Wednesday, February 28, 2018

TMRs Contribution to Memory Consolidation in Sleep Learning


“Did you ever feel, as though you had something inside you that was only waiting for you to give it a chance to come out? Some sort of extra power that you aren’t using- you know, like all the water that goes down the falls instead of the turbines?”
-Aldous Huxley, Brave New World
Our brain is made up of over 100 billion neurons, providing the transportation for all the information we perceive and process. The superiority, vastness, and exceptionality of the human brain has far surpassed those of our primate ancestors. With so much thought, emotion, and free-will there is much to be discovered. There must be more to our brain than what we use in our daily routines. We are constantly seeking to understand, learn, and improve the way we communicate with not only each other but our environment.  Time and money seem to play a key role in the opportunities we as learners use to dictate our perception of possibilities.
Enter: Sleep Learning. We have seen the sci-fi movies, and read the books (Brave New World) and it sounds to me like such an endearing endeavor to drift away and make educational use of the eight hours* I spend in bed every night; perhaps learning a new language, making sense of my MCAT booklets, etc. Prior to this seminar, I had listened to a podcast by Tony Robbins pertaining to sleep learning. He described his sleep tapes that contained rehearsed affirmations of his character and ability and he truly believed these tapes helped him to get through some hardships he encountered. It is interesting to me the clinical indications of studies performed recently show the possibility for astounding things to be learned while asleep, but simply put, we are just not there yet.
Ken Paller, director of the Cognitive Neuroscience Program at Northwestern University, discussed his lab and the use of targeted memory reactivation (TMR) to improve spatial learning. There were three general steps to the project: learning alongside the use of an auditory component, subjects were measured via encephalography while the sound was cued during their slow wave sleep, and the final step was a memory test shortly after wake. The findings indicated a strong increase in accuracy when the auditory component was presented vs the control. This tells us that TMR may contribute to memory consolidation and reactivation. Further studies built upon this project may become applicable to memory improvement in age-related memory decline, sleep disorders, and improving skill learning.
Similarly, an article published by Susan J. Sara titled “Sleep to Remember” presents a dual hypothesis similar to Paller’s findings. This hypothesis describes the relative contributions of both slow-wave sleep and rapid eye movement states to memory consolidation. What I found most interesting was the mention in both articles of spindle oscillations. These spindles indicate a burst of neural activity from thalamic regions in the brain. The spindles have been studied and proven to contribute to memory consolidation and sensory processing in mammals. Furthermore, the article cited the following:
“It has recently been discovered that mild acoustic stimulation is effective in increasing the magnitude of slow waves during sleep and that this enhancement leads to the same memory enhancement as the transcranial DC stimulation (Bellesi et al., 2014).”
Although we are not yet able to dictate languages or learn how to ace the MCAT while asleep, the possibilities of research in this particular topic are endless. Both Paller and Sara indicated the importance of auditory cues in enhancing memory consolidation in slow-wave sleep and the measurement of sleep spindle oscillation activity during this stage. Although clinical study of sleep learning is still quite controversial in its own, I would like to think that this research will someday be able to help us, especially those suffering from age-related memory decline.

References:
Paller, Ken A. et al. (2017) “Sleeping in a Brave New World: Opportunities for Improving Learning and Clinical Outcomes Through Targeted Memory Reactivation” Sage Journals. http://journals.sagepub.com/doi/abs/10.1177/0963721417716928
Sara, Susan J. Journal of Neuroscience 18 January 2017, 37 (3) 457-463; DOI: https://doi.org/10.1523/JNEUROSCI.0297-16.2017
Bellesi M, Riedner BA, Garcia-Molina GN, Cirelli C, Tononi G (2014) “Enhancement of sleep slow waves: underlying mechanisms and practical consequences.” Front Syst Neurosci 8:208, doi:10.3389/fnsys.2014.00208, pmid:25389394

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