Deep – uninterrupted sleep can help boost learning names and faces


New research by Northwestern University is the first to document the effect reactivating memory during sleep has on face-name learning.

The researchers found that people’s name recall improved significantly when memories of newly learned face-name associations were reactivated while they were napping. Key to this improvement was uninterrupted deep sleep.

“It’s a new and exciting finding about sleep, because it tells us that the way information is reactivated during sleep to improve memory storage is linked with high-quality sleep,” said lead author Nathan Whitmore, a Ph.D. candidate in the Interdepartmental Neuroscience Program at Northwestern.

The paper, “Targeted memory reactivation of face-name learning depends on ample and undisturbed slow-wave sleep,” will publish Jan. 12 in the Nature partner journal “NPJ: Science of Learning.”

The paper’s senior author is Ken Paller, professor of psychology and director of the Cognitive Neuroscience Program at Weinberg College of Arts and Sciences at Northwestern. The paper was also co-authored by Adrianna Bassard, Ph.D. candidate in psychology at Northwestern.

The research team found that for study participants with EEG measures (a recording of electrical activity of the brain picked up by electrodes on the scalp) that indicated disrupted sleep, the memory reactivation didn’t help and may even be detrimental.

But in those with uninterrupted sleep during the specific times of sound presentations, the reactivation led to a relative improvement averaging just over 1.5 more names recalled.

The study was conducted on 24 participants, aged 18-31 years old, who were asked to memorize the faces and names of 40 pupils from a hypothetical Latin American history class and another 40 from a Japanese history class. When each face was shown again, they were asked to produce the name that went with it.

This is a diagram from the study
The three main stages of the experiment of Whitmore et al. (2022). First, participants learned 80 face-name associations. Next, they slept while EEG was monitored to determine sleep stage, and 20 of the spoken names were presented softly over background music during slow-wave sleep. Finally, memory testing showed superior memory due to memory reactivation during sleep, but only when sleep was undisturbed by sound presentations. Credit: Nathan Whitmore, a Ph.D. candidate in the Interdepartmental Neuroscience Program at Northwestern University.

After the learning exercise, participants took a nap while the researchers carefully monitored brain activity using EEG measurements.

When participants reached the N3 “deep sleep” state, some of the names were softly played on a speaker with music that was associated with one of the classes.

When participants woke up, they were retested on recognizing the faces and recalling the name that went with each face.

The researchers say the finding on the relationship between sleep disruption and memory accuracy is noteworthy for several reasons.

“We already know that some sleep disorders like apnea can impair memory,” said Whitmore. “Our research suggests a potential explanation for this — frequent sleep interruptions at night might be degrading memory.”

The lab is in the midst of a follow-up study to reactivate memories and deliberately disrupt sleep in order to learn more about the relevant brain mechanisms.

This new line of research will let us address many interesting questions — like whether sleep disruption is always harmful or whether it could be used to weaken unwanted memories,” said Paller, who also holds the James Padilla Chair in Arts & Sciences at Northwestern. “At any rate, we are increasingly finding good reasons to value high-quality sleep.”

Sleep is essential for normal physiological functionality. The panel of National Sleep Foundation suggests sleep durations for various age groups and agrees that the appropriate sleep duration for young adults and adults would be 7–9 hours, and for older adults would be 7–8 hours (Hirshkowitz et al., 2015).

Today, people sleep for 1–2 hours less than that around 50–100 years ago (Roenneberg, 2013). Millions of adults frequently get insufficient sleep (Vecsey et al., 2009), including college and university students who often report poor and/or insufficient sleep (Bahammam et al., 2012; Curcio et al., 2006; Hershner and Chervin, 2014). During the COVID-19 pandemic, sleep problems have been highly prevalent in the general population (Gualano et al., 2020; Jahrami et al., 2021; Janati Idrissi et al., 2020) and the student community (Marelli et al., 2020). Poor and insufficient sleep is a public health issue because it increases the risk of developing chronic pathologies, and imparts negative social and economic outcomes (Hafner et al., 2017).

