Neuroimaging studies of normal aging

• The effects of normal aging on cognition

• Neuroimaging as a scientific tool

• The physiological basis of cognitive changesin normal aging

Attention

Executive function

Visuospatial skills

Memory

Language

Working Memory is the ability to maintain and manipulate information over short periods of time necessary to guide behavior

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MANIPULATE

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Mea

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eact

ion

Tim

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sec)

Task Condition

70s-80s

50s-60s

20s-30s

ALONE COUNTING DIGIT SPAN

STRUCTURAL FUNCTIONAL

Magnetic Resonance Imaging Positron Emission Tomography

Structural brain changes with agingchanges in brain volume

young old

FRONTAL

OTHER BRAIN REGIONS

STRUCTURAL FUNCTIONAL

Magnetic Resonance Imaging Positron Emission Tomography

OLD

YOUNG

red = right eyeblue = left eye

Ocular dominance columns

Primary visual cortex (V1)

SPATIAL RESOLUTION

TEMPORAL RESOLUTION

+ + +

CUE DELAY RESPONSE

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YOUNG ELDERLYUNDER

RECRUITMENTOVER

RECRUITMENT

YOUNG

OLD

NON-SELECTIVE RECRUITMENT

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Rea

ctio

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ime

(mse

c)2 Letters 6 Letters

FASTEST SLOWEST

YOUNG

FAST ---------------------> SLOW

Neural recruitment

Information processing speed

LESS ---------------------> MORE

Memory Load2 6 2 6

500

750

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1250

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Young Old

Reaction Time (msec)

FASTEST SLOWEST

YOUNG

OLD

Neural recruitment

LESS ------------------------------------------------> MORE

FAST ---------------------> SLOW

Information processing speed

SLOW ---------------------> FASTYOUNG OLD

Summary

• Age-related decline in selective cognitive processes

• Functional MRI is a powerful method with excellent spatialand temporal resolution to study the physiological basis ofcognitive decline in normal aging

• Evidence for selective prefrontal cortical dysfunction(I.e. under-recruitment) with normal aging

• Possible neural as well as behavioral compensation

EVXRC e

time

Working memory task Functional MRI