The Real-life Applications of Targeted Memory Reactivation during sleep

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5808124/bin/fnhum-12-00028-g001.jpg

Sleep has long been known by scientists and the public to play an important role in memory and have certain effects on our tendencies towards certain behaviors during consciousness, as well as our brains’ abilities to fortify fragile short-term memories into long-term memories. Though their effectiveness has not been scientifically proven, many companies have advertised their own products that play subliminal messages during sleep to help consumers quit addictive behaviors such as smoking. Targeted Memory Reactivation (TMR), the basis of Ken A. Paller and Renee E. Shimizu et. al’s studies, has been proven to be more crucial to sleep learning, as it reiterates information learned during consciousness rather than introducing new information during sleep, as addiction-reduction recording companies do.  

Paller’s article, “Sleeping in a Brave New World: Opportunities for Improving Learning and Clinical Outcomes Through Targeted Memory Reactivation,” explains the positive effects of sleep on memory consolidation. By playing auditory cues while participants performed memory formation tasks and then playing the same cues while the participants slept, memory retention and learning curves were shown to be dramatically increased in comparison to control participants who had not received TMR. Paller references a study by Staresina et. al. wherein slow oscillations (SOs), thalamocortical sleep spindles, and hippocampal sharp-wave ripples were crucially involved in memory consolidation during sleep.  

A study conducted by Shimizu et. al in Frontiers in Human Neuroscience also emphasizes the role of SOs, sleep spindles, and sharp-wave ripples occurring during Non-REM sleep that help consolidate declarative memories formed during consciousness. While Paller’s study focuses on the role of TMR to help consolidate memories associated with skill and habit learning or bias reduction, Shimizu’s study focuses on spatial and directional navigation improvement using the same mechanism. In this way, Paller and Shimizu et. al have opened a discussion about the diverse applications of TMR on learning and memory.

The participants of Shimizu et al.’s study were made to navigate the streets of a virtual city (using Oculus VR headsets) while auditory cues (such as a the sound of a pipe dropping while participants crossed the street in an industrial district) were played in the background. The same auditory cues were then played again while participants slept. The researchers developed a closed-loop TMR mechanism (CL-TMR) which only played the cues at times when participants’ brains produced electrical signals (through EEG recordings) that showed DUPT (down-state to up-state transitions), indicating the occurrence of slow-wave sleep spindles. The results of the study showed that these specifically timed auditory cues were more effective in improving memory consolidation, as participants who underwent CL-TMR later found destinations in the virtual city more quickly than those who did not receive CL-TMR. These findings were eye-opening, as I have personally struggled with directional cues and navigational memory, and would find Shimizu et. al’s application of CL-TMR to be very useful in my own life.  

As we can see, both researchers singled out the same sleep patterns during NREM (sharp-wave ripples, SO’s, and spindles), but Shimizu et. al went a step further through his development of the CL-TMR software to single out DUPTs (down-state to up-state transitions) during a participant’s sleep cycle. The real-life applications of this technology have been shown to be very diverse, as Paller introduced the cognitive and behavior-reinforcement functions of TMR, and Shimizu et. al found the navigational memory improvement functions. Therefore, CL-TMR technology has the ability to one day be commonly used and be effective for students or directionally-challenged individuals like myself.

Shimizu's et. al's article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5808124/