Q1) In the video, we learn how sleep can help consolidate memory. How does the information in the video compare to the hypothesis stated in the paper?
In the video, the presenters state that when people sleep, the brain reviews what they have learned and strengthens the memories. When people sleep, the brain gets modified to function better the next day ( NOVA Science NOW: 37- Sleep, 2012). For example, after one night's sleep or after taking a nap, an individual can better recognize visual patterns and solve maths problems. Also, after sleeping, a person can type numbers faster and more accurately. This indicates that sleep enhances memory so that an individual can function better the next day.
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The author notes that the hippocampus plays an imperative role in memory. The specific areas in the hippocampus that are activated when memorizing materials are the same regions that turn up when a rat is asleep. Essentially, when the rats fall asleep, the patterns of the brain that were active when memorizing events during the day will be replayed in the same sequence and order as they were experienced when the rat is asleep ( NOVA Science NOW: 37- Sleep, 2012) . The events are, however, replayed in fast forward and quick flashes. At that time, the brain has not determined the important and not-so-essential things. As such, the brain edits some of the memories to identify the crucial factors. This fragmented replay does not only happen in the hippocampus but also occurs in the visual cortex. This means that, probably, the rats could see the activities in their sleep.
The visual cortex is part of the neocortex, which is responsible for long-term memory in humans. As such, during sleep, the hippocampus activates the neocortex through processing and replaying memory. This can be termed as a form of learning from past experiences. In this case, the sleeping brain reviews and strengthens the memories that will be stored in the long-term memory ( NOVA Science NOW: 37- Sleep, 2012). Also, the sleeping brain might identify the goals that an individual wants to fulfill and also enable an individual to gain insight. When individuals face real problems, they might “sleep on it” to gain insights into solving the problem. In this case, sleeping on it is a biological process that involves the consolidation and organization of important information in the brain. This portrays that sleep is a biological necessity, and disturbed sleep harms the ability of an individual to develop memories.
The hypothesis in the article promotes the role of sleep in enhancing memory. The author posits that non-rapid eye movement (NREM) sleep and its oscillations are essential in consolidating and recalling declarative memory. Forgetting reduces the neural resources required to enhance remembering. Also, forgetting weakens and suppresses memory representations ( Saletin, Goldstein & Walker, 2011). Forgetting is therefore associated with improved efficiency of recall. Sleep can be used to treat some episodic experiences. For instance, offline sleep is associated with increased retention of emotional memories as compared to neural memories. This portrays discriminatory processing of memories in the brain.
Q2) Saletin et al. (2011) tested their participants immediately after learning words to be remembered (R) or forgotten (F). What did this immediate test show about the level of remembering vs. the level of forgetting for the nap and no-nap groups?
The study indicated that in terms of immediate recognition, memory accuracy between the R- words and F- words were identical. Between the two groups, performance was better in the R- words than in the F- words. Moreover, the difference in memory accuracy between the R- words and F- words were not different between the two groups ( Saletin, Goldstein & Walker, 2011). Overall, the study indicated that before sleep or wake offline manipulation, the encoding level for each word was similar. The task was associated with increased directed forgetting in both groups. The magnitude of forgetting due to manipulation was similar in the two groups.
Regarding delayed free recall, the findings indicated that the two groups recalled more R- words than F- words after the sleep and wake patterns. However, the Nap group recalled more words as compared to the No- Nap group. Besides, the Nap group portrayed preferential recall for R- words without any enhancement to recall F- words ( Saletin, Goldstein & Walker, 2011). This indicates that sleep did not facilitate the memorization of all items. Instead, sleep increased the participant's ability to recall for words meant for recall but did not enhance memory for words meant to be forgotten. This indicates the specificity of memory based on prior waking instruction.
In terms of sleep physiology association, the study found a strong relationship between fast sleep spindles and the efficiency score for directed forgetting in various posterior electrode sites (PowerPoint Presentation for Biopsychology by John P. J. Pinel). For example, the P3 situated on the left superior parietal lobe, and which is related to the processing of episodic memory, portrayed significance. On the other hand, slow sleep spindles did not indicate such associations. Besides, the fast sleep spindles facilitated the recall of R- words and F- words independently and in opposing directions.
Q3) After a period of either napping or no-napping, the participants were tested on their ability to freely recall the words. How did the two groups (Nap vs. No-Nap) compare in their abilities to recall the R vs. F words? How did the results of the nap group correlate with the electrophysiological results? How is this work important?
After periods of sleep and wake patterns, the Nap and No- Nap groups recalled more R- words than F- words. The study also found a significant effect on the group where the Nap group recalled more words than the No- Nap group. The benefit of sleep in the Nap group did not result from an equal improvement in the R and F- words. In addition, the individuals in the Nap group portrayed a preferential recall of the R- words compared to the No- Nap group ( Saletin, Goldstein & Walker, 2011). This benefit on the Nap- group occurred in the absence of enhanced recall of the F- words. This indicates that sleep did not facilitate the recall of all items but rather, sleep offered a better sleep advantage for the words that had previously been cued for remembering but did not enhance memory for the items that were meant to be forgotten. This portrays the specificity of the brain in enhancing memory after waking instruction.
Based on sleep physiology association, the study found a strong and significant relationship between fast sleep spindles and the directed forgetting efficiency score in most locations within the posterior electrodes ( Saletin, Goldstein & Walker, 2011). For instance, the findings indicated that the p3, which is located in the left superior parietal lobe and related to episodic memory processing, indicated significance. At the same time, the slow sleep spindles did not portray any significant associations.
This study is essential since it portrays the relationship between recalling material during sleeping and waking periods. The findings demonstrate that sleep, as opposed to wakefulness, selectively enhances the remembrance of words previously cued for recall instead of the ones that were meant to be forgotten. The findings of the study add information to the literature suggesting that sleep is associated with enhanced memory.
References
PowerPoint Presentation for Biopsychology by John P. J. Pinel
NOVA Science NOW: 37- Sleep. (August 9, 2012). YouTube. https://www.youtube.com/watch?v=nn6gnhg71hE&t=626s
Saletin, J. M., Goldstein, A. N. & Walker, M. P. (2011). The role of sleep in directed forgetting and remembering in human memories. Cerebral Cortex. 21: 2534- 2541. https://doi.org/10.1093/cerecor/bhr034
