Learning & Memory
The type of memory impairments found in HD consist mostly of difficulties in learning
new information, and in retrieving acquired information, but not in storage of information. Problems occur in getting information
in and out, due to the slowed speed of processing and the poor organization of information.
Several studies have found that HD patients can demonstrate normal memory for
information if offered in a recognition format. If, rather than asking "can you tell me what time your doctor's
appointment is today?," one inquires "is your doctor's appointment at 10:00 or 11:00 today?," persons with HD can often answer
Similarly, if patients with HD are given a long list of words to learn and are required
to say the words back freely they perform poorly. But if they are given a list of words and asked to recognize which ones
were on the earlier list they demonstrate good memory.
It has been observed that persons with severe amnesia such as that associated
with Korsakoff's syndrome, herpes encephalitis, or Alzheimer's disease can experience defective explicit memory, such as for
names and dates, and intact implicit, or unconscious memory, such as the ability to tie one's shoes.
In contrast, persons with HD typically have impairments in skills that depend
on implicit memory. Driving, playing a musical instrument, or riding a bike are all motor memories that can be
considered implicit, or unconscious.