Memory consolidation is the process whereby new memories are encoded, strengthened, and integrated into existing knowledge; these recesses are termed stabilization, enhancement and integration, respectively (Walker, Stickled, Also, Gab, & Scholar (2005). It is thought that memory consolidation occurs during sleep whilst there in no incoming information (Marshall & Born, 2007). The brain cannot simultaneously manage incoming information and long-term memory storage, as these processes use the same neuronal network capacities.
Therefore, it has been suggested that one of the primary functions of sleep if for memory consolidation, as it produces ideal conditions for storage to occur Marshall & Born, 2007). This essay will evaluate evidence suggesting memory consolidation occurs when we asleep, and determine to what extent this suggests it is one of the primary roles of sleep. Originally researchers believed ERM sleep was primarily involved in sleep consolidation, as the theta waves characteristic of ERM sleep have been shown to facilitate learning; this suggested ERM would be heavily involved in memory consolidation too (another citation, Siegel, 2001).
However, more recently there has been increasing evidence for the role of different sleep stages and EGG characteristics. Furthermore, these stages of sleep are thought to have their own function for the consolidation of specific types of memory (Gags & Born, 2004). These specific types of memory can be grouped more into either declarative or non- declarative memories (Oilman, 2004). Declarative memories are explicit and can be consciously recalled, for example memory for events and facts. Non-declarative, on the other hand, is usually memory for implicit knowledge, like skills or motor learning (Oilman, 2004).
The hippopotamus is thought to be heavily involved in the installation of declarative memories (Disneyland & Born, 2010). It does this by binding together the same pattern of cortical activation that takes place during encoding and transferring it to noncommercial areas during sleep. Conversely, this process does not occur during the consolidation of non-declarative memories. Non- declarative memories are thought to be supported by ERM which occurs independently of Hippocratic transfer (Disneyland & Born, 2010). Despite these claims, the roles of these sleep stages are thought to be unclear as there are many inconsistent findings.
For example, SSW has been found to improve non- declarative memories as well as declarative memory (Stickled et al. , 2000). Walker et al. , (2002) used a motor learning task to determine whether any sleep-related effects Critically Evaluate the Evidence That Memory Consolidation Is One of the Primary Functions of Sleep By athletes modest 20% improvement was observed in participants who had slept after training, whereas no improvement could be seen over the equivalent time awake. This improvement correlated with the SSW in the fourth quarter of sleep, contradictory to life (Walker et al. , 2002).
Further memory facilitation from SSW in non-declarative sleep can be seen in motor rotation adoption tasks (Huber, Gaillardia, Massing, & Toni, 2004). This study involved participants using a digital tablet to draw a straight line whilst overcoming an invisible force. As with the previous study, improvements were sleep-dependent and associated with EGG oscillations characteristic of SSW (Huber et al. , 2004). Taken together with the bulk of previous findings demonstrating the role of ERM sleep in non-declarative memory, the findings above show how role of these stages of sleep in still unclear.
However, most importantly the fact the improvements in these are sleep-dependent show that sleep does seem to have some role in the consolidation of non-declarative, even if a modest one. This is evidence is important as it provides an argument against the main argument against sleep related memory consolidation, that it Just occurs because of a passage of time. In addition to the experimental evidence exploring motor control, there is body of research using discrimination tasks to explore consolidation of non- declarative memories. However, these findings have been less conclusive.
For example Stickled et al. , (2000), asked participants to identify whether the central letter of a grid was a T or an L, and whether three lines were horizontal or not (visual discrimination tasks). There were improvements in task performance in the participants who had slept since the first set of trials (13-22. 5 hours later) compared to those performing the task 3-9 hours after without sleep (Stickled et al. , 2000). However, unlike the motor related tasks, these findings showed improvements that occurred independent of sleep.
Similarly, a study using an auditory discrimination task also demonstrated improvements independent of sleep (Athenian, Canters, & Stickled, 2004). Subject’s attention was diverted whilst they listened to auditory stimuli curing which event-related potentials were measured. They found performance improved over 72 hours, even when participants were sleep-deprived, suggesting sleep was not necessary for consolidation. However, the brain processes responsible for shifting attention to auditory stimuli failed in the sleep deprived participants.
This suggests sleep is necessary for automatic perceptual coordination and further supports its role in memory consolidation of non- declarative memories (Athenian, Canters, ; Stickled, 2004) Not only does the evidence above support the importance of sleep consolidation for non-declarative memories, but it also provides evidence for the consolidation of memories across modalities, for example sound and vision. On top of this, Reach, Bјcell, Gags ; Born Total number of stars, (2007) examined the effects of sleep on memory consolidation using dour cues.
Participants were asked to memorize the location of card-pairs, whilst exposure to rose dour. Participants were then instructed to sleep whilst unknowingly being exposed to the roses again; these participants had significantly higher memory recall compared to those who had slept without the rose dour exposure. This suggests reactivation of the same doors during encoding can facilitate memory consolidation. Furthermore, fem. revealed significant Hippocratic mentioned earlier, these effects are restricted to declarative memories and support the idea that SSW is involved in declarative memories (Reach, et al. 2007). However, generally, experimental evidence for declarative memory has produced less inclusive findings than for those for non-declarative, with earlier studies finding almost no significant findings (Stickled,). Nonetheless, findings have been more successful since looking specifically at SSW, like the previous study (Reach, et al. , 2007). As well as experimental research exploring declarative memory, SSW age- related memory deterioration can be observed (Sculling, 2012).
