By: Sophie Gabreldar
Many people associate certain smells with specific memories or events, but why is that?
How Does It Work?
The answer is most likely due to brain anatomy. The olfactory bulb (which starts inside the nose and runs along the bottom of the brain) is responsible for processing incoming smells. The olfactory bulb has deep connections to two brain areas that regulate memory and emotion: the amygdala and hippocampus. Notably, visual, auditory (sound) and tactile (touch) information do not pass through these regions of the brain. This may be why smell is so successful at triggering emotions and memories.
Scientists at Brown University began a study, to see the correlation between the emotional intensity of a memory triggered by a smell and activation in the amygdala. At the start of study, participants first described a positive memory triggered by a particular perfume. Afterwards, participants then came to the lab to participate in an fMRI. A fMRI is a machine that measures brain activity by detecting changes associated with blood flow.
When smelling their chosen perfume, participants showed the greatest activation in the amygdala and parahippocampal gyrus (a region surrounding the hippocampus). This suggests that odors that trigger strong, emotional memories also trigger elevated activity in the brain areas strongly linked to emotion and memory. Nevertheless, it is important to note that there were only five participants in the study. Conducting a much wider study is necessary to confirm these findings.
Another study found evidence that suggests that memories triggered by an odor were accompanied by greater activity in the limbic system (which includes the hippocampus and amygdala). During the study, the scientists would discover that memories sparked by odors were linked to more brain activity in areas associated with visual vividness.
Are There Any Negative Effects?
In some cases, it can trigger negative emotions, particularly in individuals with post traumatic stress disorder (PTSD). A study done by conducting three clinical case studies of individuals diagnosed with PTSD who experience this phenomenon. During the study one patient frequently experienced disturbing memories, feelings of guilt, and nausea when smelling diesel.
The participants even began to actively avoid situations in which he might smell diesel (like driving behind trucks). The smell of diesel brought him back to an accident in Vietnam that he initially experienced over 30 years ago.
Don’t underestimate the power of your sense of smell!