Download Information Consolidation Theory

Cognitive Approach to sleep
Cognitive psychologists study all of the mental actions performed by people (and sometimes
animals). It includes the way in which we create concepts, solve problems, make decisions, and
form judgments, for example:




if I say the phrase "gold digger", what attributes come to mind? (creating concepts);
how would you deal with a friend who borrowed £100 and refuses to pay you back?
(solving problems);
would you work a potentially hazardous job if it paid £100k per year? (making
decisions);
what was the first thing you thought about when you saw your teacher on the first day
of class? (forming judgments)
Information processing
All of the above are examples of information processing, which is what a computer does. In
fact, the information processing that we perform in our minds is sometimes compared to the
way in which a computer works - this is called a computer analogy. There is a branch of
computing science devoted entirely to this idea which is called artificial intelligence.
Information Consolidation Theory of sleep
One theory of the function of sleep and dreams from an information processing perspective is
the information consolidation theory of sleep, which is based on cognitive research. You may
have heard of this theory, which suggests that the function of sleep is to process information
that has been acquired during the day, so we are better prepared for the day to come.
There is also compelling evidence (e.g. Born and Wilhelm, 2011) that a function of sleep may
be to support the formation of long-term memory. The idea is that memories are temporarily
stored in short-term memory (in a part of the brain called the hippocampus), then gradually
get transferred to a long-term memory store, situated in the neocortex, or are forgotten. It is
during sleep that this transfer from short-term to long-term memory happens, specifically
deep (nREM) sleep. The implications of this are that without good quality sleep, we would be
unable to function properly during the day. If you think about it, we are our memories - they
form our consciousness. Without the memory consolidation function that sleep provides, we
would not form long-term memories, which would affect our sense of self. Support for this
idea stems from a number of sleep deprivation studies demonstrating that a lack of sleep has
a serious impact on the ability to recall and remember information.
Schemas, sleep and dreams
One way in which information may be organised in sleep could be through the development
of schemata. A schema is pre-existing mental structure, acquired on the basis of experience.
Originally proposed by Bartlett, Piaget suggested that schema is the mechanism by which
children develop their understanding of the experiences they learn about and encounter. Once
developed, the schema then functions to guide our behaviour in the future. For example, we
develop a schema for eating behaviour at a young age, which likely runs a bit like this.
1. You hear someone (mum, dad, brother, sister) shout "dinner time";
2. You (reluctantly?) leave your computer game and go downstairs;
Cognitive Approach to sleep
3.
4.
5.
6.
You sit at a table, which is laid with plates, cutlery, sauces, etc.
Food is brought to the table.
You eat the food with a fork, knife, spoon, etc.
You fight with your brother/sister/dog.
You may have developed a different schema, which involves plates being on laps and eating in
front of the TV. Whichever schema you have developed for eating, it will help you to know
what to do, until it becomes automatic.
So far, so good, but now your parents take you to a restaurant. The eating schema you have
developed, and which has served you very well up to now, will simply not do in this situation.
You need to develop another schema; in the meanwhile, however, you feel insecure, being
afraid you will use the wrong fork and/or knife, or spill things over yourself, which wasn't such
a big deal at home, but there are stranger here who will judge you!
What schema may you now develop for eating in restaurants? Once this schema has
developed, it will guide your behaviour the next time you go to a restaurant. You will expect
menus, being greeted by waiting staff, etc.
There is much research evidence (e.g. Durrant et al, 2011) that sleep helps the assimilation of
newly formed information, if it is compatible with an existing schema. This would mean that,
in the restaurant scenario, you would learn the new information more quickly because you
already have a similar schema for eating at home: although there are differences, there are
many similarities, too.
Durrant et al have found that sleep facilitates the assimilation of new information, probably
because neurons associated with the new information triggers the firings of neurons in the
related schema. This happens over and over again, in a loop, during sleep, so the new memory
is both strengthened and incorporated into the schema. It happens even faster if there are
many layers of overlap between the two (or more) schemas. Of course, this process happens
during wakefulness, too, but Durrant's and others' research has shown that it happens more
efficiently and quickly during sleep. Short naps of 90 minutes (nREM) after learning something
new has the same effect. A good reason for daytime napping!
The evidence for the link between sleep and its function to aid cognitive processes is vast. It
also supports the notion, mentioned earlier, that the hippocampus is highly implicated in the
processing of memories, particularly long-term memories. It also confirms the importance of
slow-wave sleep (deep sleep) to our wellbeing. Case study evidence, like Tripp and Gardner,
also confirm the importance of sleep, so supporting evidence can be found in real life as well
as in laboratories.
