258 CHAPTER 6
defective—you can read data that are already on the hard drive, but you can’t store any new
information. As long as you are looking at the data in your open computer window (i.e.,
attending to it), you can access it, but as soon as you close that window (stop thinking about
it), the information is lost, because it was never transferred to the hard drive (long-term
memory). This makes for some very repetitive conversations, such as being told the same
story or being asked the same question numerous times in the space of a 20-minute conver-
sation. See Figure 6.10 for a comparison of retrograde and anterograde amnesia.
ALZHEIMER’S DISEASE Nearly 5.3 million Americans have Alzheimer ’s disease
( Alzheimer’s Association, 2015). It is the most common type of dementia found in adults
and the elderly, accounting for nearly 60 to 80 percent of all cases of dementia. It is estimated
that 1 out of 9 people over the age of 65 has Alzheimer ’s disease. It has also become the
sixth-leading cause of death in the United states and the fifth-leading cause of death in peo-
ple 65 years and older, with only heart disease and cancer responsible for more deaths (Alz-
heimer’s Association, 2015; Antuono et al., 2001; National Center for Health Statistics, 2015).
With Alzheimer ’s disease, the primary memory problem, at least in the beginning,
is anterograde amnesia. Memory loss may be rather mild at first but becomes more
severe over time, causing the person to become more and more forgetful about everyday
tasks. Eventually more dangerous forgetting occurs, such as taking extra doses of med-
ication or leaving something cooking on the stove unattended. As Alzheimer ’s disease
progresses, memories of the past seem to begin “erasing” as retrograde amnesia also
takes hold. It is a costly disease to care for, and caregivers often face severe emotional
and financial burdens in caring for a loved one who is slowly becoming a stranger.
What causes Alzheimer ’s disease is not completely understood. While it is normal
for the brain to begin to form beta-amyloid protein deposits (plaques) and for strands of
the protein tau to become twisted (“tangles”), people who suffer from Alzheimer’s disease
are found to have far more of these physical signs of an aging brain (Chen et al., 2012; Lim
et al., 2012). One of the neurotransmitters involved in the formation of memories in the hip-
pocampus is acetylcholine, and the neurons that produce this chemical break down in the
early stages of the disease (Martyn et al., 2012). While one early-onset form of Alzheimer’s
Figure 6.10 (a) Sometimes a blow to the head, such as might be sustained in an accident
like this one, can lead to the loss of memories from the time of the injury backwards—a loss of
recent memory which may be only a few minutes to several hours or days, or in some cases,
even years of the past. This is called retrograde amnesia, because “retro” means “relating to
the recent past. (b) Anterograde amnesia involves the loss of the ability to form new memories.
Memories of the distant past may still be intact, but newer memories such as the name of
the person you just met or whether you took your medication or not seem unable to “stick.”
That’s why a person with this type of amnesia (common in dementia) might not remember a
conversation that just took place or a visit from the day before.
Interactive
