MemoryDr. Osama Refaat

Lecturer of Psychiatry, Cairo UniversityDirector of Training Department MOH

Definition

• Memory: The capacity to retain information over time

• Memory is one of the most important concepts in learning; if things are not remembered, no learning can take place

Physiology of Memory

• Memory trace represents a biochemical and electrophysiological change in brain

• Major areas:– Temporal lobe– Diencephalon– Mammillary bodies– Limbic system (amygdala, hippocampus, cingulate

gyrus)

• Major neurotransmitters:– Acetylcholine• Nucleus basalis of Mynert (Forebrain)

– Glutamate• NMDA receptors

Stages of Memory

• Encoding: the conversion of incoming information into a form that can be stored in memory (memory trace).

• Storage: maintaining information in memory over a period of time.

• Retrieval: the process of searching for stored information and bringing it to mind.

Basic Reasons for Forgetting

• Encoding Failure: information did not get into memory.

• Storage Failure: information has disappeared from memory; it is no longer in storage.

• Retrieval Failure: information is stored in memory but it cannot be located.

Major Theories of Forgetting

• Decay Theory: information in memory eventually disappears if it is not used. (“Use it or lose it.”)

• Interference Theory: information stays in memory permanently even if it is not used. Forgetting occurs because other things we have learned somehow prevent us from finding the information we want

• Repression: active forgetfulness

Experiment

You learn a list of 10 “nonsense syllables” (like XUG or MUW), then get a test on it 1, 2, 4 or 8 hours later (“retention interval”).

Does it matter if you are asleep or awake during this retention interval?

We are exposed to new information when we are awake but not when we are asleep.

Compare the amount recalled after 8 hours awake to the amount recalled after 8 hours asleep.

Your choices: (A) Recall will be higher after being asleep. (B) Recall will be higher after being awake. (C) Asleep = awake.Decay Theory predicts: ?Interference Theory predicts: ?

Decay Theory predicts: C

Interference Theory predicts: A

Sylla

ble

s R

eca

lled (

out

of

10)

0 5

10

Retention Interval

0 2 4 6 8

Asleep

Awake

Results Supported the Interference Theory

Types of Memory

3 types of memories:

– Sensory Memory

– Short-Term Memory

– Long-Term Memory

These memories differ in terms of 3 characteristics:

• Capacity: how many units of information can be held at one time.

• Duration of Storage: how long the information can be held.

• Reason for Forgetting: storage failure versus retrieval failure.

Long-Term Memory

• Relatively permanent storage of information

Declarative Memory:Information you can describe

Nondeclarative Memory:Information you cannot

describe

SemanticMemory:

General information

EpisodicMemory:Personally

experienced events

Skilledactions

Habits

Long-Term Memory Contains...

Long-Term Memory

• Capacity: virtually unlimited.

• Duration of Storage: up to a lifetime.

• Reason for forgetting: retrieval failure (e.g., interference).

Short-Term Memory(Working Memory)

• Def: Brief storage of information currently being used

• Capacity: 7 units, plus or minus 2– Chunking can increase the capacity of STM

• Duration of Storage: less than 30 seconds without rehearsal.

• Reason for forgetting: storage failure (e.g., decay, displacement).

Sensory Memory

• Def: Temporary storage of information• Capacity: large; contains

most details of sensory input. • Duration of Storage:

visual: 1/10 second; auditory: 2 seconds.• Reason for forgetting:

storage failure (e.g., decay).

Forgetting

Forgetting from Short-Term Memory: Decay or Displacement?

STM

LTM

After information enters STM, a copy may or may not be sent to LTM.

Soon, however, that information will disappear from STM.

Two processes could cause information to disappear from STM: decay and displacement.

Forgetting from Short-Term Memory: Decay or Displacement?

STM

LTM

Decay: information that is not rehearsed disappears as time passes.

Displacement: information being held in STM is pushed out by newly arriving information.

Displacement is most likely to occur when the capacity limit of STM has been reached (about 7 units of information).

Forgetting from Short-Term Memory: Decay or Displacement?

STM

LTM

Displacement is most likely to occur when the capacity limit of STM has been reached (about 7 units of information).

R D Q L T H JB

Forgetting from Short-Term Memory: Decay or Displacement?

STM

LTM

Displacement is most likely to occur when the capacity limit of STM has been reached (about 7 units of information).

