The document discusses the neurobiology of memory. It covers: 1. The key stages of memory including encoding, storing, and recall. Immediate, short-term, working, and long-term memory are described. 2. The neuroanatomical correlates of memory including the hippocampus, medial diencephalon, basal forebrain, prefrontal cortex, and subcortical nuclei. 3. Theories of memory such as the consolidation theory and multiple trace theory. Different classifications of memory like declarative vs procedural are also covered. 4. Assessment of memory function and various clinical types of memory disorders are discussed like amnesia.

1. NEUROBIOLOGY OF MEMORY
Chair: Dr. D. Raju
Co- chair: Dr. Indu P. V.
Presenter: Dr. Indu V. Nair

2. “Memory is a man's real
possession...In nothing else is he
rich, in nothing else is he poor.”
-Alexander Smith (1830 - 1867)

3. Memory - introduction
 A mental process that allows individuals to
store information for later recall.
 Timespan- few seconds to many years
 Commonest problem in organically based
beh. syndromes- dementia, delirium,
amnestic syndromes etc.
 Psych. problems- depression , anxiety,
any emotionally disturbed person
 In trt. –ECT, drugs (benzodiazepines)

4. Stages of memory
1. Information– received & registered, held
in short term memory
2. Storing or retaining information in more
permanent form
3. Recall or retrieval of information

5. Clinical types of memory
Time span b/w stimulus
presentation & memory
Immediate recent remote

6. Immediate memory
 Recall of a memory trace in few seconds
 Repetition of a series of digits
 Requires initial registration, short term
holding, verbal repetition
 Exact mech. not known
 Entire process by language cortex
surrounding Sylvian fissure
 Reverberating circuits, pattern of after
image

7. Contd.
 Reverberating circuits --- neuronal
activity being maintained in a closed loop.
 Sensory register --- Contains only
unprocessed information
 Raw image remains in sensory system
 Fleeting visual image -- icon
 Auditory image -- echo

8. contd
 Can be transferred to STM or working
memory
 Stage of temporary storage, <30 sec.
 Limited capacity
 Av. for adults – 7 +/- 2
 Less for children

9. Contd.
 Many factors favor STM like
 Active mental rehearsal
 Grouping digits
 Association of new material with
previously learned --- digit sequence
similar to old phone no.

10. Contd.
 Intact language system essential in DST,
so aphasia can disrupt memory fn.
Repetition failure notable in conduction
aphasia
 Attention strays during stimulus prsntn.–
information imperfectly registered
 So also in repetition phase
 Impaired in delerium, dementia, anxiety,
depression

11. WORKING MEMORY
 Ability to temporarily store & process
information online.
 Associated with prefrontal portex
• Very flexible
• Capacity to store is limited
• Decays rapidly

12. Working Memory - Compartments

13.  Right Lateralisation
 Inferior Parietal BA 40
 Premotor Cortex BA 6
 Inferior Frontal Cortex BA 47
 Anterior Extrastriate Occipital Cortex BA 19
VISUOSPATIAL WORKING MEMORY

14.  Left Temperoparietal region
 Storage component – BA 40
 Rehearsal component – BA 6/44 (Broca’s)
Phonological Loop

15. DORSOLATERAL PREFRONTAL
SYNDROME
WORKING MEMORY
 Working memory:
 In PFL lesions:
• Severe defect in working memory
• Tested by delayed response task
• Due to interference from extraneous sources:
 ( Distractibility hypothesis)

16. DORSOLATERAL PREFRONTAL
SYNDROME
MEMORY PROBLEMS
 No true memory loss
 Tests of long term memory functions are normal.
 Defects in retrieval
 (“Forgetting to remember”)
 Recall with “ Cues”


17. Recent memory
 Ability to store & retrieve new material
 Needs intact registration, retention & short
term storage
 2 main regions of brain imp. In this fn.
 Hippocampal apparatus
 Hypothalamic diencephalic region

