Smell-sensing neurons in the nose extend directly to the olfactory bulb of the brain, from which they can be passed on to other brain regions — including areas involved in memory. The sense of smell is specific, which helps to explain how our smell memories can be so precise.
Decades later, researchers hypothesized that the exceptional ability that smells have to trigger memories — known as “the Proust effect” — is due to how close the olfactory processing system is to the memory hub in the brain.
Although we often look at pictures to remember the past, odors are actually better at helping us remember. Brain scans show that odors bring on strong memories because of the brain regions that process them. The group of brain areas that are best known for processing emotions, learning, and memory also process odors.
Smells are handled by the olfactory bulb, the structure in the front of the brain that sends information to the other areas of the body's central command for further processing. Odors take a direct route to the limbic system, including the amygdala and the hippocampus, the regions related to emotion and memory.
The Olfactory System and the Brain
When those are important or salient events, the odor can be strongly associated with the memory—to the extent that re-experiencing the odor often revives the emotions or feelings that were initially experienced, Dalton explains.
Scents bypass the thalamus and go straight to the brain's smell center, known as the olfactory bulb. The olfactory bulb is directly connected to the amygdala and hippocampus, which might explain why the smell of something can so immediately trigger a detailed memory or even intense emotion.
Odors are claimed to be more closely connected to affect than other sensory experiences. They can serve as potent contextual cues for memory formation and emotional conditioning and can also serve as cues for olfactory flashbacks.
A recent study done by German neuroscientists, Christina Strauch and Denise Manahan-Vaughan, has proven that our brain relates odors and the feeling of nostalgia by categorizing scents in the same area that stores long-term memories — the amygdala.
Triggers can be people, places, or situations. Thoughts, emotions and sensations can also trigger trauma memories. Triggers can be something specific tied to the memory of the traumatic event (like bridges, the smell of fuel or feeling afraid) or something general (like being in a crowd).
Flashbacks can be triggered by a sensory feeling, an emotional memory, a reminder of the event, or even an unrelated stressful experience. Identify the experiences that trigger your flashbacks. If possible, make a plan on how to avoid these triggers or how to cope if you encounter the trigger.
There are two key reasons why this occurs. The first reason is simply that something smells like them. The second reason is that your mind tricks you into thinking you smell them, usually triggered when you think about the person. How do pheromones work?
Because the olfactory bulb and cortex are so close physically to the hippocampus and amygdala (huge factors in memory retention), smell is considered the strongest and quickest memory inducer.
According to McLaughlin, if the brain registers an overwhelming trauma, then it can essentially block that memory in a process called dissociation—or detachment from reality. "The brain will attempt to protect itself," she added.
Experts have different opinions on whether forgotten memories can be recalled, but some researchers believe those memories haven't completely disappeared from your brain. Specific triggers later in life may help jog your memory, unlocking the traces that remain.
Roses, lavender, jasmine and leather can remind us of many other childhood memories. The smells of Christmas are special smells with their childhood connections to religious themes and holiday themes (of getting what you need and what you want.)
The top 10 smells which trigger nostalgic memories of school days, holidays and loved ones include sun cream, bubble gum, fish and chips, freshly mown grass, candy floss (cotton candy for those in the US) and rain on hot tarmac.
What do brains smell like? As a neurosurgeon, and doing brain surgery on a weekly basis, I can tell you brains have no smell. Any Mal odor coming from the patient during a craniotomy is believed to be an infection from one of the structures surrounding the brain or the brain itself.
Many individuals with PTSD, however, report that trauma-related odors are particularly potent reminders of past traumatic events (e.g. odors associated with explosions or “burning” materials).
Clinical Body Memory (CBM) Mechanisms
Bodily experiences include the feeling of touch, pain or inner signals of the body (i.e., interoceptive signals) often in combination with emotional experiences such as stress, discomfort or fear.
Phantosmia may be caused by a head injury or upper respiratory infection. It can also be caused by aging, trauma, temporal lobe seizures, inflamed sinuses, brain tumors, certain medications and Parkinson's disease. Phantosmia can also result from COVID-19 infection.
We often take our sense of smell for granted. But scent is an incredibly powerful trigger for memory recall, as the human olfactory system is linked directly to the most primitive parts of our brain.
Researchers at Utrecht University in the Netherlands found that it's possible for people to "smell" emotions like fear or disgust through excreted chemical signals.
For anyone who's ever forgotten something or someone they wish they could remember, a bit of solace: Though the memory is hidden from your conscious mind, it might not be gone. In a study of college students, brain imaging detected patterns of activation that corresponded to memories the students thought they'd lost.
The good news is that it's completely normal not to remember much of your early years. It's known as infantile amnesia. This means that even though kids' brains are like little sponges, soaking in all that info and experience, you might take relatively few memories of it into adulthood.
Memory erasure has been shown to be possible in some experimental conditions; some of the techniques currently being investigated are: drug-induced amnesia, selective memory suppression, destruction of neurons, interruption of memory, reconsolidation, and the disruption of specific molecular mechanisms.