Memory

Memory

What is memory? To a psychologist, memory is learning that has persisted over time, information that can be stored and retrieved.

How does memory work? One analogy would be to compare our memories to a computer. Information must be encoded (into brain), then it must be placed in storage (retained) and lastly it must be retrieved (get it back out).

Our memories do not work exactly like a computer. Our memories are more fragile and less literal. A computer processes speedily and in sequence while our brains are slower but does many tasks at one time.

Information processing models of memory

An early model of memory formation was developed in 1968 by Richard Atkinson and Richard Shiffrin. It is known as the three stage processing model of memory.

1. We first record to-be-remembered information as a short lived sensory memory

2. From there we process information into a short term memory bin, where we encode it through rehearsal

3. Finally, information moves into long term memory for later retrieval.

Models

A newer modified version of this model includes two important new concepts:

1. Some information skips the first two steps and is processed directly and automatically into long term memory, without conscious awareness

2. Working memory, is newer understanding of the second step. This newer info focuses on the active processing of information in the second stage. The brain cannot possibly process all the incoming stimuli at the same time, we focus our attention on certain stimuli (the novel or important). We process these incoming stimuli along with info retrieved from our long term memory, in a temporary working memory. Working memory associates new and old information and helps us solve problems.

Encoding

So how do we encode information? Automatic processing: the human brain

engages in parallel processing, doing many things at the same time.

Because your brain multi-tasks, it must resort to parallel processing. You process some things by automatic processing, without even thinking about it.

Automatic processing

We automatically process information about certain things. For example:

Space: encoding information based on where it is: Remembering information based on where you wrote it on a page

Time: while going through your day you automatically encode the sequence of your day: helps you remember where you left your coffee cup

Frequency: you without thinking remember the frequency of things that occur in your day

Well-learned information: you automatically recognize and process information that you know well: words on a billboard or sign

Effortful processing

Encoding of information through effort and attention. Effortful processing often produces accessible and durable memories.

Encoding can be aided through rehearsal. Rehearsal is conscious repetition.

Hermann Ebbinghaus was an early researcher in the field of verbal memory.

He studied his own learning and forgetting of novel verbal information.

Ebbinghaus

His experiment involved learning strings of unrelated letters. He would choose a list of the random syllables, read aloud and practice them, then test himself.

The day after learning the list, he would try to recall the syllables. But he could recall very few of them. Were they forgotten?

Ebbinghaus continued. He would change the number of times he rehearsed the list and then measure the time it took him to relearn it the next day.

He discovered that the more repetitions on day one, the shorter the relearning time on day 2.

Effortful Processing

From Ebbinghaus, we get one of the simple principles of effortful processing: The amount remembered depends on the time spent learning.

For novel verbal information, rehearsal , effortful processing, does improve memory performance.

Effortful processing

Spacing effect: We retain information better when our rehearsal is spaced out over time. Many studies have shown that spacing learning times is beneficial.

Massed practice can produce quick learning but distributed study time produces better long term recall.

Henry Bahrick(1993) conducted a study using himself and three members of his family. They practiced foreign language word translations for a set number of times but for varying intervals of time (14-56 days).

Effortful processing

What were the findings? The longer the space between practice sessions, the better the retention of the words up to 5 years later.

Practical application: spacing learning out is more beneficial. Reassessing retention is beneficial. Testing effect: testing can improve learning , not just assess it, Henry Roediger and Jeffrey Karpicke (2006).

Karpicke and Roediger(2008), gave study participants 40 Swahili words to learn. Students recalled the 40 words better if tested repeatedly than if they spent the same time restudying the words.

Spaced study and self-assessment beat cramming.

Effortful processing

Serial position effect: our tendency to recall best the first and last items in a list.

Serial position effect shows the benefits of rehearsal. We often remember things at the end of a list (recency effect), if we are asked to recall them soon after hearing them. This is probably because they are still in our working memory. But after a delay, we can best remember the things at the beginning of the list(primacy effect).

Effortful processing methods

We process information by either encoding its meaning, encoding its image or mentally organizing it.

When processing verbal information, we usually encode by its meaning. We associate it with what we already know or imagine. Context and experience become very important in this scenario.

What type of encoding produces the best memory of verbal information?

Encoding of verbal information

Visual encoding of information is the encoding of picture images.

Acoustic encoding is the encoding of the sound, especially the sound of words.

Semantic encoding is the encoding of meaning, including the meaning of words.

