MEMORY.pptx

MEMORY
 It is the encoding ,storage and retrieval of what was
learned earlier.

STAGES OF MEMORY
 Sensory memory
 Short term memory
 Long term memory

SENSORY MEMORY /REGISTER
 It refers to the brief storage of sensory information.
It is a buffer that lasts only briefly and unless it is
attended to and passed on for more processing, is
forgotten.
 Visual sensory register ( iconic memory ) holds
information for 1 second.[Sperling]
 Auditory (hearing) register holds information
somewhat longer i.e 4-5 seconds

 Studies with the visual sensory register have shown
that it can hold atleast 11 to 16 items before it loses
the information through decay.

SHORT TERM MEMORY
 It is the memory that holds information received
from the sensory register for upto about 30 seconds
,although the length of retention depends on a
number of factors.
 In addition to it’s transient nature ,it also has very
limited storage capacity.
 The capacity is estimated about 7 items plus or
minus 2

CHUNKING
 The storage capacity of short term memory can be
raised by a process called CHUNKING.
 Most of us have learned to combine several items
into a chunk as we receive them; then we can
retain several (7 plus minus 2) of these chunks in
our short term memories.

FATE OF SHORT TERM MEMORY
 Much of the information is lost.
 Some of the information can be retrieved and used
before it is lost.
 Some of the information is passed along to the next
memory stage – long term memory-through
rehearsal.

REHEARSAL
 The process of rehearsal consists of keeping items
of information in the centre of attention perhaps by
repeating them silently or aloud.
 The amount of rehearsal given to items is important
in the transfer of information from short term to long
term memory.

LONG TERM MEMORY
 The time span over which information can be stored
in long term memory cannot be stated very
precisely .Long term memories may last for years
,months ,days or even a lifetime.

Long term
memory
Explicit
memory /
Declarative
memory
Implicit/Non
declarative
memory

TYPES OF LONG TERM MEMORY-EXPLICIT
MEMORY
 It refers to knowledge or experiences that can be
conciously remembered.
 There are two types of explicit memory:-
1.Episodic memory-It refers to the firsthand
experiences that we have had. Eg.recollections of
high school graduation day or the fantastic dinner
we had on New Year’s Eve.
2.Semantic memory-It refers to the firsthand
knowledge of facts and concepts about the world.
Eg.that India got independence in 1947 and that
one definition of the word affect is the experience of
feeling or emotion.

Explicit
memory
Episodic
memory
Semantic
memory

WHAT ARE THE MEASURES TO ASSESS
EXPLICIT MEMORY?
 1.RECALL
 2 .RECOGNITION
 3.RELEARNING

RECALL
 A recall memory test is a measure of explicit
memory that involves bringing from memory
information that has previously been remembered.
We rely on our recall memory when we take an
essay test because it requires us to generate
previously remembered information.
 It can be tested by unaided recall of previously
studied material ( free recall) or by presenting a cue
for the material to be remembered ( cued recall).
 To detect the sensitivity of memory impairment, free
recall is most sensitive.

RECOGNITION
A recognition memory test is a measure of explicit
memory that involves determining whether the
information has been seen or learned before.
It involves two steps-
 1.Generating an answer
 2. Determining whether it seems to be the correct
one.
Recognition as on multiple choice test ,only involves
determining which item from a list seems most
correct.

RELEARNING
 Measures of relearning assess how much more
quickly information is processed or learned when it
is studied again after it has already been learned
but then forgotten.

IMPLICIT MEMORY
 It refers to the influence of experience on behavior,
even if the individual is not aware of those
influences.
 It is of 3 types-
1.Procedural memory
2.Classical conditioning effects
3.Priming

TYPES OF IMPLICIT MEMORY
Procedural memory
Classical conditioning
effects
Priming

PROCEDURAL MEMORY
 It refers to our often unexplainable knowledge of
how to do things
 It allows us to perform complex tasks even though
we may not be able to explain others how we do
them.
 Eg. There is no way to tell someone how to ride a
bicycle ; a person has to learn by doing it.

