Memory - For Physicians and Tests for memory - Short term, immediate, long term and remote memory. Semantic and Event memory.

1. MEMORYBy : Dr Chetan K
Ganteppanavar

2. Brain facts
 Alexander the Great was able to remember all of
the names of his soldiers—there were
approximately 30,000 people in his army. Similarly
were the Pandits of Vedic age who used to
remember all the Shlokas of Vedas and
Upanishads.
 Mozart was able to play and write down all of the
notes from a song he had heard.
 Short-term memory can hold, on average, 7
things at a time. If you need to remember more
than that, write it down and most phone
numbers are 7 digits

3. Anatomy Of Brain Memory

4. Structures involved are :
 Subcortical Structures
1. Hippocampus
2. Cerebellum
3. Amygdala
4. Basal Ganglia and motor memory
 Cortical Structures
1. Frontal lobe
2. Parietal Lobe
3. Temporal lobe
4. Occipital lobe

5. Hippocampus
 It is part of the limbic system, and lies next to
the medial temporal lobe.
 It is made up of two structures, the Ammon’s
Horn and the Dentate gyrus.
 Damage to the hippocampus and surrounding
area can cause ANTEROGRADE AMNESIA
 The hippocampus is also involved in memory
consolidation, which is the process of
transferring information that is currently in
working memory into ones long-term memory

6.  Hippocampus Promotes Storage of Memories.
When the hippocampi are removed the person
wont be able to store the new memories i.e
both long term and intermediate long-term,
with no capacity to retain declarative
memory. This results in defects of intelligence.
The phenomenon is called as anterograde
amnesia
 Hippocampi are among the most important
output pathways from the “reward” and
“punishment” areas of the limbic system so
they act as path.

7.  Hippocampal lesions can cause both
anterograde and retrograde amnesia.
 When Hippocampus is removed people can
still learn the rapid hand and physical skills
required in many types of sports.

8. Thalamus
 Damage in some thalamic areas may lead
specifically to RETROGRADE AMNESIA.
 Thalamus may play a role in helping the
person “search” the memory storehouses and
thus “read out” the memories
 The memory process not only requires the
storing of memories but also an ability to
search and find the memory at a later date

9. Cerebellum
 It plays an important role in the learning
of procedural memory, and motor learning,
such as skills requiring co-ordination and fine
motor control.
 Specifically it is considered to co-ordinate
timing and accuracy of movements, and to
make long-term changes to improve these
skills. Eg : Calculate the angle and speed at
which you have to kick the ball to make it a
goal.

10. Amygdala
 Located above the hippocampus in the
medial temporal lobes
 There are two amygdalae one on either side.
 They are associated with both emotional
learning and memory, especially to fear
 The neurons here assist in encoding emotional
memories more deeply and accurately.

11.  The amygdala is involved in memory
consolidation.
 Greater the emotional arousal at the time of
the event, the greater the chance that the
event will be remembered.
 The memory is processed at a deeper level
and is likely to withstand forgetting.

12. Basal Ganglia
 The basal ganglia are a group
of nuclei which are located in the medial
temporal lobe, above the thalamus and
connected to the cerebral cortex.
 Basal ganglia includes
1. Subthalamic nucleus,
2. Substantia nigra,
3. Globus pallidus consistsing of
the putamen and the caudate nucleus.

13.  Basal ganglia are also associated with
learning, memory, and unconscious memory
processes, such as motor skills and implicit
memory.
 Damage to the basal ganglia has been linked
to dysfunctional learning of motor and
perceptual-motor skills

14. Frontal lobe
 It is very important in the coordination of
information
 Tthe frontal lobes are important in working
memory Eg : selecting the best route to get to
shopping mall
 It can coordinate various types of
information into a coherent memory trace.
 The frontal lobes are also involved in the
ability to remember what we need to do in
the future

15. Temporal lobe
 Concerned with recognition memory
 Capacity to identify an item as one that was
recently encountered
 Damage to the temporal lobe can affect as
disturbance of auditory sensation and
perception, disorders of visual perception
 Temporal lobe damage can impair long-term
memory

16. Parietal lobe
 Constructing a spatial coordinate system to
represent the world around us
 Parietal lobe also assists with verbal short
term memory
 Damage to the parietal lobe results in the
syndrome ‘neglect’

