how an olfactory stimulus can strengthen memory

Sleep is precious for forging our memory. Scientists have developed a technique to boost it during sleep thanks to the scent of a rose.

The 13 March 2020is world day sleep. Sleeping well is essential for our health but also for our memory. It can be consolidated by what is called "the reactivation targeted memory "or TMR for targeted memory reactivation, in English. This method consists in restimulating a patient in full sleep with the same signals used during an awakened memory exercise. Although the effects of this method on brain oscillations during sleep are unknown, it is recognized that good sleep is essential for building his memory.

Scientists at the Weizmann Institute in Israel have developed a technique based on an olfactory stimulus to reactivate memory during sleep in a single hemisphere. Their work is published in Current Biology.

The scent of a rose that revives memory

On a screen split in two, the words appearing on the right are processed by the left hemisphere and vice versa. Scientists used this principle to develop their TMR experiment. While they memorized which side of the screen the words appeared on, the patients breathed in a scent of rose by the two nostrils. Following the Review, the patients had to put the words back on the right side, then they took a half-hour nap in the laboratory. While sleeping, the rose scent was administered to them again, but through one nostril. After the nap, the patients repeated the Review.

The diffusion unilateral odor has reactivated the memory stored in a single hemisphere. The smell infused by the right nostril reactivated the memories of the right hemisphere, so the patients retained the words better on the left of the screen. Scientists have also observed that a stimulation unilateral changes the slow oscillations and the sleep zones in both hemispheres. These effects were not observed in the control group, which was not exposed to the smell of roses during the memorization phase.

What could this non-invasive method do? Scientists say their experiment could have applications clinical, especially in the case of post-traumatic stress disorder lateralized. Patients who have undergone stroke in one of the two hemispheres could also benefit.

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