The Science Behind Why We Get Deja Vu: Is there Something Wrong With my Brain?

Have you ever walked into a room or been to a place and felt like you have been there before? But deep down your brain knows that you haven't been there. Sometimes the feeling is uncomfortable and often can leave you wondering if you're losing it. Don't worry though because it is normal; almost everybody gets the feeling of déjà vu. I get it, you get it, your mother gets it. In fact, almost 97% of the world population experiences it at least once in their lifetime. The word déjà vu means "already seen" in French and the term is credited to be named by French philosopher Émile Boriac in 1876. 

Personally, I get déjà vu all the time: in class, at home, or at work. It always feels like I already experienced this moment or visited this space. Déjà vu has always interested me because I couldn't tell whether I was going crazy or I had actually experienced something similar. Sometimes, I trick myself into believing I already know the outcome because I believe that I have experienced the situation before. After researching, I discovered that déjà vu occurs when the wires in your brain get crossed.  The wires in your brain are called axons which are extensions of your brain's neurons that connect with other neurons in your brain in order to send signals to the rest of your body. The part of your brain responsible for déjà vu is the hippocampus in each temporal lobe. Parts of your brain can get incorrectly activated and other regions of your brain have to do a fact check and recall past memories to see if they are connected to this moment. Leaving a strange sense of déjà  Each person has two temporal lobes. The temporal lobes contain a hippocampus which is responsible for storing your short term memory. The temporal lobes are also responsible for your ability to recall words, people, places, language, and your ability to interpret emotions in other people. The hippocampus is responsible for memory recollection and familiarity.

 

                          Location of the Hippocampus                    Location of the Temporal Lobes

The hippocampus contains three major regions: subiculum, hippocampus proper and dentate gyrus. The hippocampus proper is responsible for decision making and memory storage, the dentate gyrus acts as a preprocessor for incoming information, and the subiculum is responsible for memory retrieval. There are two distinct classes of neurons in this area of the brain: projection neurons which send information to more distant parts of the brain and interneurons which send information to nearby neurons. The neurons in control of excitatory synapses tend to be the principal neurons. For clarification, excitatory synapses is when activity from one neuron influences the activity of a nearby neuron triggering a neurological or physical response. 

Hippocampal Anatomy: Source

It is normal for a healthy brain to experience déjà vu at least a few times per year. The feeling is often associated with high levels of exhaustion, being busy, or stressed out. Déjà vu occurrences are more frequent in people who have high level college degrees, travel, or exhibit high levels of intelligence. For the brain, high levels of stress and exhaustion can cause cloudy long term memory. Long term memory storage is associated with the right temporal lobe. 

While experiencing déjà vu occasionally is completely normal, sometimes déjà vu is associated with serious underlying health conditions. More frequent occurrences of déjà vu are associated with people who commonly have seizures. These types of people typically have central nervous system disorders such as epilepsy or narcolepsy. Epilepsy is when clusters of nerve cells in the brain misfire resulting in abnormal bodily response that is presented through a seizure. The most common form of a seizure that people with epilepsy experience is a focal seizure. People who commonly experience focal seizures report to experience intense déjà vu before the seizure occurs.  This occurs because of the  misfiring neurons that form an inccorrect connection between parts of your brain responsible for memory storage, which is in the hippocampus. A focal seizure is when the nerve cells in your brains send out uncontrollable electrical signals. Focal seizures impact motor control (ability to control muscles), sensory feeling (tasting, smelling, seeing, or feeling something that is not really there), sudden intense feelings of happiness, nausea, or anger, repetitive behaviors (blinking, twitching, or involuntarily moving your mouth). The neurotransmitter responsible for excitability is the amino acid glutamate. Glutamate receptors are locatated all throughout the central nervous system which is essential for maintaining optimal glutamate levels in the extracellular space. Glutamate is extremely important to memory, cognition, and mood regulation; too much or too little could have negative affects on your mental health.

  Focal Vs. Generalized Seizure Occurrence. Source

Don't worry, younger people like you and me are more likely to experience spontaneous déjà vu because our brains are more active, more excitable. The temporal lobe in our brains will misfire or get overexcited more frequently than an older persons brain.