Transcript MEMORY PSL 132

DR. ZAHOOR ALI SHAIKH
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 HIGHER FUNCTIONS OF BRAIN:
 LEARNING
 MEMORY
 JUDGEMENT
 LANGUAGE
 SPEECH
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 WE WILL DISCUSS MEMORY UNDER THE
FOLLOWING HEADINGS:
 WHAT IS MEMORY?
 WHERE IS MEMORY STORED?
 CLASSIFICATION OF MEMORY
 HOW STORAGE OF MEMORY OCCURS?

MOLECULAR MECHANISM
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Cont….
 TERMINOLOGY USED (REMEMBER THE WORDS)
 RECALL MECHANISM
 CAUSES OF LOSS OF MEMORY
 HOW TO TEST THE MEMORY
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 WHAT IS MEMORY? (LONG TERM)
 MEMORY IS STORAGE OF ACQUIRED
KNOWLEDGE FOR LATTER RECALL
 WE KNOW LITTLE ABOUT THE MECHANISM OF
MEMORY
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 MEMORY INVOLVES
 RECEPTION OF INFORMATION
 FORMATION OF MEMORY TRACE
 CONSOLIDATION OF MEMORY TRACE
 RECALL OF MEMORY TRACE
 SEQUENCE OF EVENTS IN MEMORY
 NEWLY ACQUIERED INFORMATION – SHORT TERM
MEMORY (USUALLY LOST) OR IT IS TRANSFERRED
TO LONG TERM MEMORY BY REHERSAL –
CONSOLIDATION INTO LONG TERM MEMORY
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 WHERE IS MEMORY STORED?
 MEMORIES ARE STORED IN THE BRAIN AT
SYNAPSES BY CHANGING THE BASIC SENSITIVITY
OF SYNAPTIC TRANSMISSION BETWEEN
NEURONS. WE CREATE A MEMORY TRACE
 MEMORY TRACE:


THE NEURAL CHANGE AT SYNAPSES WHICH IS
RESPONSIBLE FOR RETENTION OR STORAGE OF
KNOWLEDGE IS KNOWN AS MEMORY TRACE.
ONCE MEMORY TRACE ARE ESTABLISHED, THEY CAN BE
ACTIVATED BY THINKING MIND TO REPRODUCE
MEMORY
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 WHAT PARTS OF BRAIN ARE RESPONSIBLE FOR
MEMORY?
 MEMORY TRACES OCCUR AT MANY REGIONS OF BRAIN
AT CORTICAL AND SUBCORTICAL REGIONS. THERE IS
NO SINGLE MEMORY CENTER
 THE IMPORTANT MEMORY AREA ARE:






CEREBRAL CORTEX (MOTOR,SENSORY,VISUAL AUDITORY)
PREFRONTAL CORTEX
HIPPOCAMPUS & MEDIAL TEMPORAL LOBE
LIMBIC SYSTEM
THALAMUS
CEREBELLUM
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IMPORTANT
 HIPPOCAMPUS – MAINTAINS RECORD OF
EVERYDAY EVENTS IN OUR LIFE.
 PERSON WITH HIPPOCAMPUS DAMAGE ARE
EXTREMELY FORGETFULL TO DAILY
FUNCTIONING
 HIPPOCAMPUS IS FOR SHORT TERM MEMORY
 NOTE: IN ALZHEIMERS DISSEASE DAMAGE
OCCURS TO HIPPOCAMPUS REGION THEREFORE
LOSS OF SHORT TERM MEMORY
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 MEMORY MAY BE
 POSITIVE
 NEGATIVE
o POSITIVEMEMORY:
o IS ALSO CALLED SENSATISATION OR FACILITATION
o IT IS DUE TO STORAGE OF MEMORY TRACES &
RECOLLECTION OF PREVIOUS THOUGHTS OR
EXPERIENCES
o IT OCCURS DUE TO FACILITATION OF SYNAPTIC
PATHWAYS
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 NEGATIVE MEMORY:
 IT IS ALSO CALLED HABITUATION OR INHIBITION
 IT IS CAPABILITY OF BRAIN TO IGNORE THE
INFORMATION WHICH IS NOT IMPORTANT
 GREATER SHARE OF OUR MEMORIES ARE
NEGATIVE MEMORY
 IT IS DUE TO INHIBITION OF SYNAPTIC PATHWAY
•
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 CLASSIFICATION OF MEMORY:
SHORT TERM MEMORY
1.
(FROM GUYTONS TEXTBOOK OF PHYSIOLOGY)
MEMORY WHICH LASTS FOR SECONDS TO MINUTES
(UNLESS THEY ARE CONVERTED INTO LONG TERM MEMORIES)
Eg: TO REMEMBER TELEPHONE NUMBER 7 – 10 DIGITS FOR
SECONDS OR MINUTES, TILL YOU ARE THINKING ABOUT
THE NUMBERS
•
2.
INTERMEDIATE LONG TERM MEMORY:
 LASTS FOR MINUTES, HOURS, DAYS TO WEEKS, BUT
THEN THEY WILL BE LOST ( UNLESS CONVERTED TO
LONG TERM MEMORY)
3. LONG TERM MEMORY:
 WHICH ONCE STORED CAN BE RECALLED UP TO YEARS
OR EVEN FOR WHOLE LIFE
 Eg: NUMBER OF PRAYERS PER DAY

