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The summer after my freshman year in high school, my family had this potent, pineapple candle that was so strong it never had to be ignited to give off its scent. Whenever we’d clean our dining room or have guests over, my mom would take the lid off the candle and let the tropical smell fill the room. 

Over a year later, I once again found that pineapple candle that we never lit. I took the lid off, and sud­denly was thinking about the Harry Potter books. What does pineapple have to do with Harry Potter? It took me a second to remember what my sub­con­scious already recalled: I read through all the Harry Potter books the summer after my freshman year — the same summer of the pineapple candle.

This reaction hap­pened because nothing reaches con­sciousness unless it has reached the thalamus — the region of the brain that relays motor and sensory signals — , and olfactory input (smell) passes through many other brain regions before getting to the thalamus.

“In neu­ro­science, we say a little bit non­cha­lantly that nothing reaches con­sciousness unless it has passed the thalamus,” Johan Lund­strom, PhD, a faculty member at the Monell Chemical Senses Center in Philadelphia said. “For olfaction, you have all this basic pro­cessing before you have con­scious awareness of the odor.” 

Included in those many brain regions the olfactory input passes before the thalamus are the amygdala and the hip­pocampus, the regions related to emotion and memory.

This means that scents can have a pow­erful influence on storing and recalling mem­ories, some­times without us even knowing it. Often, scents serve as the triggers for our nos­talgia or anxiety.

We do not yet know how odor-asso­ciated mem­ories are stored specif­i­cally, but according to researchers at Boston University’s Center for Systems Neu­ro­science, odor could one day be used as a tool to treat memory-related mood disorders.

“We can poten­tially view memory as its own kind of drug — as an anti­de­pressant or [anxiety reducer],” Boston Uni­versity neu­ro­sci­entist Steve Ramirez said. “And [odor] could be an exper­i­men­tally con­trol­lable factor that we could deliver to people. It may be a very pow­erful tool.”

Taste plays a role in memory too, because what we per­ceive as taste is influ­enced by our olfactory senses, according to Venkatesh Murthy, Harvard Uni­versity chair of the Department of Mol­e­cular and Cel­lular Biology.

Murthy said that when we chew, mol­e­cules in the food “make their way back retro-nasally to your nasal epithelium,” so “all of what you con­sider flavor is smell.”

This is why people say that chewing the same flavor gum while studying for a test and while taking a test improves your memory. It sounds like a bunch of bunk, but it’s actually true because of the anatomical asso­ci­ation between taste, scent, and memory. You could also take advantage of this fact by wearing the same perfume or essential oils, or by drinking the same aro­matic tea, both when you study and take a test on the same matter.

So, as you study for your final exams, con­sider what you’re smelling — it could help you recall answers on test day.