Every day, one cannot help but notice the distinct smells of different places at Concord Academy: the scent of whiteboard markers permeating the Language Hall, the inviting aroma of coffee in the faculty lounge, and the smell of freshly mown grass on the Quad. As one makes their way around campus, the familiar aromas of various places evoke a flood of memories. For instance, the smell of freshly baked cookies in a common room may recall the beginning of boarding life. These “odor memories” are particularly evocative due to the olfactory sense’s connection with areas of the brain involved in memory processing.
The human nose contains olfactory receptors, which bind to scent molecules upon entering the nose. Once this happens, olfactory sensory neurons transfer electric signals to different areas of the brain. The signals pass through the olfactory bulb before reaching other brain regions. The olfactory bulb, located in the forebrain, is the initial processing center for olfactory information and directly connects to the amygdala, which processes emotions, and the hippocampus, which is linked to cognition and memory. If the smell is connected to a particular emotional moment, the information gets stored as a long-term memory.
Unlike the olfactory sense, sights, sounds and other senses reach the thalamus, the brain’s relay station, before entering the amygdala and hippocampus. Therefore, due to the greater physical distance between these brain regions, memories aroused by sight and sounds are less emotional and vivid than those triggered by odors.
Harnessing the power of scent to trigger memories, scientists have even tested the possibility of using scent to diagnose and treat dementia patients experiencing memory loss. Dementia is a collection of symptoms caused by diseases such as Alzheimer’s, frontotemporal dementia, and Lewy body dementia. The main symptom of dementia is the loss of cognitive abilities. Research suggests that the olfactory bulb is one of the first brain regions affected by dementia. A 2024 study conducted by researchers Yukifusa Igeta, Isao Hemmi, Kohei Yuyama, and Yasuyoshi Ouchi found that odor identification scores successfully detected the amyloidogenesis stage of Alzheimer's disease. A version of the test consisting of only four scents—India ink, wood, curry, and sweaty socks, proved most effective.
Although still a new and untested form of complementary and alternative medicine (CAM), scent therapy combined with reminiscence therapy is already employed in a lot of hospitals and care facilities. Reminiscence therapy, a widespread form of CAM, helps patients with dementia recall memories from their past. A retirement home in New York City even offered residents rotating smells that evoke a sense of nostalgia, such as the scents of baseball mitts and hot dogs.
The connection between the olfactory bulb and the hippocampus reflects the process of memory, and serves as a valuable model for understanding it.