DAYS OF THE WEEK
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 CLASSIFICATION OF MEMORY:
(FROM GANONGS REVIEW OF PHYSIOLOGY )
1. SHORT TERM MEMORY:


WHICH LASTS FOR SECONDS TO HOURS –
HIPPOCAMPUS
Eg: MEMORY OF FEW WORDS, NUMBERS, LETTERS
LIMITED TO 7 – 10 NUMBERS LIKE TELEPHONE
NUMBERS, CAR NUMBER
2. LONG TERM MEMORY:

WHICH LAST FOR DAYS, MONTHS, YEARS OR LIFETIME
We will follow this classification as Ganong is your text book
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 ANOTHER TYPE OF MEMORY
 WORKING MEMORY:
 IT INCLUDES MAINLY SHORT TERM MEMORY, THAT IS
USED DURING THE INTELLECTUAL REASONING , BUT IS
TERMINATED AS PROBLEM IS SOLVED. – PREFRONTAL
LOBE IS INVOLVED
 Eg: SEE THE TELEPHONE NUMBER , REMEMBER THE
NUMBER WHILE PICKUP PHONE, DIAL THE NUMBER
AND TALK ABOUT THE PROBLEM Eg: Examination
Preparation
 NOW IT IS THOUGHT THAT INTELLIGENCE DEPENDS
ON WORKING MEMORY.
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 MEMORY CLASSIFICATION ACCORDING TO THE
TYPE OF INFORMATION:
 DECLARATIVE MEMORY OR EXPLICIT MEMORY
 IT IS MEMORY OF SURROUNDINGS, EVENTS, TIME, Eg.
WE PLAYED FOOTBALL GAME TODAY
 DECLARATIVE MEMORY IS DEPENDENT ON
HIPPOCAMPUS
 SKILL MEMORY OR IMPLICIT MEMORY
 IT IS LEARNING OF SKILLS Eg. LEARNING FOOTBALL,
HOW TO HIT OR STRIKE MOVE THE BALL etc.
 SKILLS ONCE ACQIRED BECOME AUTOMATIC
 RETENTION OF SKILLS DOES NOT INVOLVE
HIPPOCAMPUS BUT CEREBELLUM, PRIMARY MOTOR
CORTEX, SOMATOSENSORY CORTEX, VISUAL
PROCESSING AREAS
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 HOW MEMORY IS STORED:
 MEMORY DOES NOT RESIDE IN A SINGLE
NEURON BUT CHANGES OCCUR IN THE PATTERN
OF SIGNALS TRANSMITTED ACROSS SYNAPSES
WITHIN A NORMAL NETWORK
 SHORT TERM MEMORY:
 INVOVES TRANSIENT MODIFICATION IN THE
FUNCTION OF SYNAPSES Eg: AMOUNT OF
NEUROTRANSMITTER RELEASED IN RESPONSE TO
STIMULATION
 EXPERIMENTS ARE DONE IN SEA SNAIL (APLYSIA)
Eg. HABITUATION & SENSITIZATION
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APLYSIA
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MEMORY SYSTEM THAT HAS BEEN DISCOVERED IN THE SNAIL APLYSIA
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APLYSIA
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 LONG TERM MEMORY:
 INVOVES PERMENANT STRUCRURAL CHANGES
BETWEEN EXISTING NEURONS IN THE BRAIN DUE TO
ACTIVATION OF SPECIFIC GENES THAT CONTROL
PROTEIN SYNTHESIS. THESE PROTEINS CAUSE :




