MEMORYLECTURE - 13

DR. ZAHOOR ALI SHAIKH

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HIGHER FUNCTIONS OF BRAIN:LEARNINGMEMORYJUDGEMENTLANGUAGESPEECH

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WE WILL DISCUSS MEMORY UNDER THE FOLLOWING HEADINGS:WHAT IS MEMORY?WHERE IS MEMORY STORED?CLASSIFICATION OF MEMORYHOW STORAGE OF MEMORY OCCURS?MOLECULAR MECHANISM

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Cont….TERMINOLOGY USED (REMEMBER THE

WORDS)

RECALL MECHANISMCAUSES OF LOSS OF MEMORYHOW TO TEST THE MEMORY

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WHAT IS MEMORY? (LONG TERM)MEMORY IS STORAGE OF ACQUIRED

KNOWLEDGE FOR LATTER RECALLWE KNOW LITTLE ABOUT THE

MECHANISM OF MEMORY

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MEMORY INVOLVESRECEPTION OF INFORMATIONFORMATION OF MEMORY TRACE CONSOLIDATION OF MEMORY TRACERECALL OF MEMORY TRACE

SEQUENCE OF EVENTS IN MEMORYNEWLY 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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IMPORTANTHIPPOCAMPUS – 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 BEPOSITIVENEGATIVE

o POSITIVEMEMORY:o IS ALSO CALLED SENSATISATION OR

FACILITATIONo 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

INHIBITIONIT IS CAPABILITY OF BRAIN TO IGNORE THE

INFORMATION WHICH IS NOT IMPORTANTGREATER SHARE OF OUR MEMORIES ARE

NEGATIVE MEMORYIT IS DUE TO INHIBITION OF SYNAPTIC

PATHWAY•

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(FROM GUYTONS TEXTBOOK OF PHYSIOLOGY) CLASSIFICATION OF MEMORY:

1. SHORT TERM MEMORY• 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 LIFEEg: NUMBER OF PRAYERS PER DAY

DAYS OF THE WEEK

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(FROM GANONGS REVIEW OF PHYSIOLOGY )

CLASSIFICATION OF MEMORY:

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

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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

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MEMORY CLASSIFICATION ACCORDING TO THE TYPE OF INFORMATION [CONT]:

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 OR INHIBITION & SENSITIZATION OR FACILITATION 17

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

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LONG TERM MEMORY: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

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CONSOLIDATION OF MEMORY: (TO REMEMBER) [CONT]

IT TAKES 5 TO 10 MINUTES FOR MINIMAL CONSOLIDATION AND ONE HOUR OR MORE FOR STRONG CONSOLIDATION

SOME FACTORS PREVENT CONSOLIDATIONHEAD INJURY – BRAIN CONCUSSIONDEEP GENERAL ANAESTHESIA – SUDDENLY

APPLIEDELECTRICALLY 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

PASTPRESENTACCIDENT

RETROGRADE MEMORYBEFORE THE ACCIDENT

ANTEROGRADE MEMORYAFTER 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 MEMORYLONG TERM MEMORY

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TERMINOLOGY USED IN MEMORY [CONT]:

WORKING MEMORYMEMORY 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 SOUNDSIMILAR SMELLSIMILAR VIEWSIMILAR WORDS

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DEMENTIAIMPAIMENT 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 INFORMATION3 SPECIES HAVE BRAIN LARGER THAN

HUMANSI. ELEPHANTII. PORPOISEIII. 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 MEMORYPATHALOGICAL CHANGES ARE SEEN IN

MAMILLARY BODIES WHICH HAS EXTENSIVE CONNECTIONS TO THE HIPPOCAMPUS 33

IMPORTANT AREAS FOR . . . SHORT TERM MEMORY – HIPPOCAMPUS,

MEDIAL TEMPORAL LOBELONG TERM MEMORY – NEOCORTEXDECLARATIVE OR EXPRESSIVE OR EXPLICIT

MEMORY – HIPPOCAMPUSSKILL OR IMPLICIT OR NON DECLARATIVE

MEMORY – CEREBELLUM, BASAL GANGLIA.WORKING MEMORY – PREFRONTAL CORTEXMEMORIES 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 DEMENTIANOTE 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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MEMORYMETHOD 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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