Transcript MEMORY

LECTURE - 13
DR. ZAHOOR ALI SHAIKH
1
HIGHER FUNCTIONS OF BRAIN:
 LEARNING
 MEMORY
 JUDGEMENT
 LANGUAGE
 SPEECH
2
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
3
Cont….
 TERMINOLOGY USED (REMEMBER THE WORDS)
 RECALL MECHANISM
 CAUSES OF LOSS OF MEMORY
 HOW TO TEST THE MEMORY
4
WHAT IS MEMORY?
(LONG TERM)
 MEMORY IS STORAGE OF ACQUIRED
KNOWLEDGE FOR LATTER RECALL
 WE KNOW LITTLE ABOUT THE MECHANISM OF
MEMORY
5
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
6
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
7
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
8
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
9
MEMORY MAY BE
 POSITIVE
 NEGATIVE
o POSITIVEMEMORY:
o IS ALSO CALLED SENSATIZATION 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
10
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
•
11
(FROM GUYTONS TEXTBOOK OF PHYSIOLOGY)
CLASSIFICATION OF MEMORY:
SHORT TERM MEMORY
1.
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
12
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
13
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.
14
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
15
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
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
17
HOW MEMORY IS STORED:
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
18
APLYSIA
19
MEMORY SYSTEM THAT HAS BEEN DISCOVERED IN THE SNAIL APLYSIA
20
APLYSIA
21
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
22
LONG TERM MEMORY:
 NAME OF POSITIVE REGULATORY PROTEIN FOR
LONG TERM MEMORY IS “CREB” , A MOLECULAR
SWITCH THAT ACTIVATES LONG TERM MEMORY
STORAGE.
23
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
24
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 CONSOLIDATION
 HEAD INJURY – BRAIN CONCUSSION
 DEEP GENERAL ANAESTHESIA – SUDDENLY
APPLIED
 ELECTRICALLY INDUCED BRAIN CONVULSIONS
25
26
LOSS OF MEMORY (AMNESIA):
RETROGRADE AMNESIA

LOSS OF MEMORY BEFORE THE ACCIDENT
ANTEROGRADE AMNESIA

LOSS OF MEMORY AFTER THE ACCIDENT
27
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 , LITTLE RETROGRADE.
• THALAMIC LESION MAINLY RETROGRADE AMNESIA
• THEREFORE IT SHOWS HIPPOCAMPUS IS RESPONSIBLE FOR NEW
MEMORIES AND THALAMUS STORES OLD MEMORIES
28
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
29
TERMINOLOGY USED IN
MEMORY [CONT]:
 WORKING MEMORY
 MEMORY ACCORDING TO TYPE OF INFORMATION


DECLARATIVE MEMORY
SKILL MEMORY
AMNESIA OR LOSS OF MEMORY


RETROGRADE AMNESIA
ANTEROGRADE AMNESIA
30
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
31
DEMENTIA
 IMPAIMENT OF
MEMORY,
INTELLIGENCE
AND
PERSONALITY
WITHOUT
IMPAIRMENT OF
CONSCIOUSNESS
32
 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,
33
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.
34
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
35
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
36
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
37
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
38
HOW IMPORTANT IS MEMORY . . .
 IMAGINE IF WE WERE WITHOUT MEMORY, 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.
39
THANK YOU
40