FORMATION OF NEW SYNAPTIC CONNECTIONS
GREATER BRANCHING ANDF ELONGATION OF DENDRITES IN
NERVE CELL IN BRAIN AREAS INVOLVED FOR MEMORY
STORAGE.
INCREASE NO. OF VESICLES IN PRESYNAPTIC NEURON
INCREASE NO. OF SIGNAL TRANSMISSION
 NAME OF POSITIVE REGULATORY PROTEIN FOR
LONG TERM MEMORY IS “CREB” , A MOLECULAR
SWITCH THAT ACTIVATES LONG TERM MEMORY
STORAGE.
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 CONSOLIDATION OF MEMORY: (TO REMEMBER)
 FOR SHORT TERM MEMORY TO BE CONVERTED INTO
LONG TERM MEMORY IT MUST BE CONSOLIDATED
 CONSOLIDATION OCCURS BY REPEATEDLY ACTIVATING
THE SHORT TERM MEMORY, WHICH WILL INITIATE
CHEMICAL, PHYSICAL AND ANATOMICAL CHANGE IN
THE SYNAPSES THAT ARE RESPONSIBLE FOR LONG
TERM MEMORY
 IT TAKES 5 TO 10 MINUTES FOR MINIMAL
CONSOLIDATION AND ONE HOUR OR MORE FOR
STRONG CONSOLIDATION
 SOME FACTORS PREVENT CONSOLIDATION
 HEAD INJURY – BRAIN CONCUSSION
 DEEP GENERAL ANAESTHESIA – SUDDENLY APPLIED
 ELECTRICALLY INDUCED BRAIN CONVULSIONS
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 LOSS OF MEMORY (AMNESIA):
 RETROGRADE AMNESIA

LOSS OF MEMORY BEFORE THE ACCIDENT
 ANTEROGRADE AMNESIA

LOSS OF MEMORY AFTER THE ACCIDENT
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AMNESIA
ACCIDENT
PAST
RETROGRADE MEMORY
BEFORE THE ACCIDENT
PRESENT
ANTEROGRADE MEMORY
AFTER THE ACCIDENT
• HIPPOCAMPUS REMOVAL (FOR TEMPORAL LOBE EPILEPSY) OR LESION –
MAINLY ANTEROGRADE AMNESIA
• THALAMIC LESION MAINLY RETROGRADE AMNESIA
• THEREFORE IT SHOWS HIPPOCAMPUS IS RESPONSIBLE FOR NEW
MEMORIES AND THALAMUS STORES OLD MEMORIES
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 TERMINOLOGY USED IN MEMORY:
 MEMORY TRACE: THE NEURAL CHANGE RESPONSIBLE
FOR RETENTION OF KNOWLEDGE IS KNOWN AS
MEMORY TRACE
 SENSITIZATION OR POSITIVE MEMORY OR
FACILITATION
 NEGATIVE MEMORY OR HABITUATION OR INHIBITION
 SHORT TERM MEMORY
 LONG TERM MEMORY
 WORKING MEMORY
 MEMORY ACCORDING TO TYPE OF INFORMATION


