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MEMORY

MEMORY. DR. ZAHOOR ALI SHAIKH. HIGHER FUNCTIONS OF BRAIN: LEARNING MEMORY JUDGEMENT LANGUAGE SPEECH. 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. Cont….

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MEMORY

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  1. MEMORY DR. ZAHOOR ALI SHAIKH

  2. HIGHER FUNCTIONS OF BRAIN: • LEARNING • MEMORY • JUDGEMENT • LANGUAGE • SPEECH

  3. 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

  4. Cont…. • TERMINOLOGY USED (REMEMBER THE WORDS) • RECALL MECHANISM • CAUSES OF LOSS OF MEMORY • HOW TO TEST THE MEMORY

  5. WHAT IS MEMORY? (LONG TERM) • MEMORY IS STORAGE OF ACQUIRED KNOWLEDGE FOR LATTER RECALL • WE KNOW LITTLE ABOUT THE MECHANISM OF MEMORY

  6. 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

  7. 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

  8. 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

  9. 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

  10. MEMORY MAY BE • POSITIVE • NEGATIVE • POSITIVEMEMORY: • IS ALSO CALLED SENSATISATION OR FACILITATION • IT IS DUE TO STORAGE OF MEMORY TRACES & RECOLLECTION OF PREVIOUS THOUGHTS OR EXPERIENCES • IT OCCURS DUE TO FACILITATION OF SYNAPTIC PATHWAYS

  11. 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

  12. (FROM GUYTONS TEXTBOOK OF PHYSIOLOGY) • CLASSIFICATION OF MEMORY: • 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 • INTERMEDIATE LONG TERM MEMORY: • LASTS FOR MINUTES, HOURS, DAYS TO WEEKS, BUT THEN THEY WILL BE LOST ( UNLESS CONVERTED TO LONG TERM MEMORY) • 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

  13. (FROM GANONGS REVIEW OF PHYSIOLOGY ) • CLASSIFICATION OF MEMORY: • 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 • LONG TERM MEMORY: • WHICH LAST FOR DAYS, MONTHS, YEARS OR LIFETIME We will follow this classification as Ganong is your text book

  14. 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.

  15. 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

  16. 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

  17. APLYSIA

  18. MEMORY SYSTEM THAT HAS BEEN DISCOVERED IN THE SNAIL APLYSIA

  19. APLYSIA

  20. 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.

  21. 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

  22. LOSS OF MEMORY (AMNESIA): • RETROGRADE AMNESIA • LOSS OF MEMORY BEFORE THE ACCIDENT • ANTEROGRADE AMNESIA • LOSS OF MEMORY AFTER THE ACCIDENT

  23. AMNESIA PAST ACCIDENT PRESENT RETROGRADE MEMORY BEFORE THE ACCIDENT 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

  24. 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

  25. 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

  26. DEMENTIA • IMPAIMENT OF MEMORY, INTELLIGENCE AND PERSONALITY WITHOUT IMPAIRMENT OF CONSCIOUSNESS

  27. 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,

  28. INTRESTING INFORMATION • 3 SPECIES HAVE BRAIN LARGER THAN HUMANS • ELEPHANT • PORPOISE • 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

  29. 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.

  30. 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

  31. 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

  32. 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

  33. 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.

  34. THANK YOU

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