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Mechanisms of Memory
Memory as psychical function
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Memory function helps fixing of perceived information,
keeping it in verbal form or as traces of percept stimuli and
recognizing of this information in proper time. Genetic
memory keeps information about body structure and forms
of its behavior. Biological memory is presented in both
philogenetic and ontogenetic forms. The immune memory
and psychical memory for instance, belong to ontogenetic
memory.
General characteristics of memory are duration, strength of
keeping the information and exactness of its recognizing. In
man mechanisms of perception and keeping the information
are developed better, comparing to other mammalians.
According to duration is concerned short-time and long-time
memory; in relation to kind of information – sensory and
logic.
Nerve substrate of memory
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It’s discovered the nervous substrate of long-term
memory is mostly cerebral cortex. The most
important regions are temporal lobes, prefrontal area
and hippocampus. Experimental researches revealed
that some thalamic nuclei and reticular formation take
part in memory function.
Reticular formation gives ascending stimulatory
influences to cerebral cortex, which help in keeping
awake condition of cortex and provides voluntary
attention.
Levels of processing
Processing a word deeply—by its meaning (semantic
encoding)—produces better recognition of it at a later
time than does shallow processing by attending to its appearance
or sound.
Physiological mechanisms of memory
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At the molecular level, the habitation effect in the sensory
terminal results from progressive closure of calcium channels
through the presynaptic terminal membrane.
In case of facilitation, the molecular mechanism is believed to be
following. Facilitated synapse releases serotonin that activates
adenylyl cyclase in postsynaptic cell. Then cyclic AMP activates
proteinkinase that then causes phosphorylation of proteins. This
blocks potassium channels for minutes or even weeks. Lack of
potassium causes prolonged action potential in the presynaptic
terminal that leads to activation of calcium pores, allowing
tremendous quantities of calcium ions to enter the sensory
terminal. This causes greatly increased transmitter release,
thereby markedly facilitating synaptic transmission.
Thus in a very indirect way, the associative effect of stimulation
the facilitator neuron at the same time that the sensory neuron is
stimulated causes prolonged increase in excitatory sensitivity of
the sensory terminal, and this establishes the memory trace.
Sensory Memory
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Information first enters the memory system through
the senses. We register and briefly store visual images
via iconic memory and sounds via echoic memory.
As information enters the memory system through
our senses, we briefly register and store visual images
via iconic memory, in which picture images last no
more than a few tenths of a second. We register and
store sounds via echoic memory, where echoes of
auditory stimuli may linger as long as 3 or 4 seconds.
Working/Short-Term Memory
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At any given time, we can focus on and process only about
seven items of information (either new or retrieved from our
memory store). Without rehearsal, information disappears
from short-term memory within seconds. Our capacity for
storing information permanently in long-term memory is
essentially unlimited.
Our short-term memory span for information just presented is
limited—a seconds-long retention of up to about seven items,
depending on the information and how it is presented. Our
capacity for storing information permanently in long-term
memory is essentially unlimited.
Short term memory
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Eric Kandel showed initially that weaker stimuli give rise to a
form of short term memory, which lasts from minutes to
hours. The mechanism for this "short term memory" is that
particular ion channels are affected in such a manner that
more calcium ions will enter the nerve terminal.
This leads to an increased amount of transmitter release at the
synapse, and thereby to an amplification of the reflex. This
change is due to a phosphorylation of certain ion channel
proteins, that is utilizing the molecular mechanism described
by Paul Greengard.
Sperling’s classic experiments on the duration of visual
sensory memory simulate Iconic Memory. You will see nine
random letters flashed in a 3 x 3 matrix, and will attempt to
recall the letters under three conditions: free-recall, cuedrecall, and delayed cued-recall. Your results will be compared
to Sperling’s finding of rapid decay of the visual “icon.”
Short-term memory decay
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Unless
rehearsed,
verbal
information
may be quickly
forgotten.
