|
IMPLICIT
EXPLICIT
LEARNING |
After
serious head injury,
survivors may still
be able to learn
without awareness,
via different brain
structures
New
research gives hope
for innovative
rehabilitation
WASHINGTON —
Severe closed-head
injury (CHI), like
that caused in a car
accident, can impair
the ability for
purposeful learning,
for example in
school or on the
job. However, there
is cause for hope:
Psychologists have
evidence that
severe-CHI survivors
may still be able to
learn without
awareness that
they’re learning.
This kind of
learning, called
“implicit,” may be
supported by a
separate,
earlier-evolving
brain mechanism than
the “explicit” type.
These findings,
which are reported
in the January issue
of Neuropsychology,
may aid the effort
to remediate the
cognitive abilities
of CHI survivors,
who often are
impaired during
young adulthood. The
Centers for Disease
Control have
estimated that 5.3
million Americans, a
little more than two
percent of the U.S.
population,
currently live with
disabilities
resulting from CHI.
Neuropsychology is
published by the
American
Psychological
Association (APA).
Two Washington
State University
researchers studied
implicit perceptual
learning in 19
participants between
the ages of 15 and
55, at least one
year after they
sustained severe
closed-head
injuries, most of
them in motor
vehicle accidents
but some in falls of
greater than 10
feet. All had been
in a coma for at
least 24 hours.
Heather M. Nissley,
M.S., and Maureen
Schmitter-Edgecombe,
Ph.D., compared the
CHI survivors’
implicit perceptual
learning with that
of 19 non-injured
controls, to learn
whether the injured
participants
retained the
capacity to learn
without explicitly
intending to learn,
in the absence of
awareness. CHI has
long been known to
hurt explicit
learning. Here’s an
example of the
different types of
learning: In
implicit learning,
children normally
acquire and
understand the
complex rules of
grammar -- although
(even as adults),
they may not be able
to describe the
rules or how they
learned them. In
explicit learning,
they learn the parts
of speech in the
classroom.
The first to
study implicit
learning in CHI
using a perceptual
task, Nissley and
Schmitter-Edgecombe
asked participants
to identify the
location of a target
number -- 6 -- on a
computer screen, as
it moved in a
seemingly random
fashion around a
matrix of numbers.
Participants did not
know that the
target’s location
was actually
determined by an
underlying pattern
of relationships
between that
location and the
arrangement of other
numbers in the
display (a
“covariation
pattern”). Despite
slower search rates,
the CHI group’s
improvement in
locating the “6” was
consistent with that
of the control
group, demonstrating
that, like the
uninjured
participants, they
learned perceptual
information
implicitly --
without conscious
awareness. Plus,
they demonstrated
this implicit
learning even though
they were clearly
impaired on tests of
explicit learning
and memory.
The findings hold
two-fold interest.
First, they support
the idea that there
may be two different
neural mechanisms:
one for implicit and
another for explicit
learning. What’s
more, it also is
likely that implicit
learning is not a
single, unified
learning process and
that different
neural substrates
may support the
different types of
implicit learning --
abstract, motor and
perceptual. Some
have argued that the
brain areas
underlying implicit
learning developed
earlier in evolution
and thus are more
unchanging and
resilient across
individuals than
later-evolving
areas; this would
make implicit
learning more immune
to neurological
injury (as well as
to age and other
individual
differences such as
intelligence and
education).
Additionally, with
the ability to learn
implicitly, people
can acquire new
information about
their environment
without it demanding
the attention
required by explicit
learning.
Second, the
findings hold
promise for new
approaches to
remediation for
survivors of severe
closed-head injury.
Perhaps over time,
the authors
speculate, these
people could learn
to implicitly
associate stimulus
cues in their
environment with a
specific behavior or
outcome. For
example, they could
implicitly learn
(just because things
are arranged in a
certain way) to
associate looking in
or writing in a
memory notebook with
environmental cues
repeatedly presented
over time.
“Persons with CHI
generally perform
better on tasks that
require automatic as
opposed to
controlled, or
explicit,
processes,” says
Schmitter-Edgecombe,
“suggesting that
automatic processes
could be exploited
in remediation.” For
example, therapists
could “teach”
complex skills by
breaking them down
into sub-components
that can be learned
implicitly and/or
made automatic. More
research is needed,
especially in
rehabilitative and
real-world settings.
###
Article:
“Perceptually Based
Implicit Learning in
Severe Closed-Head
Injury Patients,”
Heather M. Nissley,
M.S., and Maureen
Schmitter-Edgecombe,
Ph.D., Washington
State University;
Neuropsychology,
Vol. 16, No. 1.
(Full text of the
article is available
from the APA Public
Affairs Office and
at
http://www.apa.org/journals/neu.html
after January 30,
2002)
Maureen Schmitter-Edgecombe
can be reached by
phone at
509-335-0170 or by
email at
schmitter-e@wsu.edu.
The American
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