CLASSICAL CONDITIONING EFFECTS
 In this type of implicit memory ,we learn ,often
without effort or awareness to associate neutral
stimuli ( such as sound or light) with another
stimulus (such as food ) which creates a naturally
occurring response such as enjoyment or
salivation. The memory for the association is
demonstrated when the conditioned stimulus (the
sound) begins to create the same response as the
unconditioned stimulus (the food) did before
learning

PRIMING
 It implies changes in behavior as a result of
experiences that have happened frequently or
recently .It refers to both the activation of
knowledge ( eg. we can prime the concept of
kindness by presenting people with words related to
kindness) and to the influence of that activation on
behavior ( people who are primed with the concept
of kindness may act more kindly).

TEST TO MEASURE THE INFLUENCE OF
PRIMING ON MEMORY- WORD FRAGMENT
TEST
 Try to complete the following word fragments but
work on each for only 3-4 seconds
 _ib_a_y
 _h_s_ _ i_n
 _o_k
 _h_is _

 Now read the following sentence carefully:-
He got his materials from the shelves, checked them
out and then left the building.

 1 and 3 library and book- because the concept of
library and book were primed even though they
were not mentioned explicitly.
 2 and 4 Physician and chase

ENCODING AND STORING LONG TERM
MEMORIES
 Encoding is a process that controls movement from
working to long term memory store.
 The importance of encoding in long term memory is
highlighted by encoding failures.
 Although we have seen a rupee coin/penny countless
times, most of us do not have an accurate long term
memory image of what is on the head side of rupee
coin.
 In one study of penny recognition, less than half of the
people in the study chose the right coin.
 Encoding for long term storage requires special
attention or strategies of some sort, just being exposed
to something is usually not sufficient for long term
memory storage.

THE ROLE OF ORGANIZATION
 One strategy to remember things well is to organize or
arrange the input so that it fits into existing long term
memory categories ,is grouped in some logical manner
or is arranged in some other way that makes sense.
 The things we learn are usually are not inherently well
organized.
 We must do our own organizational encoding of
incoming information known as subjective organization.
 People tend to recall pairs of words and short strings of
words together better.
 Such groupings or subjective organizations lead to
better memory

THE ROLE OF IMAGERY
 The organization and meaning given to verbal
information is ,as we have seen, quite influential in
promoting long term retention.
 Another factor is whether the incoming information
is stored by forming images of it.
 In case of visual images, the picture in the head is
not an exact copy of the input, is not complete and
parts of it are emphasized while others are absent.
 Images are thus partial and altered representations.

THE ROLE OF IMAGERY
 The words for which visual images are easily
formed are termed as concrete while those that
evoke very little visual imagery are termed abstract.
 E.g. desk is concrete
mercy is abstract

EXPERIMENT TO CHECK THE ROLE OF
IMAGERY IN ENCODING
 Paired associate technique –The first element of
the pair is called the stimulus and the second
element is called the response.
 Given the stimulus ,you learn to make the response
that has been paired with it.
 Having an item that evokes imagery ( concrete
word ) in the stimulus position resulted in good
recall.

THE ROLE OF CONSTRUCTIVE
PROCESSES
 During encoding, the to-be-remembered
information ,especially if it is a complex life event or
something that you have read ,is modified .Certain
details are accentuated , the material may be
simplified or it may be changed in many other ways
so that what is encoded and stored is far from literal
copy of the input. These modifications are called
constructive processes.
 E.g. Suppose you read ‘ The driver of the car was
seen drinking before he was involved in an
accident’. We would probably infer that drinking
caused the accident and remember the sentence
as stating causation, although it does not.

RETRIEVAL FROM LONG TERM
MEMORY
 Information is encoded and stored in long term
memory but it must be retrieved , if it is to be used.
 Retrieval cues- Finding information from long term
memory store is aided be retrieval cues or
reminders which direct the memory search to the
appropriate part of long term memory library.
 Retrieval is good when conditions favour rich and
elaborate encoding.

RECONSTRUCTIVE PROCESSES IN
RETRIEVAL
 Reconstructive processes are modifications of
already stored input.
 The distinction between constructive and
reconstructive processes is however blurred; it may
be difficult to tell whether the modifications in
memory occurred in encoding stage or later.
 Reconstruction is sometimes called confabulation in
case of people with memory disorders who
remember very little and try to fill in the memory
gaps during retrieval.
 Reconstructive processes are often seen in the
answers to leading questions that bias the retrieval
of what was stored.