Long-Term Memory
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Reticular formation gives ascending
stimulatory influences to cerebral cortex,
which help in keeping awake condition of
cortex and provides voluntary attention.
At the molecular level, the habitation effect in
the sensory terminal results from progressive
closure of calcium channels through the
presynaptic terminal membrane.
Storing Memories in the Brain
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Researchers are exploring memory-related changes within and
between single neurons. Long-term potentiation (LTP) appears
to be the neural basis of learning and memory. Stress triggers
hormonal changes that arouse brain areas and can produce
indelible memories. We are particularly likely to remember
vivid events that form flashbulb memories. We have two
memory systems.
Explicit (declarative) memories of general knowledge, facts,
and experiences are processed by the hippocampus. Implicit
(nondeclarative) memories of skills and conditioned responses
are processed by other parts of the brain, including the
cerebellum.
Thinking process as psychical function
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The prefrontal association area is essential to carrying out thought
processes in the mind. This presumably results from some of the
same capabilities of the prefrontal cortex that allow it to plan
motor activities.
The prefrontal association area is frequently described as
important for elaboration of thoughts to store on a short-term basis
“working memories” that are used to analyze each new thought
while it is entering the braine. The somatic, visual, and auditory
association areas all meet one another in the posterior part of the
superior temporal lobe. This area is especially highly developed in
the dominant side of the brain – the left side in almost all righthanded people.
It plays the greatest single role of any part of cerebral cortex in the
higher comprehensive levels of brain function that we call
intelligence. This zone is also called general interpretative area,
the gnostic area, the knowing area, tertiary association area. It is
best known as Wernike’s area in honor of the neurologist who
first describes it.
Long term memory
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A more powerful and long lasting stimulus will result in a
form of long term memory that can remain for weeks. The
stronger stimulus will give rise to increased levels of the
messenger molecule cAMP and thereby protein kinase A.
These signals will reach the cell nucleus and cause a change
in a number of proteins in the synapse. The formation of
certain proteins will increase, while others will decrease. The
final result is that the shape of the synapse can increase and
thereby create a long lasting increase of synaptic function.
In contrast to short term memory, long term memory
requires that new proteins are formed. If this synthesis of
new proteins is prevented, the long term memory will be
blocked but not the short term memory.
Studying Memory: InformationProcessing
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A model of how memory works can help us
think about how we form and retrieve
memories. One model that has often been used
is a computer’s informationprocessing system,
which is in some ways similar to human
memory.
To remember any event, we must get
information into our brain (encoding), retain
that information (storage), and later get it back
out (retrieval).
How we form memories
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1. We first record to-be-remembered
information as a fleeting sensory memory.
2. From there, we process information into a
short-term memory bin, where we encode it
through rehearsal.
3. Finally, information moves into long-term
memory for later retrieval.
Encoding: Getting Information In
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Some information, such as the route you
walked to your last class, you process with
great ease, freeing your memory system to
focus on less familiar events.
But to retain novel information, such as a
friend’s new cellphone number, you need to
pay attention and try hard.
Without conscious effort you automatically process
information about:
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• space. While studying, you often encode the place on a page
where certain material appears; later, when struggling to recall that
information, you may visualize its location.
• time. While going about your day, you unintentionally note the
sequence of the day’s events. Later, when you realize you’ve left
your coat somewhere, you can recreate that sequence and retrace
your steps.
• frequency. You effortlessly keep track of how many times things
happen, thus enabling you to realize “this is the third time I’ve run
into her today.”
• well-learned information. For example, when you see words in
your native language, perhaps on the side of a delivery truck, you
cannot help but register their meanings. At such times, automatic
processing is so effortless that it is difficult to shut it off.
Effortful Processing
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We encode and retain vast amounts of
information automatically, but we remember
other types of information, such as this
chapter’s concepts, only with effort and
attention. Effortful processing often produces
durable and accessible memories.
When learning novel information such as
names, we can boost our memory through
rehearsal, or conscious repetition.
