Download memory and forgetting extra reading

SHORT TERM MEMORY
Miller and the Magical Number 7
Miller identified the capacity of short term memory (STM) as 7 plus or minus 2 pieces of
information. This seems awfully limiting, but what consitiutes a piece of information can vary.
Essentially, a piece of information can be anything, so it is not size limited. Smaller bits of
information can be recoded into larger bits. That recoding process is called chunking.
Independently, Brown and Peterson & Peterson developed a task to examine how information is
lost from STM. This task involved holding an item in memory (such as a number, or word) and
counting backwards from a number by 3s (e.g., "405, 402, 399, 396....") at a rate of 2 numbers per
second. Evidence from experiments using this type of task, which is now known as a Brown-
Peterson task, suggested that information was lost from STM, because of decay: as more time
that passes between the initial memory and the retrieval of that memory, it becomes more difficult
to retrieve the memory, because it decays.
However, Waugh and Norman (1965) suggested that decay may not be the whole explanation for
forgetting in STM. They suggested that interference must play a role in STM forgetting, because
results from their probe digit task indicated that the presentation rate of the digits did not affect
performance.
Proactive & Retroactive Interference
If someone cannot retrieve some information, because previous information is interfering with the
retrieval, the interference is said to be proactive. It's proactive, because the material that is doing
the interfering is working forwards in time.
If someone cannot retrieve some information, because later information is interfering with the
retrieval, the interference is said to be retroactive. It's retroactive, because the material that is
doing the interfering is working backwards in time.
In the Brown-Peterson task, it was found that performance decreased across trials. It was
suggested that the decrease may be due to proactive interference, so changing the material being
kept in STM may improve performance. It did, and that improvement is known as the release from
proactive interference. This is further evidence that interference is an important factor in STM
forgetting.
One interesting study regarding release from proactive interference (PI) was done by Gardiner,
Craik & Birtwhistle (1972). They gave subjects sets of three words in a category, followed by 10
distractor words that were spelt backwards, which subjects were to say forwards, then subjects
were prompted for the first three words. After doing this for 3 trials, on the 4th trial subjects were
either given clue prior to seeing the words, prior to being prompted to recall the words, or not give
a clue. The clue indicated that the words were from a subset of the category (e.g., wild flowers or
garden flowers). Subjects receiving no clue continued to decline in recall performance, but
subjects who were given a clue demonstrated the release from PI; furthermore, that release was
similar regardless of when the clue was given (prior to seeing the words, or at the time of recall),
which suggests that people can impose some categorical knowledge on already seen information
in such a way that memory performance will improve.
Serial Position Curve
People may be asked to recall words in the order presented, which would be serial recall, or in
any order, which would be free recall. The proportion of words that are recalled can be plotted in
relation to the order they were presented in, and the result is a serial position curve.
A serial position curve will typically reveal that people recall words presented at the beginning and
end of a list better than words presented in the middle. Better recall at the beginning is an
example of a primacy effect, and better recall at the end is an example of a recency effect.
The suggested causes of primacy and recency in recall are different. For primacy, the cause is
that the early items are rehearsed enough before other items are presented to get into long term
memory (LTM), so that later they can be retrieved from there. For recency, the cause is that the
later items are still in STM, so they are just dumped out of there. Items in the middle of the list are
neither rehearsed long enough to get into LTM, nor were they presented recently enough to still
be in STM, so they are not retrieved as well as the early and late list items.
Representations in STM were thought to be acoustically coded, because presenting words that
sounded alike resulted is lower retrieval than words with had similar meanings or words that were
dissimilar. However, some have suggested that STM does represent information in relation to
semantics and imagery, as well as acoustics (see text).
Long Term Memory (LTM)
LEVELS OF PROCESSING
How information is processed influences its likelihood of getting into memory. Levels of processing
(Craik and Lockhart, 1972) suggested that the deeper material is processed the more it will be
remembered. Originally, deep was defined as meaningful. That definition works to explain results
such as Bobrow and Bower (1969), who had one group of subjects read three word sentences in
the form of noun-verb-noun, while another group is provided with the same nouns, but has to
generate the verb to connect them. The former group recalled 29% of the words, while latter group
recalled 58%.
