Smell Found Linked to Emotion
New Finding May Help Treat Depressed People
New studies being conducted all over the world are coming close to proving that those with post traumatic stress or depression associate smells with negative memories.
Researchers at Northwestern University have been conducting studies on the sense of smell to determine how it relates to mental disorders and basic human instinct. Their research has recently been reported in the journal Science and has backed up evidence that smell and emotion are linked in keeping us out of harm's way and even further explaining disorders such as post-traumatic stress syndrome.
The researchers at Northwestern came to these findings by giving 12 healthy young adult volunteers electric shocks while they sniffed different odors. These odors were significantly different from ones that the average person would smell in everyday life. These smells were a mix of laboratory chemicals. Two of the bottles contained the same substance. The third was a mirror image that was indistinguishable. The volunteers correctly guessed the odd odor one-third of the time. Then they were given small electric shocks while they smelled the odd chemical and could then select the odd odor 70 percent of the time. MRI scans confirmed that the improvement in their guessing was attributed to how the volunteers’ olfactory senses changed its storage of the odor information once the negative shocks were administered.
Smell and Memory
It is well established that different scents can trigger old memories, both positive and negative. These memories are especially significant and personal to individuals. It is what helps humans pick out dangerous scents and respond to them, such as smoke from a fire. However, the brain is unable to distinguish between similar odors that might not be as dangerous, such as smoke from a fire contained in a fireplace versus a house fire. This could be what causes anxiety disorders to develop, causing a person’s fight-or-flight response to overreact. However, more research is needed before this theory can be confirmed.
If confirmed, the disorders that are affected by the sense of smell, such as post traumatic stress disorder and depression, can be better understood. Previous studies have been undertaken to measure brain responses to the other senses, including sight and hearing, with images and words, and they have found that people respond to these images differently than smell.
A Similar Study
A similar but different study was conducted by Dr. Bettina Pause at Christian-Albrechts-University of Kiel in Germany. They studied 25 depressed volunteers versus 25 healthy volunteers on how sense of smell responded to emotional stimuli compared to the sense of sight. Afterwards, 15 of the depressed patients who had been treated for their condition were re-examined after their recovery to see if their responses had changed.
The participants watched a slide show of neutral colors while inhaling various smells ranging from that of roses to rotten butter. Their response to these stimuli was measured by electrodes placed on their heads to track their brain activity. They found that the depressed patients were less responsive to the smells and visuals than the healthy participants, though the information was processed differently. Those patients who were treated and retested showed the same response as the healthy patients.
Where the Relationship Stems
The differences in processing the sense of smell in depressed patients has been pinpointed to the main olfactory bulb, located below the orbit frontal cortex in the brain. This pea-sized piece of the brain is said to be responsible for the olfactory triggers that depressed people face. If confirmed, it will make the sense of smell one of the most important senses in the human body.
