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The scope of preserved procedural memory in amnesia
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Advisor(s)
Abstract(s)
The finding that patients with amnesia retain the ability to
learn certain procedural skills has provided compelling
evidence of multiple memory systems in the human
brain, but the scope, defining features and ecological significance
of the preserved mnemonic abilities have not yet
been explored. Here, we tested the hypothesis that subjects
with amnesia would be able to learn and retain a broad
range of procedural skills, by examining their acquisition
and retention performance on five novel experimental
tasks. The tasks are based on real-world activities and
encompass a broad range of perceptual–motor demands:
(i) the weaving task involves weaving pieces of fabric from
woollen strings, using a manual weaver’s loom; (ii) the
geometric figures task consists of tracing geometric figures
with a stylus as they move horizontally across a touch
screen monitor; (iii) the control stick task involves tracking
a sequence of visual target locations using a joystick control;
(iv) the pouring task consists of pouring 200 ml of
water from a watering can into a series of graduated cylinders,
from a point 20 cm above the cylinders; and (v) the
spatial sequence task involves learning an ordered
sequence of pushing five spatially distributed buttons without
visual guidance. Ten chronic and stable amnesic subjects
(nine with bilateral medial temporal lobe damage due
to herpes simplex encephalitis or anoxia, and one with thalamic
stroke) and 25 matching normal comparison subjects
were tested on three occasions: initial learning at time 1;
retention at time 2 (24 h later); and retention at time
3 (2 months later). Despite impaired declarative memory
for the tasks, the amnesic subjects demonstrated acquisition
and retention of the five skills; their learning slopes
over repeated trials were comparable with those of comparison
subjects. These findings indicate that preserved
learning of complex perceptual–motor skills in patients
with amnesia is a robust phenomenon, and that it can be
demonstrated across a variety of conditions and perceptual–
motor demands. The comparability of the tasks
employed in this study with real-world activities highlights
the potential application of this memory dissociation in the
rehabilitation of patients with amnesia
Description
Keywords
procedural memory medial temporal lobes amnesia motor skill
Citation
Brain (2004), 127, 1853–1867
Publisher
Oxford University Press