1 forming memories in the brain : process of consolidation consolidation : transforms new memories...

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Forming memories in the brain :Process of consolidation

Consolidation : transforms new memories from a fragile state to a more permanent state

Levels of reorganization in nervous system :

1. Synaptic consolidation

2. Systems consolidation

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Synaptic consolidation• Occurs at synapses

• Happens rapidly

• Over a period of minutes

Discovered molecular processes involved in synthesizing the proteins that result in structural change at the synapse

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Systems consolidation• Many brain regions

• Gradual reorganization of cortical circuits

• Takes place on a longer time scale, lasting weeks, months, or even years

Importance of hippocampus in consolidation

H.M. lost his ability to form new memories after his hippocampus was removed

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Chapter summery 17

• Consolidation transforms new memories into a state in which they are more resistant to disruption.

• Synaptic consolidation occurs at synapses and is rapid.

• Systems consolidation involves the reorganization of cortical circuits and is slower

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H.M.

Anterograde amnesia

• Removal of H.M.’s hippocampus made it impossible for him to form new memories

Retrograde amnesia (partially)

• Amnesia extended back for about 10-15 years prior to his operation

• He could remember events that occurred before then

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Graded amnesia

• H.M. could remember events from his childhood, but apparently not with as much clarity and detail as a person without brain damage

Graded amnesia = amnesia is most severe for events that occurred just prior to the injury and becomes less severe for earlier, more remote events

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Graded amnesia (retrograde amnesia)

• Memory for recent events is more fragile than memory for remote events

Forming memories in the brain :Fragility of new memories

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Consolidation – Transforms new memories from a fragile

state, in which they can be disrupted, to a more permanent state, in which they are resistant to disruption

• A consolidation process must occur before memories become resistant to being disrupted

Forming memories in the brain :Fragility of new memories

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Hippocampus & consolidation

• Memory retrieval depends on the hippocampus during consolidation

Once consolidation is complete

• Retrieval no longer depends on the hippocampus

Example : Graded amnesia after hippocampectomy

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• Your memory for last new year’s Eve could include sights, sounds, smells, emotions you were feeling and thoughts you were thinking at the stroke of midnight

• Experience results in activity of the different cortical areas

• No connection in the cortex

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• Incoming information activates a number of areas in the cortex.

• Activation is distributed across the cortex because memories typically involve many sensory and cognitive areas.

• Cortex communicates with hippocampus

Standard model of consolidation

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Reactivation

• Hippocampus replays the neural activity associated with a memory

• Results in the formation of connections between the cortical areas

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• Reactivation process occurs during sleep or during periods of relaxed wakefulness

• Reactivation process can be enhanced if a consciously rehearses a memory


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“ Consolidation occurs during sleep ”Peigneux et al.,2004

Walker & Stickgold, 2004

• Finding that memory for learning is enhanced when the learning is immediately followed by a period of sleep


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cortical connections become strong enough

–the different sites in the cortex become directly linked

–hippocampus is no longer necessary


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Chapter summery 18.1The standard model of consolidation proposes that

during consolidation

– Memory retrieval depends on the hippocampus

after consolidation is complete

– Memory retrieval involves the cortex– Hippocampus is no longer involved

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• Retrieval of recent memories depends on the hippocampus, and cortical connections have not yet formed

(a) For retrieval of recent memories, hippocampal activation is high and cortical activation is low

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• Once consolidation has occurred, cortical connections have formed, and the hippocampus is no longer needed.

(b) For retrieval of remote memories, cortical activation is high, and there is no hippocampal activation.


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Recent memory : hippocampus & cortex

Remote memory : cortex only

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Medial temporal lobe & semantic M

MTL do not activated for remote (semantic) memories.

Recently learned memories cause activity in the MTL

Haist 2001 , Wiltgen 2004

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Mental time travel (episodic M) & MTL

• Ryan et al.,2001• Participants engage in mental time travel• fMRI study activity in hippocampus• MTL is activated both when recent episodic

memories and remote episodic memories are retrieved

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Hippocampus is activated during retrieval of both recent and remote memories

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Asaf Gilboa and coworkers 2004

• Showing photographs of themselves engaging in various activities that were taken at times ranging from very recently, to when they were 5 years old

• Results : hippocampus was activated during retrieval of both recent and remote memories.

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Moscovitch & Nadel 1997

• Experiments that demonstrate MTL and HC activation when retrieving remote episodic memories

• Support the idea that the hippocampus and MTL are always important when accessing the details of episodic memories

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Peter Bayley and coworkers 2005

• Describe patients with damage to the MTL who were still able to remember the details of remote episodic memories

• Results fits the standard model

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Support evidence• Haist et al.,2001• Wiltgen et al.,2004• Peter Bayley and

coworkers 2005

Conflict evidence• Ryan et al.,2004• Asaf Gilboa and

coworkers,2004• Moscovitch et

al.,2005• Nadel & Moscovitch,

1997


Recent memory : hippocampus & cortex

Remote memory : cortex only

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Chapter summery 18.2

• There is evidence supporting the standard model of consolidation,

and also evidence supporting the idea that retrieval of episodic memories always involves the hippocampus.