17.  Damage to the left side of the brain can
lead to language discrepancies, i.e difficulty
in properly identifying letters, numbers and
words, inability to incorporate visual stimuli to
comprehend multiple ways an object can be
found
 Right side damage causes non-verbal
problems, i.e. identifying geometric shapes,
perception of figures and faces

18. Brain Facts
 Being sleep-deprived might make you more
likely to remember stuff that didn’t happen.
 Scientific research has shown that the human
brain starts remembering things from the
womb—memory begins to work 20 weeks after
conception.
 It is believed that an adult can remember
twenty to one hundred thousand words

19. Physiology of Memory

20. Roles of Synaptic
Facilitation and Synaptic
Inhibition
 Memories are stored in the brain by changing
the basic sensitivity of synaptic
transmission between neurons.
 New or facilitated pathways are called
memory traces, once the traces are
established, they can be selectively
activated by the thinking mind to reproduce
the memories

21. Positive and Negative
Memory
 We often think of memories as being positive
recollections of previous thoughts or experiences,
greater share of our memories are negative
memories, not positive.
 The brain gets sensory input from many organs,
and if we have to remember all brain would be
full of memory in minutes
 But brain has capacity to ignore those and this
results from inhibition of synaptic pathways
and the resulting effect is called as Habituation.
This an example for negative memory

22.  Stimulus like pain or pleasure the brain has
different capability for storing memory. This
is called Positive memory and is a result of
facilitation of synaptic pathways and it is
called Memory Sensitization.
 Special areas in brain determine the stimulus
to be stored or to be supressed.

23. Classification of Memories –
Based on Duration
 Short-term memory : memories that last for
seconds or at most minutes unless they are
converted into longer-term memories
 Intermediate long-term memories : last for days
to weeks but then fade away
 Long-term memory : which, once stored, can be
recalled up to years or even a lifetime later.
 Working memory : includes mainly short-term
memory that is used during the course of
intellectual reasoning but is terminated as each
stage of the problem is resolved.

24. Classification of Memories –
Based on type of Information
 Declarative memory : memory of the various
details of an integrated thought like
1. memory of the surroundings,
2. memory of time relationships.
 Skill memory : frequently associated with motor
activities of the person’s body like
1. Calculate the relationship and speed of the ball
to the racquet
2. Reducing the speed and balancing a motor cycle
in a curved road.

25. Short-Term Memory
 Typified by one’s memory of 7 to 10 numerals
in a telephone number and is for few seconds to
minutes and lasts as long as person is thinking
about it.
Theories are :
 Is caused by continual neural activity that travel
around and around a temporary memory trace in
a circuit of reverberating neurons.
 Presynaptic facilitation and inhibition at the
synapse that lie on terminal nerve fibril which on
repeated facilitation helps keep the memory
and we forget as inhibition starts.

26. Intermediate Long-Term
Memory
 They will eventually be lost unless the
memory traces are activated enough to
become more permanent.
 Intermediate long-term type can result from
temporary chemical or physical changes
either in pre or postsynaptic terminal for
minutes to weeks.

27. Chemical Changes in the Presynaptic
Terminal or Postsynaptic Neuronal
Membrane
 Mechanism of memory studied especially by
Kandel and his colleagues

28.  There are two synaptic terminals sensory
terminal and facilitator terminal
 When sensory terminal is stimulated without
the facilitator terminal stimulation, initiallly
signal transmission is great and becomes
weak with repeated stimulus and transmission
caeses and is called habituation and forms a
negative memory.

29.  If the stimulus like noxious stimluls excites
facilitator terminal at the same time when
sensory terminal is stimulated the transmission
becomes stronger and stronger and will
remain even upto 3 weeks without
restimulation.

30. Mechanism for Habituation
 Results from progressive closure of calcium
channels through the terminal membrane.
Less of calcium is released and thus less of
neurotransmitter release.

31. Mechanism for Facilitation
 serotonin release at the facilitator synapse on
the surface of the sensory terminal.
 serotonin acts on serotonin receptors in the
sensory terminal membrane
 activate the enzyme adenyl cyclase inside the
membrane
 formation of cyclic adenosine monophosphate
inside sensory presynaptic terminal

32.  cyclic AMP activates a protein kinase that
causes phosphorylation of a protein
 this in turn blocks the channels for potassium
conductance
 This causes a greatly prolonged action
potential in the synaptic terminal because
potassium ions have to move out for recovery
of action potential
 prolonged action potential causes prolonged
activation of the calcium channels

33.  These calcium ions cause greatly increased
transmitter release by the synapse thereby
markedly facilitating synaptic transmission.
 Studies by Byrne and colleagues, stimuli from
separate sources acting on a single neuron
can cause long-term changes in membrane
properties of the post-synaptic neuron instead
of in the presynaptic neuronal membrane.