QUESTIONS
 Group 1-How fast were the cars going when they
hit into each other?
 Group 2-How fast were the cars going when they
smashed into each other?
one week later
Both groups were asked –Did you see any broken
glass?

WHY DO WE FORGET?
 Forgetting refers to the apparent loss of information
already encoded and stored in long term memory.
 Much of what we think we have forgotten does not
really qualify as forgotten as it was never encoded
and stored in the first place.
 Some information , due to lack of attention , may
not have reached short term memory from the
sensory register, or due to inadequate coding and
rehearsal ,may not have been passed from short
term to long term memory.

INTERFERENCE THEORIES
 Memories interfering with memories.
 Forgetting is not just caused by the passage of time
but caused by one memory competing with or
replacing other memory.

Types of
interference
Retroactive
interference
Proactive
interference

RETROACTIVE INTERFERENCE
 When a new memory interferes with remembering
old information.
 E.g. When new phone number interferes with ability
to remember old phone number.

PROACTIVE INTERFERENCE
 Opposite of retroactive interference
 When an old memory interferes with remembering
new information.
 E.g Memories of where you parked your car in the
campus interferes with ability to find the car today.

MOTIVATED FORGETTING
 Undesired memory is held back from awareness.
1. Suppression- concious forgetting
2. Repression – unconcious forgetting

DECAY THEORIES
 Memories fade away or decay gradually if unused
 Time plays a critical role
 Ability to retrieve declines with time.
 Biology based theory
 When new memory is formed, it creates a memory
trace i.e a change in brain structure or chemistry.
 If unused , normal brain metabolic processes erode
memory trace.
 Not widely favored today.

BIOLOGY OF MEMORY
 The effective clinician needs to understand
something of the biology of memory, the varieties of
memory dysfunction and how memory can be
evaluated.

FROM SYNAPSES TO MEMORY
 Memory is a particular case of the general biologic
phenomenon of neural plasticity.
 Neurons can show history dependent activity by
responding differently as a function of prior input,
and this plasticity of nerve cells and synapses is the
basis for memory.

PLASTICITY
 Neurobiologic evidence supports two necessary
conclusions
 short lasting plasticity which may last for seconds
or minutes depending on specific synaptic events
including an increase in neurotransmitter release.
 long lasting memory which depends on new
protein synthesis , the physical growth of neural
processes and increase in number of synaptic
connections.

STUDY OF APLYSIA CALIFORNICA
 Individual neurons and the connections between
neurons of Aplysia have been identified.
 Aplysia is capable of associative learning (
including classical conditioning and operant
conditiong ) and nonassociative learning (
habiuation and sensitization).
 Sensitization had been studied using gill withdrawl
reflex , a defensive reaction in which tactile
stimulation causes the gill and siphon to retract.
 When tactile stimulation is preceded by sensory
stimulation, to the head or tail, gill withdrawl is
facilitated.

 The cellular changes underlying this sensitization begins
when a sensory neuron activates a modulatory
interneuron , enhancing the strength of synapses within
the circuitry responsible for reflex . This modulation
depends on a second messenger system in which
intracellular molecules lead to enhanced
neurotransmitter release that lasts for minutes in the
reflex pathway.
 Both short and long lasting changes are associated with
enhanced neurotransmitter release.
 Long lasting change usually requires expression of
genes and synthesis of new proteins.
 Also long lasting changes are accompanied by growth of
neural processes of neurons within the reflex circuit.

 In vertebrates , memory cannot be directly studied
as in Aplysia .
 Nevertheless , it is known that behavioral
manipulations result in change in brain architecture.

LONG TERM POTENTIATION
 This phenomenon is a candidate mechanism of long
term memory.
 It is observed when a post synaptic neuron is
persistently depolarized after a high frequency burst of
presynaptic neural firing.
 It is established quickly and then lasts for a long time.
 It occurs only at potentiated synapses.
 It occurs primarily in the hippocampus.
 Involves activation of NMDA receptor ,which permits
influx of calcium into postsynaptic cell.
 It is maintained by an increase in the number of alpha -
amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA
, non NMDA) receptors and also possibly by increased
neurotransmitter release.