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Emotional memory

• More emotionally events seem to be remembered more easily and vividly than less emotionally events

– Beginning or ending relationships– Arousing words / Neutral words– Events experienced by many people

simultaneously : tsunami , 9/11 terrorist attack

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Memory for emotional stimuli

Kevin Lavin and Elizabeth Phelps 1998

• Emotionally charged events are easier to remember– Tested participants’ ability to recall

– Arousing words : profanity & sexually explicit words– Neutral words : street , store

– They can recall immediately after they were presented

– Results : better memory for arousing words

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• Florin Dolcos and coworkers 2005– Tested participants’ ability to recognize emotional

and neutral pictures

– Memory test 1 year after they were initially presented

– Results : better memory for the emotional pictures


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(a) Immediately after reading a word(b) 1 years after viewing the pictures

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Emotional memory / Amydala

• Brain imaging : fMRI measured by Dolcos

– Amygdala activity was higher for the emotional words


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Emotional memory / Amygdala

• Neuropsychological study :Viewed a slide show about a boy and his

mother in which a boy is injured halfway through the show

• Participants : without brain damage– Enhanced memory for emotional part of story

• B.P. : damaged to amygdala– Not enhanced


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Amygdala

• Emotion improves memory

• Emotion enhance the process of consolidation


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Chapter summery 19

• Memory for emotional stimuli is generally enhanced compared to memory for neutral stimuli.

• The results of brain scanning and neuropsychological experiments indicate that the amygdala is involved in emotional memory.

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How do we retrieve information from LTM ?

Retrieval failure occur when the information is “in there” , but we can’t get it out.– Most of our failures of memory are failures of

retrieval

– Example : you’ve studied hard for an exam but can’t come up with the answer when you’re taking the exam, only to remember it later when the exam is over.

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Retrieval cues

• Cues that help us remember information stored in our memory

• Returning to a particular place stimulated memories associated with that place

• Location can serve as a retrieval cue

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Retrieval cues : location

• While I was in my office at home ,I had made a mental note to be sure to take the DVD on amnesia to school for my cognitive psychology class

• A short while later, as I was leaving the house, I had a nagging feeling that I was forgetting something, but I couldn’t remember what it was.

• As soon as I got home, I remembered

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Angela’s experience• When I was 8 years old, both of my grandparents passed

away. Their house was sold, and that chapter of my life was closed. Since then I can remember general things about being there as a child, but not the details.

• One day I decided to go for a drive. I went to my grandparents’ old house and I pulled around to the alley and parked. As I sat there and stared at the house, the most amazing thing happened. I experienced a vivid recollection.

• All of a sudden, I was 8 years old again. I could see myself in the backyard, learning to ride a bike for the first time. I could see the inside of the house. I remembered exactly what every detail looked like. I could even remember the distinct smell. So many times I tried to remember these things, but never so vividly did I remember such detail.

Retrieval cues : location

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Retrieval cues

• That are provided by returning to the location where memories were initially formed.

• Hearing the particular song can bring back memories for events you might not thought about for years

• A musty smell like the stairwell of my grandparents’ house that used to climb

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Cued recall

• Endel Tulving and Zena Pearlstone 1966• Presented participants with a list of words

to remember• Free-recall group

– Pigeon, sparrow, chair, dresser, engineer, lawyer

• Cued-recall group– Birds : Pigeon, sparrow– Furniture : chair, dresser– Professions : engineer, lawyer

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Endel Tulving and Zena Pearlstone 1966

For the memory test,

• Participants in the free-recall group were asked to write down as many as possible.

• Participants in the cued-recall group were also asked to recall the words, but were provided with the names of the categories : birds , furniture, professions

Cued recall

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Conclusion : the retrieval cues aid memory

• Free-recall gr. : Recall 40%

• Cued-recall gr. : Recall 75%

Cued recall

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Power of retrieval cues

Timo Mantyla 1986

• He presented his participants with a list of 600 nouns,

• such as : banana , freedom , tree

• During learning, the participants were told to write down three words they associated with each noun

• Banana : yellow , bunches , edible

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Timo Mantyla 1986

• When the participants took a surprise memory test,

• They were presented with the three words they had created and were asked to produce the original word,

• They were able to remember 90% of the 600 words

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Timo Mantyla 1986

• Compared to another groups1. During learning : created cues for “banana”

own cues provided in test

2. During learning : saw “banana” and cues created by someone else other person’s cues provided in test

3. Didn’t participate in learning other person’s cues provided in test

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• Timo Mantyla 1986

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Timo Mantyla 1986

• Conclusions : – Retrieval cues ( the 3 words ) provide

extremely effective information for retrieving memories,

– but that the retrieval cues were more effective when they were created by the person whose memory was being tested

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Chapter summery 20

• Retrieving LTM is aided by retrieval cues.