Each of these methods has its own brain system and each one can help you to remember verbal information.

Verbal information processing

In 1975, Fergus Craik and Endel Tulving compared visual, acoustic and semantic encoding. They flashed a word at people and then asked a question that required the participants to process the word at one of three levels.

1 visually (appearance of the letters) 2 acoustically (the sound of the word) 3 semantically (the meaning of the word)

Craik and Tulving

1. Is the word in capital letters? CHAIR 2. Does the word rhyme with train? brain 3. Would the word fit in the following

sentence? The man put the ____ on the table. Plate

Which type of processing would best prepare you to recognize the word at a later time?

Craik and Tulving

In their experiment, the deeper processing required for #3 led to better memory of the word than did the more shallow processing of #2 and especially #1.

Semantic processing aids memory if we have enough context to process the meaning of the content.

John Bransford and Marcia Johnson (1972) conducted an experiment on the importance of context to semantic encoding.

Bransford and Johnson

Try to remember the following passage.› The procedure is really quite simple. First you

arrange things into different groups. Of course, one pile may be sufficient depending on how much there is to do…After the procedure is completed one arranges the materials into different groups again. Then they can be put into their appropriate places. Eventually they will be used once more and the whole cycle will then have to be repeated. However, that is part of life.

Bransford and Johnson

In the study, when participants heard the passage without meaningful context, most could remember very little of it.

When told that the passage described washing clothes, they remembered much more of it.

The conclusion: processing a word through semantic encoding produces better recognition later than does shallow processing (visual or acoustic).

Encoding

Ebbinghaus concluded from his own experimentation that learning meaningful information required one-tenth of the effort that learning nonsense information did.

Point to remember: The amount remembered depends both on the time spent learning and on your making it meaningful.

Visual encoding

Visual encoding begins at our earliest memories primarily because we lack words and must rely on images.

Visual encoding does help with the memory of concrete nouns, especially when incorporated with semantic encoding.

Our memories of experiences is often inaccurate because of the vividness of visual imagery. This can lead us to remember the best or worst moment of an experience, instead of the overall event. It is a phenomenon called rosy retrospection. We have a tendency to recollect the high points of an experience.

Visual encoding

Mnemonic devices have visual imagery at the center. The ancient Greeks used such devices to help them memorize long passages and speeches.

Common mnemonic devices are the first letter approach, substitution technique, the peg word system and the method of loci.

First letter approach: Roy G. Biv Substitution technique: replace numbers with letters, as in when

business phone numbers spell a word The peg word system requires memorizing a jingle and then using it

as a memory tool Method of loci: memory palace, uses a memory of a particular place

which is composed of a number of discrete loci. The loci are then as memory locations for objects to be remembered. The objects are linked to the loci with a visual image. To remember them all one must do is mentally stroll through the loci.

Visual encoding

Mnemonic devices can help organize material for later retrieval.

Chunking is also a helpful method to improve memory. Information is easier to remember when organized into meaningful chunks.

Nickels Seven Any In Stitch Don’t Saves Ago A Score Time And Nine Wooden Four Years Take

Visual encoding

Don’t take any wooden nickels Four score and seven years ago A stitch in time saves nine Chunking can also be used to learn and recall

new information. Examples: Roy G. Biv, HOMES or My very

educated mother just served us nachos. People also chunk information into hierarchies,

as they become more knowledgeable about the topic. The hierarchies are organized around broad topics, subprinciples and specific content.

Hierarchies

Hierarchies help us to retrieve information efficiently.

Gordon Bower ,et al (1969) demonstrated this in a study. They presented words either randomly or grouped into categories. When the words were organized into groups the recall was two to three times better.

Storage: Sensory Memory

Sensory memory: there are two types of sensory memory.

Iconic memory: a momentary sensory memory of visual stimuli; a photographic or picture image memory lasting no more than a few tenths of a second

Echoic memory: a momentary sensory memory of auditory stimuli; if attention is elsewhere, sounds and words can still be recalled within 3 or 4 seconds

Sensory memory

In a 1960 study, George Sperling showed participants three rows of three letters for about one-twentieth of a second. After the letters disappeared the participants could only remember about half of them.

Sperling believed that the letters could only be remembered momentarily but that all of them were remembered. The problem was timing. He devised a method to account for that. After the numbers disappeared, he would sound a tone. High for the top row, medium for the middle tone and low for the bottom row. By sounding different tones he could prove that the numbers were all remembered. All nine letters were momentarily available for recall.