34. Long-Term Memory
 long-term memory is generally believed to
result from actual structural changes, instead
of only chemical changes, at the synapses.

35. The most important of the physical structural
changes that occur are the following:
1. Increase in vesicle release sites for secretion
of transmitter substance.
2. Increase in number of transmitter vesicles
released.
3. Increase in number of presynaptic terminals.
4. Changes in structures of the dendritic spines
that permit transmission of stronger signals.

36. Consolidation of Memory
 That is, the short-term memory if activated
repeatedly will initiate chemical, physical, and
anatomical changes in the synapses that are
responsible for the long-term type of memory
 This process requires 5 to 10 minutes for
minimal consolidation and 1 hour or more for
strong consolidation.

37. Rehearsal
 rehearsal of the same information again and
again in the mind accelerates and enhances
consolidation.
 The brain has a natural tendency to rehearse
new found information, especially newfound
information that catches the mind’s attention
Eg :
1. person can remember small amounts of
information studied in depth far better than
large amounts of information studied only
superficially

38. New Memories
 New memories are codified into different classes of
information.
 similar types of information are pulled from the
memory storage bins and used to help process the
new information
 new and old are compared for similarities and
differences rather than storing information
unprocessed
 new memories are not stored randomly in the brain
but are stored in direct association with other
memories of the same type.
 This is necessary if one is to be able to “search” the
memory store at a later date to find the required

39. Brain Facts
 Our memory can associate a scent with a
certain event or occurrence. A smell can
trigger the memory in your mind associated
with it
 No one knows for sure, but the latest estimate
is that our brains contain roughly 86 billion
brain cells.
 Each neuron connects with, on average,
40,000 synapses
 Brain information moves at an impressive 260
miles per hour. This is faster than Formula 1
race cars which top out at 240 mph

40. Disorders of memory
A) The Amnesias
1. Psychogenic
2. Organic
B) Memory Distortions
1. Distortions of Recall
2. Distortion of recognition

41. Amnesia
 It is s a deficit in memory caused by brain
damage, disease, or psychological trauma.

42. Psychogenic Amnesia
 There may be Underlying mental conflicts and
these interfere with perception and
comprehension and resolve with resolution of
underlying conflicts
Eg :
1. Dream Amnesia
2. Defensive Amnesia
3. Anxiety Amnesia

43. Organic Amnesia
 It is true amnesia and affect different functions
of memory. Impairment of registration,
retention, recall may be present.

44.  Acute Coarse Brain Disease :
Retrograde amnesia due to head injury and may
occur in minute to hours or subacutely over
years. Anterograde Amnesia after blackouts
and in delirious patient.

45.  Subacute Coarse Brain Disease :
Unable to register new memory and inability to
learn new information. Seen in damage to
floor and wall of 3rd ventricle and temporal
lobe.
When the thinking progress in a direction it
remains in same irrespective of new stimulus
and is called line thinking.

46. Chronic coarse brain disease :
Amnesia extending over years and memories of
recent events are lost before the remote
events. This is known as RIBOT’S LAW OF
MEMORY REGRESSION.

47. Amnestic Syndromes
Transient Global Amnesia :
Temporary and near total disruption of short term
memory with problems of assessing older
memories.
Cognition is not impaired but patient will be able to
recall deeply encoded memory like his/her name
During an attack of TGA has almost no capacity to
establish new memories, but generally appears
otherwise mentally alert and lucid, possessing full
knowledge of self-identity and identity of close
family, and maintaining intact perceptual skills

48. Korsakoff Syndrome
 Caused due to thiamine (B1) deficiency.
 It affects on medial part of thalamus and
mamillary bodies
 Anterograde and retrograde amnesia are
present
 Confabulations

49. Memory Distortions
Disorders of recall
1. Retrospective Falsification : Unintentional
distortion of memory during emotional,
depressive and maniac state where patient
modifies his memories.
2. Retrospective Delusions : Seen in some
psychotics, Fragments of memories are mixed
with delusions and expressed out
3. Delusional memories : Delusional Experiences
take the form of true memory.
4. Confabulation : Weaving of memory. The gaps
are filled with false memory

50. Disorders of recognition :
1. Déjà vu : feeling of experienced the current
event in the past although it has no basis in
fact
2. Jamais vu : feeling or experience that a
person knows or recognizes a situation, but
that it still seems very unfamiliar or unknown.