Like sleep, mood and emotions determine our physical and mental health. Depressive disorders have prevailed as one of the leading causes of health loss for nearly 30 years (James et al., 2018). Increased incidence of mood disorders amongst the general population has been observed (Walker et al., 2020), and there is an increase in such disorders amongst students (Auerbach et al., 2018). These have further risen during the COVID-19 pandemic (Son et al., 2020; Wang et al., 2020).

The relationship between sleep, mood and cognition/learning is far more complex than perceived. Therefore, this review aims to recognise the interrelationships between the aforementioned trio. It critically examines the effects of sleep and mood on cognition, learning and academic performance (Fig. 1).

Furthermore, it discusses how various regulatory factors can directly or indirectly influence cognition and learning. Factors discussed here are age, gender, diet, hydration level, obesity, sex hormones, daytime nap, circadian rhythm, and genetics (Fig. 1). The effect of sleep and mood on each other is also addressed. Pictorial models that hypothesise learning on an emotion scale and vice-versa have been proposed.

Fig. 1: Complex relationship between sleep, mood, and learning.

Effect of sleep on cognition and academic performance

Adequate sleep positively affects memory, learning, acquisition of skills and knowledge extraction (Fenn et al., 2003; Friedrich et al., 2020; Huber et al., 2004; Schönauer et al., 2017; Wagner et al., 2004). It allows the recall of previously gained knowledge despite the acquisition of new information and memories (Norman, 2006). Sleeping after learning acquisition regardless of the time of the day is thought to be beneficial for memory consolidation and performance (Hagewoud et al., 2010). Therefore, unperturbed sleep is essential for maintaining learning efficiency (Fattinger et al., 2017).

Sleep quality and quantity are strongly associated with academic achievement in college students (Curcio et al., 2006; Okano et al., 2019). Sufficient sleep positively affects grade point average, which is an indicator of academic performance (Abdulghani et al., 2012; Hershner and Chervin, 2014) and supports cognitive functionality in school-aged children (Gruber et al., 2010). As expected, insufficient sleep is associated with poor performance in school, college and university students (Bahammam et al., 2012; Hayley et al., 2017; Hedin et al., 2020; Kayaba et al., 2020; Perez-Chada et al., 2007; Shochat et al., 2014; Suardiaz-Muro et al., 2020; Taras and Potts-Datema, 2005).

In adolescents aged 14–18 years, not only did sleep quality affect academic performance (Adelantado-Renau, Jiménez-Pavón, et al., 2019) but one night of total sleep deprivation negatively affected neurobehavioral performance-attention, reaction time and speed of cognitive processing, thereby putting them at risk of poor academic performance (Louca and Short, 2014).

In university students aged 18–25 years, poor sleep quality has been strongly associated with daytime dysfunctionality (Assaad et al., 2014). Medical students tend to show poor sleep quality and quantity. In these students, not sleep duration but sleep quality has been shown to correlate with academic scores (Seoane et al., 2020; Toscano-Hermoso et al., 2020).

Students may go through repeated cycles wherein the poor quality of sleep could lead to poor performance, which in turn may again lead to poor quality of sleep (Ahrberg et al., 2012). Sleep deprivation in surgical residents tends to decrease procedural skills, while in non-surgical residents it diminishes interpretational ability and performance (Veasey et al., 2002).

Such effects of sleep deprivation are obvious because it can impair procedural and declarative learning (Curcio et al., 2006; Kurniawan et al., 2016), decrease alertness (Alexandre et al., 2017), and impair memory consolidation (Hagewoud et al., 2010), attention and decision making (Alhola and Polo-Kantola, 2007). It can increase low-grade systemic inflammation and hinder cognitive functionality (Choshen-Hillel et al., 2020).

Hippocampus is the region in the brain that plays the main role in learning, memory, social cognition, and emotion regulation (Y. Zhu et al., 2019). cAMP signalling plays an important role in several neural processes such as learning and memory, cellular excitability, motor function and pain (Lee, 2015). A brief 5-hour period of sleep deprivation interferes with cAMP signalling in the hippocampus and impairs its function (Vecsey et al., 2009). Thus, optimal academic performance is hindered, if there is a sleep disorder (Hershner and Chervin, 2014).

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Source: Northwestern University


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