Glenberg, Smith & Green (1977) made subjects study a 4 digit number for 2 sec, and then repeat
a word for either 2, 6, or 18 sec, after which they were to recall the number. Later, the subjects
were given a surprise recall test of the words. Over the 3 rehearsal conditions (of 2, 6, and 18
sec), recall not significantly different (11, 7 and 13 percent, respectively). However, a recognition
task showed that more repetitions of the word led to better recognition (18 sec condition > 6 sec
cond. > 2 sec cond.). These results indicate that maintenance rehearsal can improve memory, but
that whether that improvement will be seen depends on the memory task.
This leads to the issue of retrieval failure, which is the idea that people can have information in
memory that they cannot retrieve at the present time. The Tip Of the Tongue or TOT
pheonomenon is an example of this, because it is where someone knows they have the
information in memory but they are unable to produce it at this moment. Retrieval failure is
explained as the result of a difference between memories being available and accessible. All the
experiences that you have ever had may have been encoded in your memory, and if they were,
they would be part of your available memories. At any time, however, you can only retrieve a subset of those memories, and that sub-set is the memories that you have accessible.
One way to increase the accessibility of a particular memory is to duplicate the context in which
the memory was encoded. This is the principle of encoding specificity, which suggests that
likelihood of successful retrieval increases as the similarity of between the retrieval context and
the encoding context increases. According to encoding specificity, memories are encoded specific
to the context that it was first experienced. Example: diver study (above or under water), retrieval
better when the information was retrieved in the same context it was learned in rather than a
different context.
TYPES OF MEMORY
Declarative and Procedural Memory
The difference between declarative memory and procedural memory is that one is static and the
other is dynamic. That is, declarative memory is knowledge about what things are in the world,
and procedural memory is knowledge about how to do things in the world.
Examples of declarative memories would be your mother's birthday, when you last changed the oil
for your car, and how to spell oxymoron. Examples of procedural memory are how to ride a
bicycle, drive an automobile, skip, etc.
Some have suggested that procedural memory is related to tacit knowledge, which is knowledge
that individuals have but that they cannot express. That is, tacit knowledge can be possessed but
not expressed. The bicycle riding example is given in the text, where a person who can ride a
bicycle typically cannot express how they are riding the bicycle - that is, what the physical
principles are behind riding - yet they are clearly able to ride.
Some folks want to argue that this discrepancy between what we can do and what we can explain
is evidence for unconscious learning. Such folks are typically very loose with what they are calling
conscious. Also, what is the person learning when they ride a bicycle? Are the learning the
procedure to riding the bicycle or are they learning the physical principles? The former, of course,
so we should not expect them to have anything to say about the latter.
Episodic and Semantic Memory
Declarative memory can be further divided up into episodic and semantic memories, which was a
distinction identified by Endel Tulving. The text actually skips declarative memory, choosing
instead to simply discuss episodic and semantic memory directly.
Episodic memories are those that have a time stamp on them. That is, they are specific episodes
from an individual's life. Semantic memory on the other hand involves information that has lost its
time reference. Thus, a semantic memory is a bit of information that an individual knows, but the
individual has forgotten where the information from.
Tulving's view of the relationship between episodic, semantic and procedural is given. That
relationship is one of increasing encapsulation, as episodic memory is said to be dependent on
semantic memory, which is in turn dependent on procedural memory.
Implicit and Explicit memory
Schacter (1987) defined implicit memory as "information that was encoded during a particular
episode is subsequently expressed without conscious or delibrate recollection" (p. 501). There's
that conscious word again. Explicit memory is used to recall specific events, so presumably there
is some conscious effort used to retrieve the event(s).
The terms implicit and explicit memory arose from performance on different types of memory
tasks. For example, some memory tasks (e.g., free recall, or recognition) require the active recall
of information to achieve the desired goal, answer or response. Past events are directly referred
to.
