Posted comment on ´ A 10 minute rest can boost memory like sleep` by J. Hamzelou and published in New Scientist 9th January 2016 issue 3055 p. 9.
In her article Hamzelou reported on the findings of Dewar that brain memory consolidation may occur during the wake cycle as well as the sleep cycle. Dewar found that individuals who had a 10 minute rest after hearing a story remembered 10 per cent more of it a week later than those individuals who engaged in a non-relevant task. This indicated improved long-term memory from resting after learning. Spatial memory appears to be affected in the same manner with a 10 per cent increase in orientation ability after a post-learning rest. Individuals suffering from amnesia too found a similar positive recall advantage. In a study by Dewar, 8 out of the 12 subjects with amnesia who remembered nothing from a learnt novel word list under normal circumstances, saw improvements of 30-80% in recall ability if a 9 minute rest period was included after learning.
Therefore, according to Dewar`s observations it appears that there are benefits of a post-learning rest on long-term memory recall. For people suffering from insomnia, Gaskell hypothesises that a lack of sleep may be compensated to some degree by relaxing instead since some memory consolidation will occur. Dewar hypothesizes that overstimulation may be the cause of amnesia and hence by reducing the level of information going in then new memories can be formed albeit at a lower level than in normal conditions.
Therefore, Hamzelou concludes on the basis of the observations given in her article that when learning is necessary then a 10 minute rest after the encoding period can increase the ability to recall the material long-term.
This article reports on the benefit of wakeful rest in the case of learning and recall of word lists and there are other examples showing similar benefits eg spatial learning. What makes this article and work in this area interesting is that in the past it has been assumed that consolidation of long-term memory takes place primarily in sleep. During N-REM and REM sleep periods there is memory stabilization and consolidation, a reported shift from the hippocampus to the cortical regions requiring cholinergic activity for long-term memories, reactivation of memories using the hippocampus and post cortical regions as well as the molecular replenishment at the synapse in preparation for the next waking period. Hence, sleep deprivation is known to influence brain memory learning and recall as well as other cognitive capabilities, eg attention, working memory. The studies reported in Hamzelou`s article support the view that memory consolidation can also occur when the individual is not asleep (not even the so-called 10 minute power nap), but rather in a period of wakeful rest.
This does not appear much of a surprise since memory formation to some extent must occur even in the absence of sleep otherwise short-term memories would not be possible, but these studies show an increase in long-term memory recall performance. Hence, it is assumed that this benefit occurs from the removal of ´competing` material thus promoting the memory storage processes involved in learning the target material which is in the experiments described in Hamzelou`s article, word lists. By ´removal of competing material` I mean that visual input is reduced during the wakeful rest period resulting in a robust decrease of the overall sensory input load occurring at the time. (People do this in a small way by shutting their eyes when they want to concentrate, and or learn something.) The reduction in sensory input allows non-conscious informational processing capability, working memory and biochemical storage processes to be focused on the task undertaken before the wakeful rest period began, which in this case is the learning of a word list. Ramor reported that spatial firing patterns during wakefulness correlate sharply to spatial patterns observed during gamma wave sleep indicating that the appropriate memory traces are strengthened. Denker expanded on this by showing that stimulus activation patterns reoccur spontaneously during wakeful rest periods and the frequency by which this occurs predicts subsequent memory recall performance. Therefore, it can be hypothesized that wakeful rest leads to increased long-term memory performance for the task learnt just before it by increasing the stabilization of the traces formed during its learning by spontaneously firing hence strengthening the trace patterns and by removing stimuli that would normally compete for the same cognitive capabilities.
This hypothesis may be even more applicable for the results of the study with participants suffering from amnesia. The level of memory problems is dependent in this case on the degree of severity of the amnesia, with milder cases still capable of learning and recall, but with learning slower and requiring an increased number of repetitions. Therefore, by removing competing stimuli during the wakeful rest period cognitive processes can be applied to the task at hand which would be the learning of the word list. The beneficial learning effect may also be increased by the participants desire to perform well. Since recall is related to an object`s salience (work by Fine) then the desire for success particularly by those suffering from amnesia will increase the value of the words and hence stimulate learning to a higher degree than under normal circumstances.
Although this article shows that the 10 minute wakeful rest has memory benefits, numerous sleep deprivation studies have shown the importance of proper sleep patterns. Sleep deprivation leads to attention dysfunction, working memory problems for example and we know that even in sleep, the brain is still functioning in some way (default network) and processing is occurring. For example, visual input may be reduced, but the olfactory and auditory senses are still functioning to some degree and this has been shown by smells and sounds being able to boost learning. It has also been reported that learning of new material is also possible during sleep (Berich – new memories are created in sleep linking reward and place). Therefore, the mysteries of sleep and its relationship to memory have not been fully explored and although this article indicates that short-term, wakeful rest may have benefits, it cannot take the place of normal sleep patterns.
Since we`re talking about the topic……….
……would a ´know` type experiment versus ´familiarity` type experiment show even greater memory recall benefits of the wakeful rest period after learning? Would imaging of the perirhinal cortex shown to play a role in familiarity-based object recognition show changes in firing activity after wakeful rest? Would there be a revelation effect (familiarity increase after intervening task) in this type of study if the subjects had a wakeful rest period?
……can we assume that the benefit of the wakeful rest period after learning applies also to procedural memory?