ASSOCIATIVE LEARNING
 Study of classical conditioning has provided insight to
the biology of memory.
 Studied well in rabbits using an airpuff into the eye as an
unconditioned stimulus and tone as conditioned
stimulus.
 After repeated pairings, tone alone elicits an eye blink.
 Reversible lesions of deep nuclei of cerebellum
eliminate conditioned response.
 It has been suggested that synaptic changes in
cerebellar cortex are critical for learned timing .
 In contrast ,synaptic changes in the deep nuclei are
critical for forming association between conditioned and
unconditioned stimulus.

CORTICAL ORGANIZATION OF
MEMORY
 1920 , Karl Lashley experimented on rats by
removing different amount of cerebral cortex .
 Number of trials needed to relearn a maze problem
before and after surgery was noted.
 Deficit was proportional to the amount of cortex
removed.

FUNCTIONAL ORGANIZATION OF
MAMMALIAN CORTEX
 Nearly one half of primate neocortex is specialized for
visual functions.
 Specific visual processing areas in the dorsal and
ventral streams ,together with areas in the prefrontal
cortex ,register the immediate experience of perceptual
processing.
 Electrophysiologic studies show that neurons in the area
TE , which is one part of inferotemporal cortex , register
specific and complex features of visual stimuli such as
shape and respond selectively to patterns and objects.
 Regions of visual cortex in forward portions of dorsal
and ventral streams serve as ultimate repositories of
visual memories.

 In sum, memory is distributed and localized in
cerebral cortex.
 It is distributed in the sense that there is no cortical
center dedicated solely to the storage of memories.
 It is localized in the sense that different aspects or
dimensions or events are stored at specific cortical
sites.

MEMORY SYSTEMS
 Declarative memory depends upon medial temporal
and midline diencephalic structures alongwith large
portions of the neocortex.
 Frontal lobes are fundamentally crucial for
declarative memory .
 Patients with frontal lesions have a poor memory
for the context in which information was acquired
,they have difficulty in unaided recall , and they may
even have some mild difficulty on tests for
recognition.

NEUROIMAGING AND MEMORY
 Activation of posterior prefrontal regions with PET and f
MRI have shown that these regions are involved in
strategic processing during retrieval and working
memory.
 Anterior frontal regions near the frontal poles have been
linked with functioning such as evaluating the products
of retrieval.
 Frontal connections with posterior neocortical regions
support the organization of retrieval and manipulation of
information in working memory.
 Multiple parietal regions ( including superior and inferior
parietal lobules , precuneus ,posterior cingulate and
retrosplenial cortex ) are activated in conjunction with
remembering recent experiences.

 Hippocampus appears to be involved in the
recollection of recent events.
 Left inferior prefrontal cortex is engaged as a result
of attempts to encode a word , hippocampal activity
at encoding is more closely related with whether
coding leads to a stable memory that can later be
retrieved.

SLEEP AND MEMORY
 Frued noted that dreams could reveal fragments of recent
experiences in the form of day residues.
 Recent experiments have provided new empirical support to
holster the idea that memory processing during sleep serves
an adaptive function.
 Memory performance can ve facilitated when sleep occurs
after initial learning.
 Memory storage appears to be aided explicitly by processing
during deep sleep within a few hours after learning, especially
in stage 3 and 4 ( slow wave sleep).
 Slow wave sleep facilitates the storage of declarative but not
nondeclarative memories.
 Neuronal recordings in animals have revealed a phenomenon
of hippocampal replay in which activity patterns expressed
during the day are later observed during sleep.

AMNESIA
 A loss of new learning ability that extends across
all sensory modalities and stimulus domains is
anterograde amnesia and can be explained by
understanding the role of brain structures critical for
acquiring information about facts and events.
 Retrograde amnesia is a loss of knowledge
acquired before the onset of amnesia. Typically,
anterograde amnesia occurs with retrograde
amnesia.
 Retrograde deficits have a temporal gradient,
following a principle known as Ribot’s law. Deficits
more severe for information that was recently
learned.