18. Remote memory
 As time passes some memories forgotten,
some get stronger
 Initial encoding, gradual consolidation,& in
retrieval -- med. temporal & diencephalic
structures imp.
 Distributed neocortical regions –
permanent repositories of memory
 Distributed storage system makes LTM
more or less indestructible

19. Neuroanatomical correlates of
memory
1. MTL – hippocampus & related structure
amygdala
2. Medial diencephalon
3. Basal forebrain
4. Prefrontal cortex
5. Sub cortical nuclei & white matter

20. The Day His World Stood Still
by Joanna Schaffhausen
When twenty-seven year old Henry M. entered the hospital in 1953 for
radical brain surgery that was supposed to cure his epilepsy, he was
hopeful that the procedure would change his life for the better. Instead, it
trapped him in a mental time warp where TV is always a new invention
and Truman is forever president. The removal of large sections of his
temporal lobes left Henry unable to form any new personal memories, but
his tragic loss revolutionized the field of psychology and made "H.M." the
most-studied individual in the history of brain research.

21. Dr. Scoville removed a large chunk of Henry's right and left
temporal lobes, which was a crucial decision because the
brain is symmetrical and thus most important structures are
duplicated. Altogether, Henry lost about a fist-sized portion of
his brain, which encompassed (on both sides) the
hippocampus, the amygdala, and the entorhinal and
perirhinal cortices.

22. As for Henry's current status, he lives in a
nursing home in Hartford and still travels
occasionally to MIT for memory testing. He
enjoys doing crossword puzzles and watching
detective shows on television. His life is
peaceful, if not completely happy. He worries
often that he has done something wrong, and
it is not possible for him to make any real
friends since he cannot remember a person
from ten minutes to the next.

24. Contd.
 Hippocampus – initial encoding, processing for a
variable period~ 2 yrs
 Any info. integrated by HC apparatus to form a memory
trace – an ensemble of HC – neocortical neurons
 Rapid consolidation --short term process,
Prolonged consolidation
 lot of work during sleep
 Contributes to REM sleep phenomenon

25. Long term potentiation
 Brief burst of high frequency presynaptic
stimulation
 Persistent depolarisation of post synaptic
neuron
 Induction of LTP mediated post
synaptically via NMDA receptor
 LTP occurs prominently in hippocampus
 The physiological substrate of memory

26. In addition to his well-
lauded, ongoing research at
Columbia University Medical
Center’s New York State
Psychiatric Institute, Kandel
has written several books on
neurobiology, behavior, and
memory. In addition to being
a Nobel Laureate Scientist,
he is well-known as an editor
of the seminal textbook
Principles of Neural Science.
Eric Kandel

27. Mollusc Aplysia popular with research b/c it
has few, very large neurons

28. Contd.
 Kandel showed, STM –change in existing
synapses like in NT release
 LTM –creating new synapses, new protein
syn. ,growth of neural processes

29. Amygdala & memory
 Storage of emotional memory
 Emotional events remembered better than
neutral events
 When emotional more attentive, more
activity in brain
 Unusual events, we tend to go over & over
in our mind
 Emotions usually benefit memory, long
lasting stress detrimental --PTSD

30. Contd.
emotion Brain chem. memory
Excitement Ach&NA Vivid event memories
Pleasure DA Vivid event memories
Disgust Glu Asso memories-
aversion to food
Love Oxytocin Increases familiarity to
loved object
Fear Cortisol Creats fear mem. In
amygdala

32. Diencephalic amnesia
 Exact regions not known
 Mamillary body, mammilothalamic tract,
dorsomedial nu. of thalamus, ant. nucleus,
int. medullary lamina– imp. structures –
Papez circuit
 Korsakoff’s syndrome- best example
 When subcortical structures damaged—
anterograde amnesia,retrograde amnesia,
confabulation in a/c stage

