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Please go watch these 2 lectures after class
2008 HHMI lecture by Eric Kandel and Tom JessellThis weekhttp://media.hhmi.org/hl/08Lect1.htmlMore history about early works on mapping the brain function
Next weekhttp://media.hhmi.org/hl/08Lect4.html
Where is the seat of the soul?
Socrates (469-399 BC)“… brain may be the originating power of the perceptions of hearing and sight and smell, and memory and opinion may come from them…”
Aristotle (384-322 BC)cardiocentric view of mental functionfunction of the brain is to cool the heart
Hermann Ebbinghaus The 1st psychologist study memory scientifically.Used introspection to study forgetting in himself list of 12-16 consonant-vowel-consonant nonsense syllabus (Ex:KEG, MIW).
The study of learning is closely related to the beginning of experimental psychology (~1900)
Origins of the study of learning and memory
On Memory: An Investigation in Experimental Psychology in 1885.
Several modern disciplines study of learning and memory
• Psychology– classification of learning and memory
• Physiology/Anatomy – Which part of brain is important for learning and memory
• Molecular Biology– Molecular mechanism of learning and memory
Patient HM
Most famous case reported by Scoville & Milner (1957)
HM: bilateral medial temporal lobe lesion for status epilepticus in 1953
The medial temporal lobe and memory storage
Importance of hippocampus in long-term memory formation: case of H.M.
Amnesia: severe memory loss
1. Retrograde amnesia: cannot recall events that occurred prior to the brain trauma.2. Anterograde amnesia: cannot recall events that occurs after the brain trauma.
Amnesia: Partial or total loss of memory, usually resulting from shock, psychological disturbance, brain injury, or illness.
H.M. showed normal motor learning and long term memory
Subjects were presented with common words
1. asked to recall the words (free recall)2. given the first three letters of a word
(priming)
H.M. perform well in priming
Evidence of postmorbid acquisition of semantic knowledge
H.M.‘s specific memory deficit
• IQ and personality unchanged
• Normal learning and short-term memory
• Normal long-term memory for facts before operation
• Loss of information acquired just before the operation
• Unable to transfer new short-term memory into new long-term
memory (explicit memory)
• Normal procedural (motor) memory
What we learn from H.M.’s case
• We have two types of memory: Short term and long term.
• The hippocampus is not involved in the formation of short term memory and retrieval of long-term memories.
• The hippocampus is not involved in 'procedural memories‘.
• The hippocampus is not be involved in personality, IQ and other cognitive functions.
• The hippocampus is involved in transferring short term explicit memory to long term memory.
The anatomical organization of the hippocampus
pyramidal cell layer
CA=Cornu AmmonisDG=dentate gyrusSub=subiculumEC= Entorhinal Cortex
Hippocampus anatomy
sub
hilus granular cell layer
The input and output pathways of the hippocampal formation
Right hippocampus - spatial memories
London Taxi Drivers : Structural MRI & Neuropsychological Analysis
Bus drivers were not found such correlation
Memory
• Types of memory:
– short-term (working) memory• temporary • limited capacity • needs rehearsal
– long-term memory• 'permanent'• greater capacity • no continual rehearsal needed
Short-term memory• Works like RAM memory in computers; provides a working space.• A limited capacity for 7±2 independent information.• Last only few seconds to minutes• Vulnerable to interruption or interference• The information held in short-term memory may be:– recently processed sensory input– items recently retrieved from long-term memory
Ways to move information to long term memory
1. Senses and emotions2. Repetition and Rehearsal
3. Organization Principles
Senses and emotions
Where were you on the following day?
September 01, 2004
September 11, 2001
September 21, 1999
0-9-3-5-1-5-7-3-7-6
25
Repetition and Rehearsal
Effortful learning usually requires rehearsal or conscious repetition.
Ebbinghaus studied rehearsal by using nonsense syllables: TUV YOF GEK XOZ
Organization Principles
Acronyms are another way of chunking information to remember it.
HOMES = Huron, Ontario, Michigan, Erie, Superior
abuse
Ab = away, from
Long-term memory
• Long-term memory store containing the accumulated knowledge base
• Characteristics– Duration: Hours to years– Capacity: Huge - possibly limitless
Hippocampal system would mediate the initial steps of long-term storage. It would then slowly transfer information into the neocortical storage system.
Forms of long-term memory
Explicit Implicit
Memory can be classified as implicate or explicit on the basis of how information is stored and recalled
Explicit versus Implicit Memory
Explicit (or declarative) memory – recalled by a deliberate, conscious effort.