Implicit memory tasks are not structured as having a single goal, nor do they make direct
reference to past events. On implicit memory tasks (e.g., stem completion), subjects are given a
task and asked to provide the best responses or those that first come to mind (typically words or
letters).
The key result is that performance on implicit memory tasks will be better after seeing a set of
words that could be answers for the test material, even though no direct reference is made to it by
the experimenter. The explanation for this is that the earlier experience with the material primed
that material for use in the later implicit memory task. Primed in the sense of activating the
memory for that information.
Moreover, there are conditions where implicit memory varies, but explicit memory does not, or
varies in the opposite way. Those results suggest that people have different memory mechanisms
for performing implicit and explicit memory tasks. This has been most clearly and suggestively
demonstrated with amnesia patients, who do not show gains in explicit memory but will show
gains in explicit memory after repeated exposure to a set of materials.
The evidence for implicit memory go back to studies of H.M., an individual who has severe
amnesia in that he cannot form new memories, although much of his old memories are intact.
Nevertheless, H.M. got improved his performance on a mirror- tracing task over a 3 day period,
but he didn't recall having done the task from one day to the next.
Evidence for implicit memory can be found in experiments using normal individuals as well.
Jacoby and Dallas (1981) showed that people were better at identifying briefly presented words
that they had seen before (old words) than at identifying briefly presented words (presentation for
35 msec, or 35/1000 of second) that they had not seen before (new words). That seems sensible,
but the words were studied in one of three conditions; some subjects considered the meaning of
the word, some the rhyme of word, and some the particular letters in the word. The study
condition affected subjects' performance on a recognition memory test in the expected way:
studying meaning led to better performance than rhyming, which was better than considering the
letters. That recognition test is an explicit memory test, because subjects are (explicitly) asked
whether they had seen each particular word before. The perceptual identification task instructions
were simply "what word are we showing you?" with no reference to the words that had been
studied. But the ability to identify a word requires memory, although it requires it implicitly, as
memory is necessary to do the task, but there is no explicit reference to a particular memory. How
the words were studied did not affect how easily they were recognized (explicit memory), but not
how easily they were identified when briefly presented (implicit memory). These results indicate
that different conditions affect explicit and implicit memory.
Elizabeth Loftus & Eyewitness Testimony
Perhaps the most significant research support for memory as a reconstructive process comes
from studies done on eyewitness testimony. Elizabeth Loftus was one of the first to examine this
area, and she is still the most prominent researcher examining it. In court, witnesses are to tell the
whole truth and nothing but the truth, so help them God. God help them. This instruction assumes
people have encoded the truth in their memories and can remember it without alteration.
However, if memory is reconstructive, then people's memories will often be remembered with
alterations.
In one of Loftus's initial studies, subjects saw film of an automobile accident (Loftus & Palmer,
1974). Subjects were asked to estimate the speed the automobiles were moving when the
accident occurred. However, subjects were asked to make that estimate in slightly different ways.
Subjects who were asked "how fast were the cars going when they smashed into each other?"
estimated that the cars were going 40 mph, while subjects who were asked "how fast were the
cars going when they contacted each other?" estimated that the cars were going 30 mph. Simply
using the word "smashed" rather than "contacted" seems to have increased people's estimates by
10 mph.
Furthermore, when later asked "do you see any broken glass?" subjects in the "smashed"
condition were more than twice as likely (about 33%) to say yes than those who had been in the
"contacted" condition (about 14%). However, there was NO broken glass in the film subjects saw.
Loftus's work indicates how influential post-event information can be on memories.
In another study, Loftus, Burns, and Miller (1978) had subjects view a series of slides depicting an
automobile accident. Later a test was given about what depicted, and in the test was either a
question that referred to a yield sign or did not refer to a yield sign. In fact, there was a slide with a
stop sign, but none with a yield sign. Later in identifying slides that they had seen before in a
forced choice situation (a slide with a yield sign v. a slide with a stop sign), subjects' responses
were significantly different based on whether they had been asked about a yield sign or not.
Altering people's responses based on questions that are misleading is known as the
misinformation effect.
