WORKING MEMORY

Suggesting working memory capacity is getting smaller as we age

what is working memory?

• processes and structures involved in holding and using information in mind 

  • Often further incoming information that we use to help process 

  • Plays a large role in encoding, storage, and retrieval 

• Limited capacity 

• Storage and processing functions

• Coordinating functions

Example working memory tasks:

• Digit span forward (storage) 

  • Repeat digits in forward order

• Digit span backwards (processing) 

  • Repeat digits in reverse order

Example working memory task:

• Computational span: complete addition problems 

  • Ex. 5+6, 4+3, 7+2

• Question asks: what was the second number in each problem?

Working memory capacity hypotheses

• General primary functions show little decreases HOWEVER

• When there is complexity in these memory tasks → older adults do less well

• Aging is considered with a decline in the CAPACITY of working memory 

  • Ex. more age differences in backwards span vs forward span = more complexity in backwards span

Evidence: does the capacity of working memory change with age

• Wingfield, stine, aberdeen 1988

• Purpose

  • Test hypothesis that there is age declines in WM capacity

• Participants

  • Young and old, Cross sectional 

• Procedure

1. Digit span forward (storage) 

   1. Ex. 1, 5, 2, 7, 3

2. Simple word span (storage + word identification)

   1. Ex. table, rainbow, chair

3. Loaded word span (storage + word identification + language comprehension)

   1. Ex. Kim Campbell was the first woman Prime minister of Canada. True/False

• Results

  • Digit: equal results no age difference

  • Simple: young did better than old, but not by much

  • Loaded: young did better than old by almost double the words recalled

• Interpretation 

  • Older adults have difficulty with WM processing

    • Age differences increase with the number of cognitive operations required  

Evidence: adult age differences in working memory 

• Dobbs, rule, 1989

• Purpose

  • Test hypothesis that there is age decline in WM capacity 

• Participants

  • 30-39 (average 35), 40-49 (average 45), 50-59 (average 55), 60-69 (average 65), 70+ (average 75)

  • Cross sectional

• Procedure

  • Digit span forward (passive storage) 

  • Digit span backward (processing) 

  • Peterson-Peterson task (passive storage) 

    • 3 digits presental aurally

    • Retention intervals of 3, 6, 12s where participants performed distractor tasks

  • Working memory lag task (the most WM processing) 

    • Lag 0 (report digit just heard) 

    • Lag 1 (report digit prior to digit just heard) 

    • Lag 2 (report the digit two before the digit just heard) 

• Results 

  • Forward: age group effect, but not a regular pattern

  • Backward: no age group effect

  • Peterson-peterson: was retention interval effect, but no age group effect and no interaction 

  • Lag task: 

    • 0 → no difference 

    • 1 +2 → decreases in every age group, and large declines between groups

• Interpretation

  • Older adults are less able to manipulate and process than younger adults

  • Age plays less in role in passive storage aspects of memory

Updates

• What is meant by capacity? 

• Could more accounts for declines in “capacity”?

  • Declines in sensory processing

  • Declines in inhibition

  • Declines in speed of processing

Declines” in inhibition evidence: Top-Down suppression deficit underlies working memory impairment in normal aging 

• Gazzaley, Cooney, Rissman, D’Esposito, 2005

• Purpose: 

  • measured brain activation as a function of instruction to ignore or process scenes. Also measured WM

• Participants: 

  • Young and old, cross sectional design within subject manipulation 

• Procedure: 

  • 3 conditions (stimuli stayed same, instructions different)

  • 4 pictures, 800ms for each face/scene picture → 9s delay → 1s for response → measure activation in ignore and remember and compared to passive 

    • Ignore scenes (ignore scenes, remember faces)

    • Remember scenes (ignore faces, remember scenes)

    • Passive view (no memory instruction)

Results

Declines” in inhibition evidence: Top-Down suppression deficit underlies working memory impairment in normal aging 

• Gazzaley, Cooney, Rissman, D’Esposito, 2005

• Remember scenes:

  • Y and O both have activation of scene processing area (left parahippocampal region)

  • No big difference

• Ignore scenes: 

  • Y had less activation during the ignore condition than passive view

    • good at inhibition

  • O had same activation during ignore condition and passive view 

    • Were not inhibition

• Working memory performance:

  • O less accurate than Y

  • O who performed worst rated ignored stimuli as more familiar 

    • There is variability in high performing older adults vs low performing older adults 

  • Reduced activation in ignore scenes condition predicted memory for faces

  • Older adults who were statistically much worse than young adults are the low performing ones 

    • Reduced accuracy and slower reaction time for faces and scenes

    • Degree of reduced activation in ignore scene instruction → predicted memory for scenes 

      • Older adults who CAN suppress/inhibit → they are the ones who CAN ignore and recall correctly

• Interpretation: 

  • Age related WM capacity deficits result partially from impaired attentional processes