A new joint study released by Tel Aviv University (TAU), in partnership with the Weizmann Institute of Science, has discovered a new method for enhancing memory retention and processes in the brain during sleep. The method is dependent on evoking memories via the release of scents in one nostril. Among some the results of the study was additional knowledge on how sleep aids memory, which can later be used to help those suffering memory issues due to brain injuries, or help treat people suffering with post-traumatic stress disorder (PTSD).
The study was led by Ella Bar, a PhD student at TAU and the Weizmann Institute of Science. She was assisted by Prof. Yuval Nir of the Sackler Faculty of Medicine and Sagol School of Neuroscience, as well as Profs. Yadin Dudai, Noam Sobel and Rony Paz, from Weizmann's Department of Neurobiology
"We know that a memory consolidation process takes place in the brain during sleep," Bar explains. "For long-term memory storage, information gradually transitions from the hippocampus – a brain region that serves as a temporary buffer for new memories – to the neocortex. But how this transition happens remains an unsolved mystery," Prof. Nir said in a statement.
"By triggering consolidation processes in only one side of the brain during sleep, we were able to compare the activity between the hemispheres and isolate the specific activity that corresponds to memory reactivation," Prof. Nir noted.
Bar, the lead researcher of the study, remarked on the study's importance, saying that "beyond promoting basic scientific understanding, we hope that in the future this method may also have clinical applications. For instance, post-traumatic patients show higher activity in the right hemisphere when recalling a trauma, possibly related to its emotional content."
"The technique we developed could potentially influence this aspect of the memory during sleep and decrease the emotional stress that accompanies recall of the traumatic memory. Additionally, this method could be further developed to assist in rehabilitation therapy after one-sided brain damage due to stroke," Bar added.
The basis of the study was rooted in the knowledge that memories associated with specific locations on the left side of a given person are typically stored in the right hemisphere of the brain, and vice versa. An experiment conducted tested this proposition, when participants were exposed to the scent of a rose, and asked to remember the location of words presented on either the left or right side of a computer screen. The participants were then tested on the location of the words, then proceeded to nap. While asleep, a portion of those exposed to the rose were re-exposed to the scent in one nostril. It was found that "one-sided" rose scent delivery resulted in different sleep waves in the two brain hemispheres. The brain hemisphere which received the scent revealed better electrical signatures of memory retention during sleep.
"The memory of the subjects was significantly better for words presented on the side affected by smell than the memory for words presented on the other side. Our findings emphasize that the memory consolidation process can be amplified by external cues such as scents," she concludes. "By using the special organization of the olfactory pathways, memories can be manipulated in a local manner on one side of the brain. Our finding demonstrates that memory consolidation likely involves a nocturnal 'dialogue' between the hippocampus and specific regions in the cerebral cortex," Bar concluded.