There are two leading explanations for the misinformation effect. One is that the information in
post-event questions is accepted in place of what was actually seen; this is known as
misinformation acceptance. The second explanation is that people sometimes have difficulty
identifying the actual source of the memory being recalled (is it from what was seen or what was
asked?); this is known as source confusion.
Moreover, simply informing people that their memories may be influenced by post-event
information will not eliminate those influences. Indeed, cognitive psychologists, who one would
expect to be least likely to be susceptible to this memory distortion have been shown to be just as
vulnerable as anyone else. Vicente & Brewer (1993) surveyed some cognitive psychologists for
their knowledge of a well known study by deGroot (1965) that showed grandmaster chess players
had superior memory for chess pieces on a chess board with just a brief glance at the board than
novice players, which the cognitive psychologists were able to recall as deGroot's main finding.
However, these cognitive psychologists recalled that deGroot also had a condition in which chess
pieces were put on the board in random order, which resulted in no difference in recall between
the grandmasters and the novices, which would rule out general memory superiority as an
explanation of the results. But deGroot did not have that condition. In their partial defense, a well
known replication of deGroot's work by Chase and Simon (1973) did include that control condition.
Flashbulb Memories
Perhaps you are thinking that "there are some memories that I have that I will never forget. I
remember them as if they just happened. Sure, some of my memories may be become altered or
even distorted, but surely these special memories are not subject to such changes." What you are
thinking of are called flashblub memories, which are memories formed when some personally
significant event occurs, and the whole scene is encoded into memory. Examples of flashbulb
memories may include the first time someone asked you, or you asked someone, out on a date,
the first time you heard that a special person died, when you first heard you won a prize or
contest.
The way to try to study flashbulb memories to examine people's shared experiences. That is, what
they were doing when they first heard about a culturally significant event. In the US, for a slightly
older generation than us, the prime example has been the first time a person heard that John F.
Kennedy was shot and killed. A Canadian example might be when they heard about Paul
Henderson scoring the series winning goal against the USSR in 1972. More recent examples are
the Challenger space shuttle explosion, and Princess Diana's death. Do you remember where you
were when you first heard about those events?
Neisser and Harsch (1992) had subjects describe what was going on when they first heard about
the Challenger shuttle explosion. Two and half years later, Neisser and Harsch found their
subjects, and again asked them to describe what they had been doing when they first heard about
the Challenger explosion. They compared the descriptions and scored them for similarity. The
mean score was 2.95 out of 7. Three subjects of 44 got a perfect 7, and over half were less than
2.
In a journal article, Ulric Neisser, a cognitive psychologist, recalled that he first heard about the
attack on Pearl Harbour was during a baseball game broadcast. However, the Pearl Harbour
attack occurred on Dec 7, 1941, and no baseball games have ever been played in Dec (or even
Nov), so Neisser couldn't have been listening to a baseball game. There was a sports game being
broadcast on that day, but it was a football game. Those football teams had nicknames that
present day baseball teams have. Neisser presumably remembered the team nicknames, which
led him to assume that he had been listening to a baseball game, and never thought about the
date of the event.
This highlights an important point that the confidence that a person has in their memory is a poor
indicator of the accuracy of that memory. Clearly, Neisser was confident that his memory of first
hearing about the Pearl Harbour attack was during a baseball game, or he wouldn't have included
it in a journal article. Yet, the memory is clearly erroneous. The Challenger shuttle study also
found little relationship between confidence in a memory and the accuracy of that memory.
Notice that above I said erroneous, not false. I'm not sure that there are false memories exactly.
For example, if one of you 2 years from now recalled that I was an unkind person, and another of
you recalled that I was a kind person, I wouldn't say that either of you had a false memory of me.
You would just have that particular memory of me. However, if one of you recall 2 years from now
that I had bright red hair, that would be erroneous, because I didn't (don't). But again, I don't think
that I would call the memory false, because that's just what you recall.
I'm suggesting that memories don't have a truth value. Memories may or may not be consistent
with facts about the world, but I'm not sure that I would call that consistency truth (or inconsistency
falsehood).