How We Encode
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Some types of information, notably information
concerning space, time, and frequency, we encode
mostly automatically. Other types of information,
including much of our processing of meaning,
imagery, and organization, require effort.
Mnemonic devices depend on the memorability of
visual images and of information that is organized
into chunks. Organizing information into chunks and
hierarchies also aids memory.
What We Encode
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When processing verbal information for storage, we
usually encode its meaning, associating it with what
we already know or imagine. Whether we hear eyescreem as “ice cream” or “I scream” depends on how
the context and our experience guide us to interpret
and encode the sounds.
Visual encoding (of images) and acoustic encoding
(of sounds) engage shallower processing than
semantic encoding (of meaning). We process verbal
information best when we make it relevant to
ourselves (the self-reference effect).
Storage: Retaining Information
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When people develop expertise in an area, they
process information not only in chunks but
also in hierarchies composed of a few broad
concepts divided and subdivided into narrower
concepts and facts.
Organizing knowledge in hierarchies helps us
retrieve information efficiently.
Effects of chunking on memory
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When we
organize
information into
meaningful
units, such as
letters, words,
and phrases, we
recall it more
easily.
Organization benefits memory
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When we organize words or concepts into hierarchical groups,
as illustrated here with concepts in this chapter, we remember
them better than when we see them presented randomly.
Retrieval: Getting Information
Out
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Recall is the ability to retrieve information not in
conscious awareness; a fill-in-the-blank question tests
recall. Recognition is the ability to identify items
previously learned; a multiplechoice question tests
recognition. Relearning is the ability to master
previously stored information more quickly than you
originally learned it.
Retrieval cues catch our attention and tweak our web
of associations, helping to move target information
into conscious awareness. Priming is the process of
activating associations (often unconsciously).
Retrieval Cues
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To be remembered, information must be encoded,
stored, and then retrieved. Memory is recall,
recognition, and relearning. With the aid of
associations (cues) that prime the memory, we
retrieve the information we want to remember.
Cues sometimes come from returning to the original
context. We use our senses as cues-a taste, smell, or
sight may evoke us to recall a memory. Mood affects
memory, too. While in a good or bad mood, we tend
to retrieve memories congruent with that mood.
Forgetting
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We may fail to encode information for entry into our memory
system. Memories may fade after storage—rapidly at first, and
then leveling off, a trend known as the forgetting curve.
We may experience retrieval failure, when old and new
material compete, when we don’t have adequate retrieval cues,
or possibly, in rare instances, because of motivated forgetting,
or repression. In proactive interference, something learned in
the past interferes with our ability to recall something recently
learned. In retroactive interference, something recently learned
interferes with something learned in the past.
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Psychologists now tend to agree that:
(1) Abuse happens, and can leave lasting scars.
(2) Some innocent people have been falsely convicted of abuse
that never happened, and some true abusers have used the
controversy over recovered memories to avoid punishment.
(3) Forgetting isolated past events, good or bad, is an ordinary
part of life.
(4) Recovering good and bad memories, triggered by some
memory cue, is commonplace.
(5) Infantile amnesia—the inability to recall memories from the
first three years of life—makes recovery of very early childhood
memories unlikely.
(6) Memories obtained under the influence of hypnosis or drugs
or therapy are unreliable.
(7) Both real and false memories cause stress and suffering.
Three sins of forgetting
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Absent-mindedness—inattention to details leads to
encoding failure (our mind is elsewhere as we lay
down the car keys).
Transience—storage decay over time (after we part
ways with former classmates, unused information
fades).
Blocking—inaccessibility of stored information
(seeing an actor in an old movie, we feel the name on
the tip of our tongue but experience retrieval
failure—we cannot get it out).
Three sins of distortion
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Misattribution—confusing the source of information
(putting words in someone else’s mouth or
remembering a dream as an actual happening).
Suggestibility—the lingering effects of
misinformation (a leading question—“Did Mr. Jones
touch your private parts?”—later becomes a young
child’s false memory).
Bias—belief-colored recollections (current feelings
toward a friend may color our recalled initial
feelings).