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

Executive function

Visuospatial skills

Memory

Language

Attention

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

4371506 -----> 4371506 MAINTAIN

4371506 -----> 6051734 MAINTAINand

MANIPULATE

Where’s theflag?

Is this supposedto be fun?

Should Ikick it?

200

400

600

800

1000

Mea

n R

eact

ion

Tim

e (m

sec)

Task Condition

ALONE COUNTING DIGIT SPAN

20s-30s

70s-80s

50s-60s

FUNCTIONALSTRUCTURAL

Magnetic Resonance Imaging Positron Emission Tomography

Structural brain changes with agingchanges in brain volume

young old

OTHER BRAIN REGIONS

FRONTAL

FUNCTIONALSTRUCTURAL

Magnetic Resonance Imaging Positron Emission Tomography

YOUNG

OLD

SPATIAL RESOLUTION

Primary visual cortex (V1) Ocular dominance columns

red = right eyeblue = left eye

TEMPORAL RESOLUTION

CUE DELAY RESPONSE

+ + +

QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

YOUNGUNDER

RECRUITMENT

ELDERLYOVER

RECRUITMENTNON-SELECTIVE RECRUITMENT

YOUNG

OLD

0

200

400

600

800

Rea

ctio

n Ti

me

(mse

c)2 Letters 6 Letters

FASTEST SLOWEST

YOUNG

Neural recruitment

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

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

Information processing speed

2 6 2 6500

750

1000

1250

1500

Young Old

Reac

tion

Tim

e (m

sec)

Memory Load

FASTEST SLOWEST

YOUNG

OLD

Neural recruitment

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

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

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

Information processing speed

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

Working memory task Functional MRI

EVXRC e

time