• This has been determined by cues- recall experiments and experiments and experiments in which participants created retrieval cues that later helped them retrieve memories.

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Encoding specificity

• Memory is better when a cue that was associated with an event is reinstated & when the event is to be remembered

– Encoding

– Retrieval

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D.R. Godden and Alan Baddeley’s 1975

“diving experiment”

• On land studying a list of words group

• Underwater studying a list of words group– Each ½ of both groups were tested for recall

on land– Each ½ of both groups were tested for recall

underwater

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“diving experiment”

The best recall occurred when encoding and retrieval occurred in the same environment

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Harry Grant and coworkers 1998Studying experiment• Participants read an article on psycho

immunology while wearing headphones.– Silent condition group– Noisy condition group

• Half of each : short-answer test on the article under silent condition

• Half of each : short-answer test on the article under noisy condition

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Studying experiment

Participants did better when the testing condition matched the study condition

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Chapter summery 21

• The principle of encoding specificity states that we learn information along with its context.

• Godden and Baddeley’s “diving experiment” and Grant’s studying experiment illustrate the effectiveness of encoding and retrieving information under the same conditions

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State-Dependent learning

• Internal state : mood or state of awareness

• Learning is associated with a particular internal state

Principle : memory will be better when a person’s state during retrieval matches his or her internal state during encoding

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Eric Eich and Janet Metcalfe 1989

• Memory is better when a person’s mood during retrieval matches his or her mood during encoding.Asking participants to think positive thoughts

while listening to “merry” music or depressing thoughts while listening to “melancholic” music

– Participants rated their mood while listening


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• When mood rating reach “very pleasant” or “very unpleasant”

• Encoding part of the experiment began

• Participants studied lists of words while in their positive or negative mood


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Eric Eich and Janet Metcalfe 1989• After the study session ended• Participants were told to return in 2 days

– The sad group stayed in the lab a little longer– Snacking on cookies and chatting with the

experimenter while happy music played in the background

– So they wouldn’t leave the laboratory in a bad mood


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2 days later– Participants returned– The same procedure was used to put them in

a positive or negative mood.

When they reach the mood

• They were given a memory test for the words they had studied 2 days earlier


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The best recall occurred when encoding and retrieval matched in same mood

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Chapter summery 22

• According to the principle of state-dependent learning, a person’s memory will be better when his or her internal state during retrieval matches the state during encoding.

• Eich’ s mood experiment supports this idea.

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What memory research tells us about studying ?

Ways of improving learning and memory

1. Elaborate and generate

2. Organize

3. Associate

4. Take breaks

5. Match learning and testing conditions

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Elaborate and Generate

Elaboration

• The step that transfer the material you are reading into LTM

– Maintenance rehearsal : read and reread

– Elaborative rehearsal : better transfer to LTM

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Research has shown that

• students who read a text with the idea of making up questions did as well on an exam as students who read a text with the idea of answering questions later ,

• and both groups did better than a group who did not create or answer questions


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Study technique : method of talking out loud

• Mahya Tavakkoli’ s method• My study technique is to talk out loud and explain

everything that I know. Sometimes when you read the material, you think “Yeah! I know this!” and move on.

• But when you get to the exam, you get struck! This is because the material is not in front of you.

• So by explaining everything out loud, it makes much more sense. It’s a good method to pretend that you’re the professor trying to teach a class of 500 students.


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• S.W. Peterson 1992– 82% of students highlight– Most of them do so while they are reading the

material for the first time

– Compared comprehension of both groups no difference between the performance of both groups when they were tested on the material


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Elaborative processing & generation effect

• Making up question• Answering question• Recheck correction of the answer to get

feedback • Mahya ’s method of “pretending you are

the professor”

– Beware of highlighting (automatic behaviour)


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Organize

Memory is better when the material is organized.

Organization • creates a framework that helps relate some

information to other information – Making “trees” – Image – Chunking

• makes the material more meaningful• Reduce the load on your memory

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Associate

Elaborative processing is associating what you are learning to what you already know

• Prior learning creates a structure on which to hang new information

• Creating imaging that link two things

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Take breaks

Study in a number of shorter sessions rather than trying to learn everything at once

• Memory is better when studying the material is broken into a

number of short sessions with breaks in between

than when studying occurs in one long session

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The advantage for short study sessions is called Distributed versus massed practice effect– It is difficult to maintain close attention to

material throughout a long study session– Studying after a break gives better feedback

about what you actually know. – Consolidation is enhanced during sleep

Take breaks

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Sleep effect

• Helps consolidation

• Restorative effect

– Improves ability to concentrate and pay attention

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• Memory should be better when study (encoding) and testing (retrieval) conditions match as closely as possible.