B R D Q L T H

J

Types of Interference

• Retroactive Interference:– Recently learned information prevents recall of

earlier learned information.

• Proactive Interference:– Earlier learned information prevents recall of later

learned information

• When information is learnt:• RI:

• PI:

Target InfoInterferin

g Info

Target InfoInterferin

g Info

• When information is learnt:• RI:

• PI:

Lesson 1 Lesson 2

Lesson 2Lesson 1

Remembering

Suppose that you wanted to memorize the phone number of a restaurant: 562-7837. In terms of the model, your goal is to get this information into long-term memory.

Basic Sequence

Sensory Memory

Short-Term Memory

Long-Term Memory

Sensory Input

You look at a page of a phone book.

Scanning the page, you find the listing you want. This is a “sensory input” to the system. The first stop is sensory memory.

A copy is made in sensory memory of the visual patterns, 562-7837.

Basic Sequence

Sensory Memory

Short-Term Memory

Long-Term Memory

Sensory Input

Attention

Generally, just paying attention to something in sensory memory moves it to short-term memory. However, with verbal information, there is an extra step because short-term memory prefers to take information in an auditory form—a form you can hear.

This is called auditory encoding, the conversion of visual patterns to sounds. You do this when you “listen” to the sounds of these words on the screen.

Basic Sequence

Sensory Memory

Short-Term Memory

Long-Term Memory

Sensory Input

Attention

It involves pattern recognition. Visual patterns in sensory memory are compared to prototypes in long-term memory.

Sounds corresponding to the visual patterns are then located and copied into short-term memory.

Basic Sequence

Sensory Memory

Short-Term Memory

Long-Term Memory

Sensory Input

Attention

When you become aware of these sounds, you know they are in short-term memory. The process of auditory encoding has been completed.The link from LTM to STM illustrates the process of retrieval, a key intermediate step in memorization.

.

You have a new sequence of sounds in short-term memory: 562-7837. Your goal is to move this sequence into long-term memory.

Basic Sequence

Sensory Memory

Short-Term Memory

Long-Term Memory

Sensory Input

Attention

There are two strategies for moving information from STM to LTM: (1) repetition; (2) elaboration.

When you repeat (rehearse) information, two things happen:

Basic Sequence

Sensory Memory

Short-Term Memory

Long-Term Memory

Sensory Input

Attention

Repetition

1. You recirculate it in STM. Each time you do this, you “reset the clock” and get another few seconds before the information decays.

2. You increase the chances that the information will be copied into LTM. But this is an unreliable strategy.

Elaboration is much more effective. You retrieve related information from LTM and combine it with the information you are holding in STM.

Basic Sequence

Sensory Memory

Short-Term Memory

Long-Term Memory

Sensory Input

Attention

Elaboration

For example, you can use the letters that correspond to the digits on the phone dial and make a word out of the digits:

5 6 2 - 7 8 3 7

Basic Sequence

Sensory Memory

Short-Term Memory

Long-Term Memory

Sensory Input

Attention

Elaboration

L O B S T E R

Visualization works best. Try to come up with words that refer to objects you can picture in your “mind’s eye”.

Basic Sequence

Sensory Memory

Short-Term Memory

Long-Term Memory

Sensory Input

Attention

Elaboration

What you encode (enter into) long-term memory is the word, lobster, and the mental picture of a lobster. You also encode the rule, “Dial the digits that go with the letters.”

Basic Sequence

Sensory Memory

Short-Term Memory

Long-Term Memory

Sensory Input

Attention

Elaboration

It will help if you create a mental picture that links the lobster to the restaurant; maybe visualize a lobster going inside, like a customer.When it comes time to dial, the thought of the restaurant triggers the image of the lobster, which reminds you of your code word, “lobster”, and the rule: “Dial the digits that go with the letters.”

Testing Memory

• Bed side tests– Registration– Short term memory (digit span: the capacity to hear

and immediately repeat back a unfamiliar sequence of numbers)

– Long term memory• Specialized memory tests– WMS

• Part of cognitive battery– CAMCOG

Disorders of Memory

• Amnesia:– Anterograde– Retrograde– Global– Circumscribed

• Hypermnesia• Paramnesia:– Retrospective Falsification– Confabulation– Déjà vu (illusion of familiarity)– Jamais vu (illusion of unfamiliarity)