortisol (a type of hormone that is released in response to stressful moments) damage our brain structures sometimes causing neuronal death. That is why it is fundamental that we learn to remain calm and manage our emotions to get our hippocampus to remain strong and continue to exercise their functions optimally.
To know more watch the following video.
If you like this super interesting subject about memory, I recommend you watch the movie “Memento”. I’ll leave the trailer here so you can see what it’s about.
If you liked this post, leave your comment below. I will be happy to read it and answer your questions :).
This article is originally in Spanish written by Mairena Vázquez, translated by Alejandra Salazar.