DECLARATIVE MEMORY
SKILL MEMORY
 AMNESIA OR LOSS OF MEMORY
 RETROGRADE AMNESIA
 ANTEROGRADE AMNESIA
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 RECALL OF MEMORY:
 ALL COMPONENTS OF MEMORY ARE BROUGHT
TO CONSCIOUSNESS
 RECALL OF MEMORY BY . . . .
 SIMILAR SCENE
 SIMILAR SOUND
 SIMILAR SMELL
 SIMILAR VIEW
 SIMILAR WORDS
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DEMENTIA
 IMPAIMENT OF
MEMORY,
INTELLIGENCE
AND
PERSONALITY
WITHOUT
IMPAIRMENT OF
CONSCIOUSNESS
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 HOW TO TEST THE MEMORY?
 RECENT MEMORY TEST:
 GIVE NAME AND ADDRESS TO REMEMBER (7 – 10
WORDS) THEN ASK 5 MINUTES LATER OR
 GIVE THREE ITEMS WITHIN THE ROOM AND ASK
THE PATIENTS TO REPEAT THEIR NAMES AFTER 5
MINUTES
 DISTANT MEMORY TEST:
 ASK IMPORTANT DATE WHICH PATIENT KNEW
THE ANSWER AND CLINICIAN ALSO KNOWS THE
ANSWER Eg. NATIONAL DAY,
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INTRESTING INFORMATION
 3 SPECIES HAVE BRAIN LARGER THAN HUMANS
I. ELEPHANT
II. PORPOISE
III. WHALE
 BUT IN RELATION TO BODY WEIGHT HUMAN
BRAIN IS LARGE
 WEIGHT OF A HUMAN BRAIN IS ABOUT THREE
POUNDS OR 1.5 KG
 ALCOHOL CAUSES LOSS OF RECENT MEMORY
 PATHALOGICAL CHANGES ARE SEEN IN MAMILLARY
BODIES WHICH HAS EXTENSIVE CONNECTIONS TO THE
HIPPOCAMPUS
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 IMPORTANT AREAS FOR . . .
 SHORT TERM MEMORY – HIPPOCAMPUS, MEDIAL
TEMPORAL LOBE
 LONG TERM MEMORY – NEOCORTEX
 DECLARATIVE OR EXPRESSIVE OR EXPLICIT
MEMORY – HIPPOCAMPUS
 SKILL OR IMPLICIT OR NON DECLARATIVE
MEMORY – CEREBELLUM, BASAL GANGLIA.
 WORKING MEMORY – PREFRONTAL CORTEX
 MEMORIES VISUAL, OLFACTORY, AUDITORY ARE
LOCATED IN RESPECTIVE CORTICAL REGIONS.
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 ALZHEIMER DISEASE
 LOSS OF RECENT MEMORY
 AFFECTED AREAS – HIPPOCAMPUS, MAMMILLARY
BODY, ANT. HYPOTHALAMUS, PREFRONTAL
CORTEX, NEOCORTEX
 THERE IS PROGRESSIVE LOSS OF SHORT TERM MEMORY
AT THE AGE OF 50 YEARS OR AFTER
 NEUROTANSMITTER ACETYLCHOLINE IS LOST DUE TO
LOSS OF SYNAPSES AND NEURONS CAUSED BY TOXIC
PEPTIDE A β1-40 AND A β1-42
 SENILE DEMENTIA
 NOTE SENILE DEMENTIA OCCURS AFTER THE AGE OF
65 YEARS AND IT IS SLOWLY PROGRESSIVE
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 MEMORY
 ESSAY QUESTION EXAM – RECALL MEMORY
(SUBJECTS PRODUCE INFORMATION ON THEIR
OWN)
 MCQ EXAM – RECOGNITION - SUBJECTS IDENTIFY
PREVIOUSLY LEARNED INFORMATION
 RESEARCH SHOWS RECOGNITION IS EASIER
THAN RECALL
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 MEMORY
 METHOD OF STUDY IN HUMANS
 PET SCAN (POSITRIN EMISSION TOMOGRAPHY)

MEASURES LOCAL GLUCOSE METABOLISM WHICH IS
PROPORTIONATE TO THE NEURAL ACTIVITY
 fMRI (FUNCTIONAL MAGNETIC RESONANCE
IMAGING)

Measures local amount of oxygenated blood which tells about
the activity of brain
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 HOW IMPORTANT IS MEMORY . . .
 IMAGINE IF WE WERE WITHOUT IT WE WOULD
NOT RECOGNISE ANYONE, WE WOULD REMEMBER
NOTHING AND WOULD HAVE NO RECOLLECTION
OF THE EVENTS OF OUR OWN LIVES. WE WOULD
HAVE LACK OF KNOWLEDGE AS NEW BORN
BABIES.
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THANK YOU
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