Sperling

Sperling’s experiment revealed that we do have a quick and fleeting photographic memory(iconic memory)

For a brief space of time (tenths of a second), our eyes register an exact visual representation of the scene and we can recall it with amazing detail. But if the recall was delayed by more than half a second the recall was again cut in half.

Echoic memory

Echoic memory holds auditory stimuli for three to four seconds.

This explains why the following occurs: You are sitting in class, not paying attention. The teacher realizing that you are not paying attention calls on you. What did I just say? When you are able to answer the teacher, this is your echoic memory. If the teacher waits about 10 seconds before calling on you, you may not know what she said.

Working/Short term memory

Without rehearsal most information leaves our brains within a short period of time. To retain information our working memory must encode or rehearse the information.

Peterson and Peterson tested the theory of how quickly will a short term memory disappear in 1959. Participants were asked to remember a three consonant combination. To prevent rehearsal, they were then asked to count backwards from 100 by threes. After 3 seconds, the participants recall was only about 50%; after 12 seconds, they seldom remembered them at all.

Short term memory

Short term recall is: Slightly better for random digits than

random letters Slightly better for what we hear than see Covers about as many words as you can

speak in 2 seconds More spoken words that signed words Basic Principle: At any given moment,

we can consciously process only a very limited amount of information.

Storage of memories in the brain

How do we store memories in the brain? For many years, researchers believed that your whole life

was in your brain. They believed this because of flashbacks triggered from brain stimulation during surgical procedures.

Loftus and Loftus analyzed this in 1980, and discovered that the flashbacks seemed to have been invented not relived.

In 1950, Karl Lashley, demonstrated that memories do not live in one discrete location but are located in a variety of places throughout the brain. He trained rats to complete a maze, then he excised different parts of their cortex. He then retested them. Regardless of which small piece he had removed, the rats retained some memory of how to complete the maze.

Synaptic changes

We know that experience changes the brain’s neural pathways. Increased activity causes a pathway to strengthen or form new neural connections.

We know that during learning, certain neurons will send out larger amounts of certain neurotransmitters. These synapses become more efficient at transmitting messages.

Synaptic changes

Increased synaptic efficiency leads to more efficient neural circuits. In experiments, rapidly stimulating memory circuit connections has been shown to increase the sensitivity of the memory circuit connections for hours, days, sometimes even for weeks.

The sending neuron now needs less prompting to release its neurotransmitters and the receiving neuron’s receptor sites may increase.

This strengthening is called LTP or long term potentiation. LTP provides a basis for learning and remembering associations.

LTP

How do we know that LTP is a physical basis for memory?

Drugs that block LTP interfere with learning (Lynch & Staubli, 1991)

Mutant mice engineered to lack an enzyme needed for LTP can’t learn their way out of a maze (Silva, et al, 1992)

Rats given a drug that enhances LTP will learn a maze with half the mistakes usually made (Service, 1994)

Injecting rats with a chemical that blocks the preservation of LTP erases recent learning (Pastalkova, et al, 2006)

LTP and medications

One possibility is to create drugs that boost the production of CREB, a protein that can switch genes on and off. Here’s how it might work:

1) genes code the production of protein molecules 2) with repeated neural firing, genes produce synapse

strengthening proteins 3) this enables LTP 4) CREB might lead to increased production of proteins

that reshape and strengthen synapses and help to consolidate ST memory into LT memory

Studies with sea slugs, mice and fruit flies have shown that increased CREB production can lead to enhanced memory.

LTP and medications

A different approach is also developing drugs that boost glutamate. Glutamate is a neurotransmitter that enhances synaptic communication (LTP). The problem with glutamate is the potential for side effects (migraines, seizures).

With all drug therapies, comes the potential for creating minds so cluttered with the trivial that we can no longer think.

LTP

We know that adequate sleep enhances memory.

We also know that ECT, after LTP has occurred does not disrupt memory. However, new memories (no LTP) are wiped clean by ECT(electroconvulsive therapy).

Head injuries can do the same.

LTP and medications

There are currently companies working on pharmaceuticals to boost memory. They have a huge target population. Those with Alzheimer’s disease, dementia, mild cognitive disorders (which can become Alzheimer’s) and those that would just like to turn back time.

Assignment

In writing, discuss the implications of drug based memory enhancement. Be sure to address positives, negatives and ethical issues.

Due next class.

Stress hormones and memory

When we are excited or stressed our bodies produce stress hormones. These hormones make more glucose available to fuel brain activity, indicating to the brain that something important is happening. The amygdala will also boost activity and available proteins in the memory forming areas of the brain.

