Transcript March 6, 2006

Today
• Neuroimaging
• Dementia in aging—get some charts from
her lecture
• Ocular changes with aging—learn
hyperopia
Working Memory is the ability to maintain and
manipulate information over short periods of
time necessary to guide behavior
Mean Reaction Time (msec)
1000
800
20s-30s
50s-60s
600
70s-80s
400
200
ALONE
COUNTING
DIGIT SPAN
Task Condition
Structural brain changes with aging
changes in brain volume
young
old
STRUCTURAL
Magnetic Resonance Imaging
FUNCTIONAL
Positron Emission Tomography
YOUNG
OLD
YOUNG
UNDER
RECRUITMENT
YOUNG
OLD
ELDERLY
NON-SELECTIVE
RECRUITMENT
OVER
RECRUITMENT
Reaction Time (msec)
1500
1250
Old
Young
1000
750
500
2
6
2
Memory Load
6
FASTEST
YOUNG
OLD
SLOWEST
Summary
•
Age-related decline in selective cognitive processes
•
Functional MRI is a powerful method with excellent spatial
and temporal resolution to study the physiological basis of
cognitive decline in normal aging
•
Evidence for selective prefrontal cortical dysfunction
(I.e. under-recruitment) with normal aging
•
Possible neural as well as behavioral compensation
Questions
• What is fMRI? What is it used for and how
does it work?
• What area of the brain has been shown to
have change in older people?
AGING OF THE NERVOUS SYSTEM—FUNCTIONAL
CHANGES
Again, in the normal aging brain the changes are relatively few. However impaired function and
increased pathology do occur.
Major functional deficits/ pathologies involve:
Motility (e.g. Parkinson’s Disease)
Senses and communication
Cognition (e.g. dementias)
Affect and mood (e.g. depression)
Blood circulation (stroke, multi-infarct dementia)
Parkinson’s Disease: Chapter 8, pp. 110-113
Dementias: Chapter 8, pp. 130-136
Dementia
• Dementia: global deterioration of intellectual and
cognitive function characterized by 5 major
mental functions:
–
–
–
–
–
–
Orientation
Memory
Intellect
Judgment
affect
(But clear consciousness)
Dementia (cont.)
• There are two types of dementia:
– Reversible
– Irreversible
T ABLE 8 - 7 Underlyin g and Rever sible
Cau se s of Dementia
D
E
M
E
N
T
I
A
Drugs
Emotional disorders
Met abolic or endocrine disorde rs
Eye and ear dysfunctions
Nutritional d eficienc ies
T umor and trauma
Infections
Arteriosclerotic complications
i.e., myocard ial inf arction,
stroke or heart f ailure
T ABLE 8 - 9 Chara cteri stic s of Multi - Infarct
Deme ntia
Hist ory of abrupt onset or stepwise deter ioration
Hist ory of transient ische mic at t ack or st roke
Presence of hy pertension or arrhythmia
Presence of any neurologic focal symptoms or signs
Amyloid Connections
• In Alzheimer’s, amyloids are made and
accumulate in brain tissues and cause
disturbances.
• Maybe these could be a point of
intervention to prevent progression of
alzheimers.
Characteristics of Multi Infarct
Dementia (table 8.9)
•
•
•
•
Transient ischemic attack or stroke
Hypertension, arrythmia
Focal neurological signs
Stepwise deterioration
Questions
• What are the causes of reversible dementia?
• What are the characteristics of multi-infarct
dementia?
• What are the major functional
deficits/pathologies in aging?
Aging of the Visual System
Definitions
• To look at a near source, the lens has to accommodate
(become more round); to look at a far source it doesn’t
have to accommodate.
• Myopia: nearsightedness because eyeball is too long or
lens is too strong. Corrected with concave lens.
• Hyperopia: farsightedness due to eye too short or lens is
not strong enough. Corrected with convex lens
• Presbyopia: loss of focusing power of lens because it has
stiffened—results in difficulty seeing objects close up
which necessitates lens to accommodate.
Aging of the Visual System
• Structural Changes (See handout given in class)
– Tear Film:
• Dry eyes or tearing
– Sclera:
• Fat deposits – yellowing
• Thinning – blueing
– Cornea
• Diameter does not change after age 1
• Shape changes
– Retina
• Photoreceptor density decreases; other layers become disordered
(rod density decreases with age, cone density remains)
• Illuminance decreases with age
– Lens
• Increased size and thickness
• Becomes more yellow
Aging of the Visual System
• Function
– Corneal and Lens
• Decreased accommodation power (loss of presbyopia: loss of
focusing power of lens because it has stiffened—results in
difficulty seeing objects close up.)
• Increased accommodation reflex latency
• Refractive error becomes more hyperopic with age
• Corneal sensitivity decreases
• Scatter increases
– Pupil
• Size decreases with age, particularly for dim light conditions.
Aging of the Visual System
– Retinal (MANY changes due to decreased amt of light reaching retina)
• Decreased critical flicker frequency
• Visual acuity declines
• Visual Field decreases
• Color vision changes
• Darkness adaptation is slowed
• Increased glare problems, longer time to recover from glare
• Decreased light reaches retina
• Visual acuity declines most with age when tested in low contrast with dim
light. The difference as compared to young people is very significant in this
case. (not as significant if tested with high contrast, bright light)
• Attentional visual field size decrease
• Stereopsis (close-up depth perception) shows large loss with age due to
difference in function of 2 eyes.
• Face recognition impaired
Other changes
• Words per minute decrease in reading
• Increased hyperopia: (farsightedness
because eye is short)
• Increased astigmatism (cornea of eye is
asymmetrically curved causing out of focus
vision)
Graph from handout—summary of
some main points
• Most change with age in:
–
–
–
–
acuity in glare 18x worse with aging
Next: glare recovery 15x
Next: attentional field 12x
Etc…
Aging of the Visual System
• Recommendation to Accommodate Problems: (she
didn’t discuss in too much detail, but good to
know)
–
–
–
–
–
–
–
Wear appropriate optical correction
Increase ambient light
Make lighting even and reduce glare
Improve contrast in critical areas
Avoid rapid changes in light level
Avoid Pastel
Allow more time