SPECIALIZED MEMORY FUNCTION
 Amnesia can result from damage to the medical
portion of temporal lobe or damage to regions of
midline diencephelon.
 Medial temporal lobe structures include
hippocampus including the dentate gyrus,
hippocampal fields CA1, CA 2,CA3 and the
subiculum – and the adjacent cortical regions
including the entorhinal, perirhinal and
parahippocampal cortices.

STUDIES OF HM
 HM was a severely amnesic patient.
 He sustained bilateral resection of medical temporal
lobe to relieve severe epilepsy.
 Seizure condition improved after surgery .
 But he experienced profound forgetfullness.
 Intellectual functions were generally preserved.
 Exhibited normal immediate memory.
 But could not remember what had recently occured
after an interruption.
 Felt as he were waking from a dream as he had no
recollection of what just happened.

MEMORY IMPAIRMENT OF EP
 72 yrs old, Was diagnosed with herpes simplex
encephalitis.
 Medial temporal lobe region damaged.
 During testing sessions, cordial and talked freely
about life experiences.
 But relied exclusively on stories of childhood and
early adulthood.
 Tests involving facts about his life and
autobiographical experiences revealed poor
memory for the time leading up to his illness but
normal memory for his childhood.

 From these experiments, it is noteworthy that the
impairment selectively concerns memory for
selective knowledge and autobiographical events,
collectively termed as declarative memory.
 Such studies indicate that damage to hippocampal
structures result in clinically significant memory
impairment.

 Memory impairment due to medial temporal lobe
damage is also typical in patients with early
Alzheimer’s disease or amnesia mild cognitive
impairment.
 As Alzheimer’s disease progresses, the pathology
affects many cortical regions and produces
substantial cognitive deficits and memory
dysfunction.

ALCOHOLIC KORSAKOFF SYNDROME
 It is the most prevelant and best studied example of
diencephalic amnesia.
 Damage is found in the regions of brain that may be
especially sensitive to prolonged bouts of thiamine
deficiency and alcohol abuse.
 The critical structures damaged in diencephalic
amnesia include mammillary nuclei in the
hypothalamus, the dorsomedial nucleus of the
thalamus, the anterior nucleus, the internal
medullary lamina and the mammillothalamic tract.

 Patients with Korsakoff syndrome typically exhibit
memory impairment due to combination of
diencephalic damage and frontal lobe pathology.
 Frontal damage alone produces characteristic
cognitive defects and specific memory problems. (
e.g. in effortful retrieval and evaluation.
 There is both retrograde and anterograde amnesia
characterized by confabulation.

RETROGRADE AMNESIA
Memory loss typically affects recent memories more
than remote memories.
Memories are dynamic
As time passes, some memories are forgotten
whereas others become stronger due to process of
consolidation that depends upon cortical, medial
temporal and diencephalic structures.
An event is experienced and encoded by a collection
of cortical regions involved in representing a
combination of different event features.
At the same time, hippocampus and adjacent cortex
receive pertinent high level information from all
sensory modalities.

 Later when the original event is recalled, the same set of
cortical regions is activated.
 If a subset of cortical regions is activated, the
hippocampus and related structures can facilitate recall
by facilitating the remaining cortical structures.
 When the original event is retrieved and newly
associated with other information, hippocampal cortical
networks can be modified.
 In this way, a gradual consolidation process occurs that
changes memory storage.
 The neocortical components representing some events
can become so effectively linked together that ultimately
a memory can be retrieved without any contribution from
medial temporal lobe.
 As a result, amnesic patients can exhibit normal retrieval
of remote facts and autobiographical memories.

 Patients with focal retrograde amnesia exhibit
substantial retrograde memory impairment with only
moderately impaired new learning ability. Some
capacity for new learning remains, presumably
because medial temporal lobe structures can
communicate with other areas of cortex that remain
undamaged.

ASSESSMENT OF MEMORY
FUNCTIONS
 A complete assessment of memory usually involves
several specialized tests that sample intellectual
functions , new learning capacity, remote memory
and memory self report.