33. HIPPOCAMPUS
MAMILLARY
BODY
ANTERIOR NUCLEUS
OF THALAMUS
CINGULATE GYRUS
PARAHIPPOCAMPAL
GYRUS
ENTORHINAL
CORTEX
FORNIX
MAMILLOTHALAMIC
TRACT
INTERNAL
CAPSULE
CINGULUM
PERFORANT
PATHWAY
Papez Circuit

34. Basal fore brain
 Includes medial septal nuclei, nucleus
accumbens, ant. HT, diagonal band of
Broca, nucleus basalis of Meynert & part
of PFC
 Rich in Ach, imp to memory functioning
 Septal nu. & nu. Basalis of Meynert –
extensive connections to & from HC,
amygdala & neocortex
 Extensive damage seen in Alzheimer’s

35. Sub cortical nuclei & white matter
 Role in searching & retrieving information
from LTM
 Parkinson’s d/s, Huntington’s d/s ,CVA,
MS
 Slowed information processing, inefficient
learning, poor free recall
 Recognition memory good

36. Role of cerebellum
 Contains essential circuitry for learned
association
 Synaptic changes in cere. cortex– learned
timing
 Deep nuclei critical for forming association
b/w conditioned & unconditioned stimuli

37. Theories of memory
 Traditional consolidation model
 Cognitive map theory
 Multiple trace theory – most recent

38. Consolidation theory
 Described by Muller & Pilzecker in 1900
 2 processes described :
 physiological / biochemical process for
formation & storage of a memory trace or
“engram”
 Psychological process needed to
assimilate newly formed memory into
existing knowledge

39. Multiple trace theory
 Each time an old memory is retrieved , a
new hippocampally mediated trace is
created
 Old ones replaced by more or stronger
HC/MTL neocortical traces

40. Different classifications of memory
Declarative Procedural
Explicit Implicit
Accessible to conscious
awareness by recall
Not available to
conscious recall
Hippocampus
&diencephalon
Striatum & neocortex in
habits, cerebellum
conditioning, amygdala
for emotional learning
Disrupted in amnesia preserved

41. Declarative memory
Semantic or knowledge Episodic
Organised knowledge of
world
Personally experienced
events or episodes
Acquired early in life From day to day
experiences
Shared with others, not
held in sp. order
Of personal significance
Less vulnerable More vulnerable in
amnestic syndromes

42. Procedural memory
 Skill learning – riding a bicycle
 Cognitive tasks – solving puzzles
 Simple forms of conditioning
 priming

43. Priming
 Ability to detect or identify a particular
stimulus based on recent experience with
same stimulus
 A distinct class independent of med.
temporal region
 Intact in amnesia
 Neocortex

44. Assessment of memory function
 Immediate memory – DST
 Recent memory -- orientation
new learning ability – 3 object recall
--address recall
--24 hr recall
verbal story for recall
visual memory (hidden object)
paired associate learning
 Remote memory -- remote events –semantic &
episodic

45. metamemory
 Ability to judge one’s own memory ability
 Self rating scales available
 Able to distinguish memory complaints b/w
amnesia & depression
 Depressed patients rate their memory
poor ,self reports match objective tests
 Amnesia –some items more than others,
no difficulty with remote events

46. Psychogenic amnesia
 New learning capacity not affected
 Extensive , severe retrograde amnesia
 Unable to recall even ‘own name’
 Circumscribed memory loss of particular
time periods

47. Infantile amnesia
 Apparent absence for conscious memory
for first 3 yrs of life
 Mech. –repression (psychoanalytic theory)
--retrieval failure (dev. psychology)
-- capacity for decl. memory not
available
 Development & differentiation of neocortex
not complete

48. Retrospective falsification of
memories
 Possible to remember events which never
happened
 ? Same brain regions involved as visual
imagery
 Illusory memories can be created esp in
children
 Important in eyewitness testimony & recall
of traumatic events

49. Future of memory
 Finding memory
replacement
 UCLA in USA---
silicon chips
mimicking
hippocampus

50. Thank you