Sculling, (2012) found the positive effect SSW in episodic memory diminished with age, as older participants did not experience the same memory improvements from SSW, as young people did. Additionally, older people experienced negative effects of SSW deprivation compared to young people (Sculling, 2012). However, although human studies suggest SSW is associated with declarative memory consolidation, rat studies imply ERM is important, further complicating the roles of sleep stages in memory consolidation (Stickled et al. 2000). This contradiction may be explained by a study in humans that suggests ERM contributes to the consolidation of declarative memories with emotional content (Wagner, Gags and Born, 2001). In this study, participants recall for notionally negative passages improved after 3 hours of ERM-rich sleep. This was thought to be because ERM sleep activates important areas of limbic system involved with emotion, for example the amazedly (Wagner, Gags ; Born, 2001).
Therefore, rat studies that demonstrate an association between ERM and declarative memory may actually Just be reflecting an association between ERM and the rat’s emotional stress (Stickled et al. , 2000). These findings can be supported to some extent by comparative ecological studies exploring correlations between sleep characteristics and neurophysiology/ecological patterns. Chaplin’ et al,. (2007) found evolutionary increases in the size of the amazedly are associated with corresponding increases in NORM sleep durations; the hippopotamus also showed a borderline significant correlation.
These results are consistent with majority of new research suggesting NORM sleep in associated However…. We can conclude from the above evidence that the stages of sleep involved in memory consolidation are unclear. However when examine sleep in general and don’t look at sleep stages involved in emotional aspects of declarative memory, there is still evidence to suggest long term memory improvements. Wagner, Hillside, Reach, & Born, J. (2006) asked participants to learn neutral and emotional passages immediately before staying awake or sleeping.
After four years, they contacted the participants; there was a significant different in recall of the emotional passages compared to those who had remained awake. Together, these findings suggest that sleep consolidation can occur for emotionally salient memories, in spite other evidence for declarative memory consolidation or the sleep stages underlying them being unclear. Further justification in the argument to rethink the way we study sleep is provided by recent endings showing how certain EGG characteristic have been found to associate with sleep consolidation.
For example, sleep spindles, occurring in stage 2 NORM, have been correlated with successful recall of word pair associations (Scab’s et al,. 2004; Clemens, Feb., ; Halls (2005). This evidence also goes someway to explaining a drugs suppress ERM sleep; however most evidence has found no evidence to suggest there are any negative effects on cognitive functions, such as memory (Verses, 2004; Thomson, 1991; Wyatt et al. , 1971). This suggests ERM sleep is not crucial for memory consolidation.
However, Watts , Gritting , Swearing ; (2012) examined the effects of the antidepressant drug DIM on rat’s spatial and procedural memory; this is found to suppress a transitional stage to ERM rich in spindles (TRY) as well as ERM sleeps. Findings showed that enhancement occurs during hippopotamus-dependent memories and that stabilization occurs during TRY, suggesting further evidence for a role for sleep spindles. Furthermore, Stickled 2000, pointed out that it wasn’t suspiring that these previous studies failed to show effects as most if them tested declarative memory, which we would not expect ERM to affect.
Despite this the evidence provided here shows that stages. We would do better to inner stages and characteristics of sleep and look at the effects of deprivation overall to understanding whether it is one of the primary functions of sleep. One of the most convincing arguments that sleep consolidation is one of the primary roles of sleep is that fact that sleep deprivation affects memory consolidation, suggesting there is some necessary function to sleep. For example, … Examined the effects of sleep deprivation on memory consolidation in rats using the Morris Water Maze, which sees non-declarative and deliberative memory.
The rats were sleep deprived after training for contextual and cued fear conditioning. They found that sleep deprivation 0-5 h after training impaired memory consolidation only for contextual fear conditioning. However, some researchers would argue this actually Just reflects the effects of stress on cognition. For example, the restoration theory of sleep states that it is necessary for maintenance and to restore energy, with studies have shown a relationship between wound healing, immune system functioning, growth hormone levels and the removal of free radicals in the brain.
For example, sleep deprivation has been reliably linked to increasing stress levels, shown by increases in sociolinguistics, which have been shown to affect cognition. Despite this, there are a few studies, whereby we can rule out the effects of stress. Garishness-Goal et al. , (2010) studied 54 children with obstructive apneas, to examine the impact this has on their visual memory. Compared to controls, these children experienced poor performance on both long term and short term memory recall.
This suggests the disturbance OSHA causes to the stages of sleep disrupts memory consolidation. Furthermore the fact hat hibernating animals sleep afterwards, cannot be explained by either the sleep consolidation or restoration theory. The evidence presented above provides a great deal of support for the idea that sleep consolidation occurs during sleep, particularly studies testing non-declarative memory. However, this idea that this is the primary role of sleep remains controversial.