ASSESSMENT OF GENERAL
INTELLECTUAL FUNCTIONS
 It is central to any neurophychological examination.
 Information about intellectual functions provides
information about a patient’s general test taking
ability and a way to assess the selectivity of
memory impairment.
 Useful tests include the Wechsler Adult Intelligence
scale, a test for object naming such as Boston
Naming test, a rating scale to assess the possibility
of global dementia, a test of word fluency and
specialized tests of frontal lobe function.

NEW LEARNING CAPACITY( IMMEDIATE
AND RECENT MEMORY)
 Memory tests are sensitive to impaired new
learning capacity when they adhere to either of two
critical principles.
 1. Tests are sensitive to memory impairment when
more information is presented than that can be held
in immediate memory.
 2. Tests are sensitive to memory impairment when
a delay, filled with distraction, is interposed between
the learning phase and test phase.

 The specialization of function of two cerebral
hemispheres in humans means that left and right
unilateral damage is associated with different kinds
of memory problems.
 Different kinds of memory tests must be used when
unilateral damage is a possibility.
 Damage to medial temporal or diencephalic
structures in the right cerebral hemisphere impairs
memory for faces, spatial layouts, and other
nonverbal material that is typically encoded without
verbal labels.
 Left medial temporal lobe damage can lead to
impaired memory for spoken and written text.
 Right medial temporal lobe damage can lead to
impaired learning of spatial arrays, whether the
layouts are examined by vision or touch.

REMOTE MEMORY
 Most quantitative tests for remote memory are
composed of material in the public domain that can
be corroborated.
 E.g. Tests have been used that concern news
event, photographs of famous persons.
 Advantage – One can sample large number of
events and often target particular periods.
 Disadvantage- not useful for detecting memory loss
for information learned during weeks or months
immediately before onset of amnesia.

 Autobiographical memory tests can potentially
provide fine grained information about a patient’s
retrograde memory.
 In the word probe task, patients are asked to
recollect specific episodes from their past in
response to single word cues and date the
episodes.
 The number of episodes recalled tends to be
systematically related to the time the episode is
taken.
 Most memories naturally come from recent periods.
 In contrast, patients with amnesia often exhibit
temporally graded retrograde amnesia, drawing
relatively few episodes from recent past but
producing as many remote autobiographical
memories as normal subjects.

MEMORY SELF REPORTS
 Tests of ability to judge one’s memory are called tests of
metamemory.
 Self rating scales- yield qualitative and quantitative
information about memory impairment.
 As a result, it is possible to distinguish memory
complaints associated with depression from amnesia.
 Depressed patients tend to rate their memory as poor in
relatively undifferentiated way, endorsing equally all of
the items on a self rating form.
 Amnesic patients do not report difficulty in remembering
very remote memory events or in following what is being
said to them, but they do report having difficulty
remembering an event a few minutes after it happens.

PSYCHOGENIC AMNESIA
 Memory impairment differs markedly from typical
patterns of memory loss that follow brain damage.
 Some cases present with sudden onset of
retrograde amnesia, loss of personal identity and
minimal anterograde amnesia.
 Patients may even be unable to recall their name.
 Given the psychological forces that prompt the
onset of amnesia in these cases, commonly termed
as psychogenic amnesia, or sometimes hysterical
amnesia, functional amnesia or dissociative
amnesia.

INFANTILE AMNESIA
 The apparent absence of concious memory for
experiences from approx. first 3 years of life.
 Reason- capacity for declarative memory does not
become fully available until approximately third year of
life whereas non declarative memory emerges early in
infancy (e.g classical conditioning and skill learning)
 Thus, it results not from adult’s failure to retrieve early
memories, but from child’s failure to adequately store
them in first place.
 As neocortex develops, memories become more
complex, language abilities allow for more elaborate
verbal descriptions, and a developing sense of self
supports autobiographical knowledge.

 Declarative memories formed very early in life are
fragmentary, simple and tied to specific context of
an infant’s understanding of the world. They are
unlike typical declarative memories in adults, which
are imbued with meaning and a complex
understanding of events.

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