- semantic memory (facts) - episodic memory (events)
Implicit memory ( nondeclarative) – a memory that is recalled unconsciously. Stored in perceptual, motor and emotional circuits.
- procedural memory (swimming, biking) - associative learning (conditioning) - nonassociative learning - priming
Semantic vs. episodic memory
Episodic Memory refers to memories for particular events that have been experienced.
Semantic Memory refers to knowledge such as vocabularies, concepts, numbers or facts.
associative agnosia apperceptive agnosia
damage to the posterior parietal cortex damage to the occipital lobes
Selective lesions in the posterior parietal cortex produce selective defects in semantic knowledge
Explicit knowledge involves four distinct processes
Encoding: process of newly learned information.
Consolidation: make new information more stable for long-term storage. Synthesis of new proteins is required.Storage: the mechanism and sites to retain memory over time.
Retrieval: recall and use of the stored information.
The more association, the stronger memory
Retrieval of information is most effective when it occurs in the same cues.
Implicit memory
Implicit memory ( nondeclarative) – a memory that is recalled unconsciously. Stored in perceptual, motor and emotional circuits.
- procedural memory (swimming, biking) - associative learning (conditioning) - nonassociative learning - priming
Builds up slowly, through repetition over many trials, and is expressed primarily in performance, not in words.
Does not depend on conscious processes.
Learning of implicit memory
• Non-associative learning: learns about the properties of a single stimulus – Habituation– Sensitization
• Associative learning: learns about the relationship between two stimuli or between a stimulus and a behavior– Classical conditioning (Pavlovian conditioning)– Operant conditioning (Instrumental conditioning)
Nonassociative Learning
Habituation : decrease in response to a repeated stimulus not accompanied by changes in other stimuli
Sensitisation: an increase in response to a moderate stimuli as a result of a previous exposure to a strong stimulus
如入鮑魚之肆，久而不聞其臭 一朝被蛇咬，十年怕草繩
Associative Learning
Classical conditioning Operant conditioning
learning a relationship between two stimuli
learning a relationship between a behavior and the consequences
US → URCS+ US → URCS → CR（ salivation）
(US)
(CS)
(UR)(CR)
Classical conditioning
Classical Conditioning– Unconditioned stimulus (US): unrelated to the response that
eventually will be learned.– Conditioned stimulus (CS): neutral response– During conditioning, the CS and US are paired over many trials– Test of learning: Does the CS alone produce a response?
CS-US paired
CR
TRIALSUR
Pavlov believed that conditioning strengthened connections between the CS center and US center in the brain.
Pavlov’s view of the physiology of learning
Contest vs. cued fear conditioning
• CS= something neutral (tone, light)• US= aversive stimulus (loud noise, shock )
The formation of classical conditioned response depend on the correlation between CS and US
10 Tone-Shock Pairings 10 Tone only 1 Tone-Shock Pairings
ExtinctionTraining Re-train
Extinction and spontaneous recovery
ExtinctionTraining Re-train
Remote training
10 Tone-Shock Pairings
Freezing
Importance of hippocampus in contextual fear conditioning test
Remote Training
Recent Training
10 light-Shock Pairings
50 days later
Importance of hippocampus in contextual fear conditioning test
Lesion
SHAMDH
0
–2
–3
–6
AP
Electrolytic Dorsal Hippocampus Lesion
With in 24 hr
Importance of hippocampus in contextual fear conditioning test
Remote Training
Recent Training
50 days later
Sham or Hippocampus
Lesion
DH
SHAM
next day
10 day recovery
C
0
RecentRemote
(first six min)
25
50
75
100
% f
reezi
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Importance of hippocampus in contextual fear conditioning test
Remote Training
Recent Training
50 days later
Remote Recent
Next day
Operant Behavior
• Associative learning process between a stimulus and a response.
• The term operant comes from the verb to operate and refers to behavior that operates on the environment to produce a consequence.
• Not automatic• Operant conditioning as a process, has evolved over species
history and is based on genetic endowment.
Operant learning
• The mouse is “operating” on its environment by pressing the lever in the box and receiving a food reward.
• Voluntary and goal directed• Controlled by its
consequences• Strengthened if rewarded or
punished
Associative learning is not random but is constrained by the biology of the organism
Hebbian learning
• Donald Hebb (1949) - When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A's efficiency, as one of the cells firing B, is increased.
