2021 Honorable Mention – Samuel Uribe-Botero
A Primer for Memory
Sleep takes up so much of our life, and yet we know very little about its functions. It is believed to promote cellular recuperation, physical growth (pituitary glands) and heighten mental functioning, but we have only begun the research. Research sleep as more than just a passive state of physical recuperation began around 1953. It was only after Eugene Aserinsky discovered REM-sleep, which is characterized by its brain wave frequency that resembles wakefulness patterns. He stumbled upon these higher activity brain waves when testing an EEG machine on his son. We now know sleep has four stages: three Non-REM and REM-sleep. Through the three NREM stages, the brain experiences sporadic brain waves causing hypnagogic sensations, sleep spindles or rapid brain activity, and finally the slow, restful Delta waves. During REM, our motor cortex is highly stimulated, while the brain stem blocks the activity and relaxes the body. This is when daily memory processing and other related mental functioning may happen.
Neuroimaging studies done on animals have predicted that sleep helps induce the declarative, or explicit, memory system (hippocampus-mediated memory), which are memories that are consciously recalled such as faces, space, or places. This led researchers back in the mid 2000’s, like Ellenbogen et al., to aim at demonstrating that sleep actually is important for the neurobiology of memory consolidation, even though there was limited data on this connection for humans at the time. According to their findings, they became one of the first research labs to conclude that the consolidation of memories, or these abstract forms of internal visualization or auralization we think of as explicit memories, are aided by sleep (Ellenbogen et al. 2006). We know this is done through the Hippocampus during REM sleep.
So, what are the brain waves like during REM sleep? To start, these brain waves are a representation of a synchronized or unsynchronized firing of many neurons. The waves we see in REM sleep are actually desynchronized oscillations that resemble the pattern seen during wakefulness. These are different from the very slow Delta waves that are seen in the NREM sleep. Particularly in the Hippocampus, where memories seem to be consolidated, there are theta wave rhythms that oscillate at a frequency of 3-10 Hz. Just as an interesting side note, if we were to convert that frequency range into air molecule oscillations, or in other words sound, it would be the range where a listener would pick up the top of a bass line for example, or the lower body of a synth pad.
One artistic place of interest in this field for me is the creative outcomes from sleep and its interplay with memory. Wagner wrote the beginning of Das Rheingold after dreaming of flowing water forming into Eb broken triads and Ramanujan dreamt of novel identities and equations throughout his short life. I spoke to Dr. Blake Porter about this interest, and he gave me a recording of neurons firing in a sleeping labrat. From those recordings I was able to base my sonoric landscape as an immersion into an imaginary hierarchy of memories flowing through the labrats hippocampus. This incredible journey is once again represented with a few mere, unsynchronized clicks and taps.
Ellenbogen, Jeffrey M., et al. “Interfering with Theories of Sleep and Memory: Sleep, Declarative Memory, and Associative Interference.” Current Biology, vol. 16, no. 13, 2006, pp. 1290–1294., doi:10.1016/j.cub.2006.05.024.
Sam McKenzie, Andrea J. Frank, Nathaniel R. Kinsky, Blake Porter, Pamela D. Rivière, Howard Eichenbaum, Hippocampal Representation of Related and Opposing Memories Develop within Distinct, Hierarchically Organized Neural Schemas, Neuron,Volume 83, Issue 1, 2014, Pages 202-215, ISSN 0896-6273.