51. Brain Facts
 The average brain has around 50,000
thoughts per day and 70% of them are
believed to be negative
 Multitasking makes you less productive. When
you multitask, your brain simply rapidly toggles
back and forth between tasks. This results in
decreases in attention span, learning,
performance, and short-term memory
 Your brain’s storage capacity is considered
virtually unlimited. It doesn’t get “used up” like
RAM in your computer.

52. Dementia
 Memory is the most common cognitive ability
lost with dementia
 In addition to memory, language, visuospatial
ability, calculation, judgment, and problem
solving.
 Dementias result from the disruption of specific
large-scale neuronal networks, features
depends on location and severity of synaptic
and neuronal loss.

53.  In Alzheimer’s disease the disease begins at
transentorhinal region, spreads to the
hippocampus, and then moves to lateral and
posterior temporal and parietal neocortex and
more wide spread region.
 Vascular dementia is associated with focal
damage in a random patchwork of cortical and
subcortical regions or white matter tracts
 Frontotemporal dementia (FTD) or Huntington's
disease (HD) are less likely to begin with memory
problems and more likely to have difficulties with
judgment, mood, and behavior

54. Alzheimer’s Disease
 Begins with memory impairment, early stages
memory loss go unrecognized.
 earliest and most severe degeneration is
usually found in the medial temporal lobe
lateral temporal cortex
 The characteristic microscopic findings are
neuritic plaques and NFTs
 Decrease in the cortical levels of several
proteins and neurotransmitters, especially
acetylcholine, nicotinic cholinergic receptors

55. Vascular Dementia
 Multi-infarct dementia and Diffuse white matter
disease are the two types.
 Several attacks of stroke may develop chronic
cognitive deficits, commonly called multi-
infarct dementia
 Bilateral abnormalities of subcortical white
matter on MRI is termed as diffuse white
matter disease. The dementia may be
insidious in onset and progress slowly in
contast to multi-infarct type.

56. Memory disorders in pediatric
age
 The cause may be direct brain injury (trauma
or CVA) or genetic anomalies.
 A number of genetic syndromes are also
characterized by poor short-term memory
spans like verbal short-term memory, such as
in Down syndrome (trisomy 21) or for visual
short-term memory, such as in Williams
syndrome

57.  Velo-cardio-facial syndrome is particularly
interesting here since a specific deficit for the
retention of order information has been
observed: affected children can accurately
maintain and reproduce the items.
 Epileptic disorders, especially those involving
the medial temporal lobes, are a further
frequent cause of episodic memory deficits

58. Brain facts
 3 = pounds weight
 4 to 6 = minutes brain survive without oxygen
 8 to 10 = seconds of blood loss cause syncope
 10 to 23 = watt of energy produced by brain
when awake
 20 = % of oxygen is used by brain
 1,000 to 10,000 = the number of synapses for
each neuron
 100,000 = miles of blood vessels in your brain
 100 billion = the number of neurons in your brain

59. Neural Implants
 Storing photos, documents
and other files in brain-
implantable liquid could one
day be a reality
 Scientists at the University of
Michigan realized that digital
information could be stored
on colloidal clusters
 microscopic particles
suspended in CSF are tested
in animals

60. Prosthetic Neuronal Memory
Silicon Chip
 It imitates the brain’s process of creating long-
term memories.
 Designed by Theodore Berger, a Biomedical
Engineer and Neurologist at University of
Southern California
 Berger impaired the rats ability to form long-term
memories by using pharmacological agents. The
researchers then developed an artificial
hippocampus. After implanting the artificial
hippocampi into the rats, their ability to identify the
correct lever to pull improved dramatically

61. Brain implants that can help jog our
memories
 US Defense Advanced Research Projects
Agency (DARPA) working on those who have
suffered from traumatic brain injuries
 The team placed small electrode arrays in the
areas of the brain known to be responsible for
the formation of declarative memory. When
tested, their powers of recall were improved.