Much of the early research in this area used rats as subjects, which is unethical, and there is
the problem of whether we can generalise the findings from rats to humans, whose cognitions
are much more complex. The laboratory findings are undermined by the artificiality of the sleep
which is likely to be produced in sleep laboratories, which usually involve having equipment
attached to the body, often the head.
Cognitive Approach to sleep
Try it out for yourself: after re-read the "Information consolidation theory of sleep", explained
previously in this section, and then read over other theories on the function of sleep explained
previously in the introduction to this topic (the restoration theory, the ecological theory and
the reorganisation theory). Then sleep on it. You should find that as you have begun to develop
a schema for explanations of sleep, these new theories will be relatively easy to pick up. Once
you have done this, re-read the section on the "Information consolidation theory of sleep" to
remind yourself of why this happened.
Summary of the Approach
Like all approaches and theories in psychology, the cognitive approach has strengths and
limitation.
Strengths
Weaknesses
Reductionist: it could be argued that the approach
Scientific approach: the method used most is the
ignores influences other than cognition on
laboratory experiment.
behaviour, such as hormonal influences.
Many useful applications: the cognitive approach
has given us many useful treatments, such as
Cognitive Behavioural Therapy (CBT) for
depression. Studies on eye witness testimony
have influenced our judicial system.
Low ecological validity: although the approach is
scientific, laboratories are not where we usually
use our memories, perceptions, language etc. This
makes the results of studies difficult to generalise
to the real world.
Much scientific support: there are many studies
that support the notion that cognition affects
behaviour, such as those on memory.
Researchers at the University of California (Mander et al, 2013) have found a link between a
deterioration in memory function in the elderly and a deterioration in a part of the brain
associated with the transfer of short- to long-term memory.
It appears that when we are young, deep, restorative sleep (NREM) functions to transport
memories from the hippocampus (where short-term memories are stored) to long-term
storage in the prefrontal cortex. However, a reduction in deep sleep episodes in the elderly
leads to memories being 'stuck' in the hippocampus so longer term storage becomes
problematic.
Deep sleep episodes have been found to be generated by the brain's middle frontal lobe, and
it may be that deterioration of this lobe in old age results in this difficulty in transferring
memories from short- to long-term storage.
Mander et al tested the memory of 18 healthy young adults (mostly in their 20s) and 15 healthy
older adults (mostly in their 70s) after a full night's sleep. Before going to bed, participants
learned and were tested on 120 word sets that taxed their memories.
Cognitive Approach to sleep
As they slept, an electroencephalographic (EEG) machine measured their brain wave activity.
The next morning, they were tested again on the word pairs, but this time while undergoing
Magnetic Resonance Imaging (fMRI) scans.
In older adults, the results showed a clear association between the degree of brain
deterioration in the middle frontal lobe and reduced deep sleep episodes. On average, the
quality of their deep sleep was 75% lower than that of the younger participants, and their
memory of the word pairs the next day was 55% worse.
Meanwhile, in younger adults, brain scans showed that deep sleep had efficiently helped to
transfer memories from the short-term storage of the hippocampus to the long-term storage
of the prefrontal cortex.
What can you conclude from this research about the link between sleep and memory?
A conclusion would be that memory decline in the elderly is caused by a deterioration in the
pathway in the brain between the hippocampus (where short-term memories are stored) and
the parts of the pre-frontal cortex associated with long-term memory storage. This
deterioration is caused, in turn, by a reduction in the quality of sleep, particularly in deep sleep.
Other research conducted in China and the US (Yang et al, 2014) have discovered more ways
in which sleep aids memory processing.
Researchers trained mice in a new skill - walking on top of a rotating rod. They then looked
inside the living brain with a microscope to see what happened when the animals were either
sleeping or sleep deprived. Their study showed that sleeping mice formed significantly more
new connections between neurons - they were learning more.
They also found (like the Mander et al study above) that deep, slow-wave sleep was necessary
for the formation of memories. During this stage of sleep, memories were 'replayed' from the
day before, thereby consolidating them through strengthening the connections between
neurons.
The two studies described above, therefore, tell us two of the ways in which sleep influences
the processing of memories:
1. by transferring information from short-term memory (located in the hippocampus) to
long-term memory (located in the prefrontal cortex) via the middle frontal cortex;
2. by replaying memories of what happened during the day, strengthening connections
between neurons.