The Special Skills of the Sense of Smell

 The Special Skills of the Sense of Smell

As one of the most complex senses in the human system, olfaction continues to provide insight into the process of memories. When researchers learn more about the sense of smell’s role in encoding and recalling memories, there are more questions regarding further implications of findings. Research done by Grella et. al. in 2020 elaborated on the systems consolidation theory for episodic fear memories, finding that fear memories are first processed in the hippocampus then become more reliant on the prefrontal cortex as time passes, but more importantly for olfaction, they found that odor influences memory in that it favors the hippocampus even at remote time points.

The systems consolidation theory proposes that recent memories are stored in the hippocampus, but as time passes, they become more reliant on the prefrontal cortex and less on the hippocampus. The findings of the experiment show that when smell is involved in the encoding of memories, the recall of them can be as vivid as when they were first remembered since they continue to favor the hippocampus as a storage point. The experiment done on 51 male mice showed that mice who were exposed to an almond extract odor at the time of a fear inducing shock were more likely to remember the aversive stimulus 21 days after they were first conditioned as opposed to the subjects that were not exposed to the almond odor (Grella et al., 2020). This finding gives an understanding to the vividness of memories elicited in patients with post traumatic stress disorder (PTSD) even years after initial exposure to trauma as odor plays a significant role in triggering these memories. 

Prior to Grella’s research in 2020, an article was written by Ian Chant and Victoria Stern for Scientific American, titled “Smell Tests Could One Day Reveal Head Trauma and Neurodegenerative Diseases”. This article cites research done at the Department of Defense which showed that a diminished sense of smell predicted frontal lobe damage in 231 soldiers that had suffered injuries related to head traumas and blasts (Chant & Stern, 2016). The authors assert that due to the different location memories can be stored in, the ability to describe and verbally name an odor can require a decent amount of cognitive coordination, and a damaged sense of smell can be indicative that the connections that support this coordination could be affected by disease or brain injury. Sniff tests that require the identification of a smell could be helpful in diagnosing brain injuries, and because of this researchers have been working on creating an olfaction test to efficiently track damage in the brain. 

The findings of Grella’s research and potential for smell tests could help in the realm of memory recall and brain damage. If an individual were to have suffered a brain injury but also have PTSD, what implications would this have on the ability to recall memories, or how would these factors affect treatment? Furthering understanding of the relationship between memories, smell, and brain damage can help to discover interventions and treatments to help those dealing with these multiple complications.  

References: 

Chant, I. & Stern, V. (2016). Smell Tests Could One Day Reveal Head Trauma and 

Neurodegenerative Disease. Scientific American. 

https://www.scientificamerican.com/article/smell-tests-could-one-day-reveal-head-trauma

-and-neurodegenerative-disease/ 

Grella, S. L., Fortin, A. H., McKissick, O., Leblanc, H., & Ramirez (2020). Odor modulates the 

temporal dynamics of fear memory consolidation. CSH Press Learning & Memory, 27, 150-163. http://www.learnmem.org/cgi/doi/10.1101/lm.050690.119.