– Encoding specificity

– State-dependence learning

Match learning and testing conditions

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Smith’s result

Research has shown that people remember material better

• when they have learned it in a number of different locations,

compared to spending the same amount of time studying in one location

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Match learning and testing conditions

Making up questions about the material helps encoding

Answering the questions, which involves retrieval, not only provides feedback about how well you know the material but helps achieve better encoding as well

This strengthened encoding then increases the likelihood that retrieval will be successful

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Chapter summery 23

Five memory principles that can be applied to studying are

1. Elaborate and generate

2. Organize

3. Associate

4. Take breaks

5. Match learning and test conditions

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Are memories ever Permanent ?

• Memory is initially fragile, so a

disrupting event that occurs shortly after a memory is formed can disrupt formation of memory

• Once consolidation has occurred, then the same disrupting event cannot affect the memory

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Conditioning

Conditioning :

• procedure in which pairing a neutral stimulus with a stimulus that elicits a response

• causes the neutral stimulus to elicit that response

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Conditioning

Pavlov’s experiment 1927

• He presented a ringing bell ( the neutral stimulus ) to a dog

• Followed by presentation of food ( which causes the dog to salivate )

• This pairing eventually caused the dog to salivate when it heard the bell

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Conditioning

• Stimulus (food) response (saliva)

• Stimulus + neutral stimulus (ringing bell) response

• Neutral stimulus + … response

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Fear conditioning

• Stimulus (unpleasant) response (avoid)

• Shock freeze

• Stimulus (shock) + neutral stimuli (tone) response (freeze)

• Neutral stimulus (tone) response (freeze)

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• The rat hears a tone – The rat receives a shock to its foot– The shock causes the rat to freeze in place

• Pairing : tone & shock

• The rat tested later– Neutral tone causes the fear response of

freezing

Fear conditioning

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Fear conditioning

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Karim Nader ’s experiments

• How injection of the chemical anisomycin would affect fear conditioning

Anisomycin : • ATB that inhibits protein synthesis, • which causes the structural changes at the

synapse that are responsible for the formation of new memories

Fear conditioning

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Effect on fear conditioning of injecting anisomycin

• Condition 1 : inject before consolidation

• Condition 2 : inject after consolidation

• Condition 3 : inject during reactivation

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1 : Immediate presentation of anisomycin

• Day1 : inject anisomycin + Initial condition (tone + shock) fear response in rat (freeze)– Anisomycin disrupts protein synthesis before

consolidation occur

• Day3 : tone condition no rat’s memory for shock-tone pairing rat does not freeze

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2 : Later presentation of anisomycin alone

• Day1 : shock-tone pairing condition fear response (freeze) consolidation : rat learn to fear tone

• Day2 : inject anisomycin 24 hours after that– No disruption of rat’s memory– Consolidation has occurred

• Day3 : tone rat freeze

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3 : Later presentation of anisomycin with the tone

• Day1 : shock-tone pairing condition fear response (freeze) consolidation : rat learn to fear tone

• Day2 : tone rat freeze reactivation + inject anisomycin eliminates the rat’s memory

• Day3 : tone rat has no memory rat does not freeze

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Karim Nader ’s experiments

Karim Nader injected the anisomycin under 3 different conditions :

1. Immediate presentation of anisomycin prevents conditioning

2. Later presentation of anisomycin alone has no effect (consolidation occurred)

3. Later presentation of anisomycin with the tone eliminates conditioning

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Reconsolidation

Learning consolidation learning reactivation : reconsolidation memory

• 1 : learning // no consolidation

• 2 : learning consolidation memory

• 3 : learning consolidation learning reactivation // no reconsolidation eliminates memory

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Updating memory

• Animal returns to the location of a food source – Reactivates the original memory

• Animal finds that the food has been moved to a new nearby location– New information updates the memory– Updated memory is then reconsolidation

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Updating memory

• Reconsolidation & reactivation occur when retrieved , provide an opportunity for reinforcing or updating memories

• Memory becomes to being changed or disrupted every time it is retrieved

• Memory becomes a more dynamic and adaptable process

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Chapter summery 24

• Recent research on memory, based largely on fear conditioning in rats, indicates that memories can become susceptible to disruption when they are reactivated by retrieval.

• After reactivation these memories must be reconsolidated.

• This process may be a mechanism for refining and updating memories.

1 forming memories in the brain : process of consolidation consolidation : transforms new memories...

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remote eventsforming

brain damagegraded amnesia

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fragile state

recent events

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