Repressed & Recovered Memories
In recent years there has been much discussion of repressed memories. Repressed memories
are typically those involving some very traumatic event that the person does not want to
remember, so the memory is repressed, or pushed out of awareness. The memory is only
'recovered' when the person is fit for dealing with the subject of the memory. The recovered
memory is said to be unaltered.
If memory is reconstructive, and, thus, subject to alteration, then how are we to evaluate just
recovered repressed memories? Cautiously. It seems unlikely that a recovered memory (or
unrepressed memory) will be recalled perfectly. This is especially true when the memory has been
recalled by doing "memory work" with the help of a therapist. Such work typically involves some
suggestion of what happened earlier in the person's life, and the person may mistakenly believe
that this material are real memories.
As stated earlier, if someone remembers an incident in a particular way, that does not imply that
the event occurred in that particular way, or even that the event occurred at all. The confidence
that a person has in that memory is not sufficient to substantiate the claim that the memory is
correct.
Elizabeth Loftus has done studies to examine the issue of recovered memories (see Scientific
American, Sept. 1997). She has asked people about being lost in a mall when they were 5 years
old (an event that Loftus knows did not occur based on interviews with other family members).
Loftus found that 68% of participants reported true events from that age, and 25% of them
reported the false event (being lost in the mall). In another study, she made the suggestion to
participants that they had spilled a punch bowl on some people when they had attended a
wedding as a young child. In that study, 0% of participants recalled spilling the punch bowl in their
first interview, but in the 2nd interview 18% recalled the event, and 25% recalled the event in the
3rd interview.
Finally, Loftus addressed the issue of confidence in recollections in another study. People are
often confident about their memories, which is one of the reasons that recovered memories are
very powerful. People really believe that the events in question occurred, and the events are often
very negative, so we assume that they would not be lying about them. But does confidence predict
accuracy? Loftus had participants rate the likelihood that they had done 40 typical childhood
events. After 2 weeks, participants imagined each of the 40 events occurring in their childhood.
Then 2 weeks later, people rated the events again, and their ratings were higher. That is, they
rated the events as more likely (or were more confident) to have happened in their lives. This
illustrates imagination inflation, which is that confidence ratings increase when an event has been
imagined.
Loftus makes 3 suggestions as to why there are 'false' memories.
1. social demand to remember - people may feel pressured from the social situation to remember an
event, so they may say they remember the event even though they are not sure they do
2. memory construction via imagination - imagining an event may lead people to believe that the event
actually happened
3. not encouraging critical thinking about memory - if people's memories are simply accepted as
reported, then the people are not likely to consider the possibility that the event did not occur (if
Neisser had been encouraged to think about when Pearl Harbor actually happened (Dec 7, 1941),
then it's unlikely that he would have claimed to have been listening to a baseball game).
MEMORY & AGING
Normal aging
There is a great deal of discussion of aging effects on memory. The general stereotype is that as
you age, your memory becomes worse. Like all stereotypes, this is generally false, although
perhaps not entirely false. Here is the evidence.
As with the discussion we had regarding retrieval failure, whether there is a memory difference
attributable to age seems to depend on the memory task. Early research (1960s & early '70s)
found that older folks had difficulty on free recall tasks, but not recognition tasks. Thus, the
conclusion was age related memory deficits were a retrieval problem, as older folks did fine when
there when they had some retrieval cues (recognition) but not when they didn't (free recall).
Consistent with this is an age difference found for tip of the tongue experiences, which occur when
you can almost retrieval the word you're searching memory for, but not quite. Often people when
in this state can identify the first letter of the word and other information about it, such as the
number of syllables it has, but they just can't quite retrieve it. Older people tend to have more tip of
the tongue experiences than younger people, and there are similar findings for picture naming and
name finding tasks.
However, not all research on aging and memory has examined retrieval processing. In the 1970
and early '80s, researchers examined encoding processes, which was partly due to the levels of
processing theory that had suggested differences in memory performance are primarily a result of
encoding. Dual tasks reduce performance of older people relative to younger people more when
the dual task occurs at the time of encoding than at the time of retrieval. Furthermore, there is
evidence from PET (positron emission tomography, a means of analysing brain processing)
studies showing greater differences between older and younger people when they are encoding
information than when they are retrieving information.
