Abnormal Psychology

706 CHAPTER 15

allows clinicians to note whether the individual’s dementia occurs with

behavioral disturbance or without behavioral disturbance. One woman

describes her husband’s recent behavioral disturbances:

My husband used to be such an easy-going, calm person. Now,

he suddenly lashes out at me and uses awful language. Last week, he

got angry when our daughter and her family came over and we sat

down to eat. I never know when it’s going to happen. He’s changed

so much—it scares me sometimes.

(National Institute on Aging, 2003, p. 47)

People with Alzheimer’s who exhibit behavioral disturbances

are more likely to have greater declines in cognitive functioning

and to need institutional care sooner than patients whose be-

havior causes less concern (Scarmeas et al., 2007). As noted in

Table 15.11, slightly more females than males develop this form of dementia, and

it accounts for progressively more cases of dementia in older age groups.

Brain Abnormalities Associated With Alzheimer’s Disease:

Neurofi brillary Tangles and Amyloid Plaques

Two brain abnormalities are associated with Alzheimer’s disease: neurofi brillary tan-

gles and amyloid plaques. In the following we consider each of these abnormalities.

The internal support structure of a neuron includes microtubules, which are tiny

hollow tubes that create tracks from the cell body to the end of the axon; nutrients

are distributed within the cell via these microtubules. A protein, called tau, helps

stabilize the structure of these tracks (see Figure 15.3). With Alzheimer’s disease, the

tau proteins become twisted together in what are called neurofi brillary tangles, and

these proteins no longer hold together the microtubules—which thereby disrupts

the neuron’s distribution system for nutrients. In addition, the collapse of this sup-

port structure prevents normal communication with other neurons. This process

may also contribute to the death of neurons. In fact, people with Alzheimer’s have

smaller brains than normal (Henneman et al., 2009).

The brains of people with Alzheimer’s disease are abnormal in another way—

they have amyloid plaques, which are fragments of proteins (one type of which

As people age beyond 65 years old, they are
increasingly likely to develop Alzheimer’s
disease. About half the cases in each age group
have moderate to severe cognitive impairment
(American Psychiatric Association, 2000).

Age (in years) Prevalence Among

Males

Prevalence Among

Females

65 0.6% 0.8%

85 11% 14%

90 21% 25%

95 36% 41%

Table 15.11 • Prevalence of Dementia of the

Alzheimer’s Type From Age 65 On

Figure 15.3

15.3 • Neurofi brillary Tangles in

Alzheimer’s Disease Tau proteins

stabilize the structure of a neuron from the

cell body through the end of the axon. With

Alzheimer’s disease, these proteins become

entangled, destroying the structure of the

neuron and disrupting its communication

with other neurons.

Source: National Institute of Aging.

Healthy neuron

Microtubules

Stabilizing

tau proteins

Diseased neuron

Disintegrating

microtubules

Disintegrating

microtubule

Microtubule subunits

fall apart

Tangled clump

of tau proteins

Neurofi brillary tangles
The mass created by tau proteins that
become twisted together and destroy the
microtubules, leaving the neuron without a
distribution system for nutrients.