This an sear certain events in the brain while disrupting the memory for neutral events.

Emotions

Stronger emotions seem to create stronger memories. Memories of traumatic events seem to intrude over and over.

This make adaptive sense. These strong memories serve as a reminder to protect us and keep us alert to danger.

Weaker emotions seem to create weaker memories. Cahill in 1994 found that people given a drug that blocked stress hormones had more difficulty remembering details of a upsetting story.

Flashbulb memories

Flashbulb memories are clear memories of an emotionally significant event or moment

Flashbulb memories can be explained by the emotion-triggered hormonal changes that occur during the event.

Flashbulb memories are more authentic when we experience the event as opposed to hearing about it. Rehearsing, reliving and discussing the memory are more likely to lead to errors seeping into the memories.

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Explicit m

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Implicit memory: non-declarative memory Learning how to do something Implicit is usually impossible to explain and

involves skills we learn Without conscious recall Processed by brain areas (not hippocampus) like

the cerebellum Skills-motor and cognitive Classical conditioning

Explicit memory: declarative memory Explicit memories are usually easy to

explain and involves episodes we experience and facts we learn

With conscious recall Processed in the hippocampus Facts-general knowledge Personally experienced events

Studies of amnesia

H.M. : in 1953 had his hippocampus removed due to seizure disorder

Old memories intact No new memories

formed Could develop skills at

performance of tasks but did not remember tasks

Several researchers (Brenda Miller, Suzanne Corkin)

Jimmy : suffered a brain injury in 1945

All new memories stopped at that point

Studied by Oliver Sacks In the 1970’s believed that

Truman was president, no way we landed on the moon

Confused and distressed by mirror image of self

Like others can find a room but not tell you where it is, gets faster a skill activities but does not remember them

Hippocampus

Brain scans have shown that when we are recalling words (Squire, 1992) and autopsies of people with amnesia have shown that the hippocampus (a temporal lobe neural center, part of the limbic system) is responsible for laying down our new explicit memories of names, events and images.

Damage to the hippocampus

Kamil & Cheng, 2001 and Sherry & Vaccarino, 1989 studied the ability of chickadees to remember the location of their food caches. Chickadees and other birds store food in hundreds of places and then return to those places in the winter for food. If their hippocampus has been removed they cannot locate the food caches.

Hippocampus

The hippocampus is lateralized. (having one on each side of the brain)

Damage to one or the other seems to produce differing results.

For example; with left hippocampus damage, people have trouble with verbal information but have no difficulty with visual design or location information

With right hippocampus damage the problem is reversed.

Hippocampus

New research is working with the subregions of the hippocampus.

Zeineh et al(2003) one part is active as you learn faces with names

Maguire et al (2003)a different part is active when memory whizzes engage in spatial mnemonics

Maguire et al (2003) the rear area of the hippocampus grows in cab drivers who have been navigating London’s streets based on length of time

Hippocampus

The hippocampus is active during slow wave sleep, while memories are being processed.

The greater the hippocampus activity while sleeping (after a training exercise) the greater the next days recall. These memories are not permanently stored in the hippocampus, rather it acts as a loading dock where the brain registers and temporarily holds the days events, locations, smells and names. Then the memories shift to other locations for storage.

Tse, et al (2007) removed the hippocampus of rats 3 hours after they had learned the location of a tasty treat. The process was interrupted and the rats could not remember. No long term memory had been formed. The same procedure performed after 48 hours did not impact the formation of a long term memory.

Hippocampus and the brain

During sleep activity levels correlate between the hippocampus and the brain cortex. Researchers believe that this “dialogue” is the process of memories being consolidated and transferred into long term storage.

Once stored these memories activate various parts of the frontal and temporal lobes.

Cerebellum

The cerebellum plays a key role in forming and storing your implicit memories. Associations learned through classical conditioning are not made by people with a damaged cerebellum.

The cerebellum is likely involved in the learning of new skills.

Dual explicit-implicit memory system

Our dual system may explain infantile amnesia. The implicit memory handles the reactions and skills that you learn as a child and carry throughout your life. But you generally cannot anything (explicit) about your first three years.

Although you can remember a few things as a young child, most adults can no longer recall. This is partly because of the language issue, adults store and retrieve memories using the spoken word and non-speaking children have not yet learned these words and partly because the hippocampus is one of the last parts of the brain to mature.