Considering memory from the modal model perspective, studies have shown no age differences
for STM digit span (how many digits can someone repeat without making an error). However, that
is a fairly passive task, as the digits are simply given to the participant, and then the participant
has to repeat them back immediately, without processing them further. When greater processing
is required, age related memory differences appear. That is, when working memory is involved,
then age differences occur. This will be discussed further shortly.
Within LTM, older people seem to have greater difficulty when processing episodic memories than
younger people. The key factor seems to be the amount of deliberative, or intentional, processing.
When more deliberative, or intentional, processing is needed, either at encoding or retrieval, there
are greater memory differences between old and young people. Episodic retrieval requires the
retrieval of some contextual information. However, older people seem to encode less contextual
information than young people; for example, older people are less likely to identify if a word was
presented in CAPITAL or lower case letters, spoken by a man or woman, what colour it was
presented in, etc. Also, there seems to be a difference in reality monitoring (distinguishing the
source of information) between old and young people.
The ecological validity of some aging and memory studies has been questioned, as younger
adults may be more familiar with lab tasks, so the results may not transfer to everyday, nonlaboratory, situations. Memory research on more ecological tasks has shown that memory decline
is directly related to the length of the retention interval. Thus, memories that are 5 years old are
more accurate than memories that at 10 years old, than 20 years old, etc. Thus, older adults
would tend to have less accurate memories of their early lives than younger adults, but this
difference is simply due to the length of the retention interval, rather than the age of the
individuals.
Still within LTM, there seems to be little difference in semantic memory between older and
younger adults. Furthermore, there is also little, if any, difference in procedural (implicit) memory.
Thus, in these respects, people do not suffer memory deficits as a result of aging. However, in
both cases there can be a difference in speed, as older adults tend to perform tasks slower than
younger adults (even when the accuracy is the same).
Some researchers examined memory and aging from the perspective of resources, in an effort to
identify whether older and younger people have different amounts of processing resources
available to them. The methodology here is to identify a type of resource and measure it, and
relate that measurement to a measure of memory performance. Deliberative processing,
mentioned above, would seem to be an ideal candidate for such a resource. However, there is no
good measure of deliberative processing. There are good measures of two other resources.
These are working memory, and perceptual speed. Working memory we've discussed before.
Perceptual speed is the ability to perform simple perceptual-motor tasks, such as comparing two
stimuli (A - B). When these resources have been measured, they have been found to statistically
account for a great deal of the difference between young and old people in memory performance.
Perceptual speed actually gives a better account of that difference than working memory.
In summary, there do seem to be some memory differences as people age, but these differences
are restricted to active short term memory (i.e., working memory) and the use of episodic
memories. Also, the differences seem to be attributable to simple cognitive abilities, such as
working memory and perceptual speed.
Abnormal aging: Alzheimer's
This is the memory disorder that you have all heard about. Although widely talked about, only 5%
of people over the age of 70 have Alzheimer's, although that rises to 35% over the age of 85. In
1907, Alois Alzheimer doing an autopsy on a woman suffering with what we would call dementia
identified that she had abnormalities in her brain.
Those abnormalities in the neural tissue of the brain are the characteristic signs of Alzheimer's.
The affected neurons are in both the hippocampus, which is part of the limbic system and in part
functions as the focal point where processes leading to memory storage and retrieval begin, and
the cortex, which is used in forming associations between ideas and memories.
An MRI (magnetic resonance imaging) scan can identify Alzheimer's, but a certain diagnosis
cannot be made until after the person has died and an autopsy has been performed. Autopsy
should reveal the neurochemical changes in the brain that are indicative of Alzheimer's.
Characteristic neural tissue damage from Alzheimer's is that the cell bodies have shriveled protein
fliaments, and their dendrites also deteriorate. Specifically, there are plaques on the beta amyloid
protein and tangles of the tau protein.
