The Hippocampus and Depression
The brain is a fantastic organ!
It allows us to create meaning by combining sensory and cognitive data. This integration occurs through associations, otherwise known as memories.
Memories contextualize our reality and are stored throughout our vast cortex.
Not only can the brain store incredible amounts of information (See Love Bytes ); it has techniques to retrieve them very quickly.
That makes sense because it has been anthropologically important for early Homo sapiens to recognize threat from safety.
Any given thought or memory, requires many areas of the cortex to light up simultaneously.
These twinkling stars inside the skull’s night sky correspond to both external sensory signals and inner feelings, like hunger or arousal, associated with the original experience.
There are close to an infinite amount of memories and thoughts at your disposal, like there are an infinite amount of songs within any piano.
The drama of the song, or intensity of the memory, is related to how many distinct brain areas are activated and in what order. This would be similar to the notion that the sentence you are currently reading creates its meaning from each word chosen, in this specific sequence.
Actually, the piano is a good metaphor for the brain if you consider that any one memory, or mental note, is the result of playing a specific combination of neurons throughout the brain.
Some pieces of life are more dramatic, striking chords that activate many brain centers simultaneously.
This understanding helps explain the notion of ‘Why humans only use 10% of their brain at any given time’.
The rest is not lazy tapioca.
The ‘unused’ portion of the cortex represents a potential inventory of almost infinite thoughts. If we used ALL of our brain at once, the mind would experience the equivalent of playing all of the notes on the keyboard at once: noise without meaning.
If thoughts were colors, the mind would be blinded by the light and see nothing else.
So the brain is the entire orchestra, creating the music of your reality by choosing thoughts and arrangements, as situations demand.
And to help us along, there is a memory maestro in the mind’s midst.
If members of the orchestra were parts of the cortex, it is this memory maestro that coordinates when some neurons play, or don’t. It also keeps the diverse functional sections working together in harmony.
In the brain, your HIPPOCAMPUS conducts the various instruments of your memory.
This graceful looking structure, with a seahorse body, is buried deep beneath the entire ocean of the cerebral cortex. These bilateral stallions gallop when thoughts race. Its long graceful dendritic limbs comb your cranial concert hall, sifting through songs silently singing in cells.
The Hippocampus is the conductor of our memories- selecting which neurons are played together.
By using associations, every familiar image we encounter is instantly reunited with former band members. It seems that the Hippo’s main job is one of ‘PATTERN COMPLETION’, as it organizes Episodic Memories.
This is the phenomenon we experience when the smell of cinnamon reminds us of Valentine’s Day (hope you have a happy one!)
Studies demonstrate that if we experience 2 things together, they become associated as a memory. Later, if we are shown only 1 of those things, the hippocampus automatically retrieves both things.
The hippocampus does this to remind us of prior experiences. It attempts to provide us with context to interpret reality, and tries to predict the most powerful relationship between a concepts or objects. This then enriches our perception of the real-time performance of life.
As an exercise to illustrate this phenomenon, consider the following:
If I ask you to think about Balloons, there may be too many associations to come up with 1 specific memory experience.
If I ask you to think of a number, like 99, many will think of Mr. Gretzky, Maxwell Smart, or Jay-Z (who recently had 99 problems).
But if I ask you to think about 99 Red Balloons, I have a feeling, there will be music playing in your head.
In 2004, Dr. Glenda McQueen, a Psychiatrist from Calgary, Canada, examined the relationship between the hippocampus and depression.
She examined post mortem studies of depressed people, animal models of stress, and compared levels of depression with the size of the Hippocampus in humans.
Clinical Major Depressive Disorder is often characterized by episodes of poor concentration, sad mood and inability to enjoy oneself, among other symptoms. When clinically depressed, much of life can feel overwhelming: hunger and sleep can feel like strangers, suicide can seem like a solution.
This perception of stress during major depressive disorder causes the brain to produce CORTISOL.
Cortisol is like a Lightsaber in your brain.
It is sometimes very helpful, to use the force of this chemical to keep the body going in stressful situations. When levels of cortisol stay high for weeks to months, the biochemical heat of this survival weapon becomes self destructive to cells of the brain.
It has been demonstrated, in clinical depression that elevated levels of cortisol can preferentially damage the HIPPOCAMPUS itself.
MRI data indicates that prolonged episodes, or multiple severe episodes, can result in brain damage, where the HIPPOCAMPUS ACTUALLY SHRINKS IN SIZE.
Can you imagine how an orchestra would react if the conductor forgot the song?
Like anyone who feels a bit lost, the hippocampus tries to fake its way through depression, even though it is disintegrating.
When this happens, the playlist becomes redundant: sad songs, with dull notes.
The concert of life disintegrates and the depressed person grows tired of our societal sing-along: avoiding parties, relationships, and the chorus of other supports they once harmonized with.
This may help to explain why depressed people describe ‘forcing themselves to smile’, or ‘sucking it up’, as almost impossible.
The Hippocampus cannot find the Joy Division.
On a brighter note, Dr. McQeen’s research also indicated that with successful treatment of depression (antidepressant medications or talk therapy), the hippo can be healed. Successful treatment often lowers perceived stress and boiling cortisol levels have a chance to cool.
In the brain’s healing process, treatment also increases another very helpful chemical called BRAIN DERIVED NEUROTROPHIC FACTOR (BDNF). BDNF acts like CHIA-PET™ seeds, in your brain.
With less cortisol, and more BDNF, the hippocampus can repair itself.
The salvation of this Seahorse has been demonstrated to parallel an improvement in the clinical symptoms of Depression.
Perhaps in the future, Depression will receive a different billing. Although ‘Cortisol-Induced Hippocampal Damage Syndrome’ doesn’t exactly roll off the tongue.
Simon Trepel, MD
Simon Trepel, MD FRCPC, is a practicing Child and Adolescent Psychiatrist, in Winnipeg, Canada. He is an Assistant Professor, at the University Of Manitoba, in the Faculty of Medicine, and the Co-founder of the GDAAY Clinic. He is, more importantly, the proud Father of 2 beautiful Daughters. He writes in his spare time about things he knows something about, and occasionally about things he doesn’t; like Yoga, and Italian flavored coffees. He was not referring to coffee that tastes like an Italian person.
Check out his Blog, called Simon Says Psych Stuff, at