Several causes for Alzheimer's are suspected, such as
 a slow acting virus
 toxic substances (e.g., aluminum in non-natural sources)
 oxidation by free radicals (oxygen ions in the body that seek to bond with another molecule to come into
balance, so they will steal particles from already balanced molecules - such as those that make up the nerve
cells), which has been suggested as the general cause of deterioration in the aging process; thus, antioxidants (e.g., vitamin E, vitamin C), which would bond with the free radicals, may help to lessen or even
prevent excessive oxidation
 too little acetylcholine (Ach; a neurotransmitter) being produced, so one approach could be to limit the
substances that use it up
 blood flow may be reduced in the brains of people with Alzheimer's; the amino acid (protein)
homocystain is known to be harmful to nerve cells and is also a risk factor for heart disease and high blood
pressure; homocystain can be reduced by folic acid and vitamin B12, and the levels of folic acid and vitamin
B12 have been found to be below the population mean for Alzheimer's patients, although still in the normal
range; thus, it's possible that using folic acid and vitamin B12 may help people with Alzheimer's; however,
the homocystain, folic acid and B12 levels may simply be an effect of some other cause rather than the
primary cause themselves
Some have suggested that nerve growth factor (NGO) may be used to improve the brains of
people with Alzheimer's (and other brain disorders such as cystic fibrosis, and damage due to
strokes). NGO has been shown to prevent brain deterioration in rats, but the administration of it
was directly into the brain; it's impossible to stick a needle directly into a human's brain, because
the human skull is too thick. Futhermore, NGO is too large a molecule to pass through the bloodbrain barrier (blood flows into the brain through one particular spot, and at that spot there is a sort
of a filter, so molecules that are bigger than the gaps in the filter cannot pass through). How to get
NGO into the brain? A possibility is to use nose drops. There are several cranial nerves that go
straight to the brain, and one of them gets information from the nose. If NGO could be passed
along that nerve, it would bypass the blood-brain barrier and get into the brain. Studies is currently
being done to see if this will be effective.
Finally, another suggestion is that Alzheimer's may be a syndrome, which would be a number of
different illnesses that all have effects that appear to be similar, rather than one disorder. What we
now call Alzheimer's could be a collection of different maladies that are not presently
distinguishable, so there could be several causes that produce the same resulting brain damage.
The risk factors for Alzheimer's are
 age, the older a person is the more likely the person will suffer Alzheimer's, and
 genetics, as Alzheimer's has been shown to have a genetic component in some cases, and
 being female, as woman are more likely to suffer Alzheimer's than men.
Also, Alzheimer's has been linked to having a particular protein, and the incidence of that protein varies
across the human population; Finns have more of this protein than other ethnic groups. As well, the
incidence of Alzheimer's generally increases the further away from the equator the population. Some people
have suggested that suffering a head injury early in life increases the risk of developing Alzheimer's later in
life, but the evidence is mixed for that proposition.
It appears that the more education one has the less likely one will develop Alzheimer's. However,
it's not clear what that result implies. It could simply be that using one's brain for more cognitive
(more as in a greater variety and a greater number) activities, as presumably people who have
gotten more education would do, will stave off the development of Alzheimer's. A variation on the
old "use it or lose it" adage.
Alzheimer's is degenerative, so once the damage begins it will continue until the person dies.
There is no cure, although some of the research outlined above is suggesting methods that might
be useful in reducing or perhaps even preventing the disorder. Diagnosis is done by asking the
individual a series of questions to test their short term memory. Also, Alzheimer's can be
diagnosed by ruling out other possible causal explanations for a memory deficit, such as a tumor,
or stroke. Still, diagnoisis is only about 90% accurate. The only way to know that a person has
Alzheimer's for sure is to do an autopsy after the person dies. Thus, the diagnosis when the
person is alive is "dementia of the Alzheimer's type," rather than "Alzheimer's." If the diagnosis
can be made, then Alzheimer's is already very far along. Once the such a diagnosis has been
made, the person generally lives another 3-9 years.
http://www.uwinnipeg.ca/~epritch1/alz2000.htm