GICCS karni's talk
Georgetown Institute for Cognitive and Computational Sciences
Friday, October 18th
The Acquisition and Consolidation of Skills: Learning Related Plasticity
in the Adult Human Cortex
Dr. Avi Karni
Laboratory of Psychology & Psychopathology
National Institute of Mental Health
GICCS library. Research Building WP07. 12:00pm
Abstract
Behavioral and neurophysiological studies suggest that skill learning
(procedural, "how to", knowledge) is mediated by discrete,
experience-driven changes within the specific sensory or motor systems
subserving the performance of the trained task.
Behaviorally, adult skill learning has several characteristics which may
reflect the properties of basic neuronal mechanisms of plasticity that
subserve, throughout life, the acquisition and retention of skills: a)
Many instances of skill learning are specific for basic parameters of
the sensory, or motor, learning experience, suggesting discrete changes
in low-level representations as in developmental (critical period)
plasticity. E.g., in a visual "popout" figure-ground texture
discrimination task, improved performance does not generalize (transfer)
from one visual-field location to another, suggesting that learning
affects a level of processing wherein the retinotopic organization of
the visual input is still retained. Similarly, the effects of practice
on performing a short sequence of finger movements do not transfer to
the untrained hand, suggesting that a strongly lateralized
representation of the movement sequence is changing with learning. b)
Learning is not automatic - relevance and task related constraints have
to be met for learning to occur. Thus, repeated exposure per-se to an
appropriate visual input is insufficient to trigger long-term changes in
the adult visual system. Moreover, different neuronal representations of
a given visual input may be affected by different tasks ("gating"). c)
Skill learning has a distinct time-course: an initial, fast improvement
phase ("fast learning") is followed by a slowly evolving performance
gain ("slow learning") which takes several hours to become effective and
requires multiple daily practice-sessions to reach asymptote; The skill
is then retained for months and years. This time-course suggests a slow,
active process of long-term memory consolidation.
Functional MRI studies of primary motor cortex (M1) in adult human
subjects trained in a simple motor task, have shown changes in the
evoked cortical signals corresponding to fast learning. Furthermore,
this paradigm, as well as recent fMRI studies of primary visual cortex
in humans, and electrophysiological V1 recordings from a monkey, trained
in the performance of a visual figure-ground discrimination task,
indicate that with long-term training the neural representations of
critical parameters of the training experience (sequence of movements in
M1 in the motor task, and orientation-gradient dependent segmentation in
V1 in the visual task) expand. These findings support the notion of
slowly evolving experience-dependent plasticity in discrete, low-level
neural representations in the adult cortex and suggest that skill
learning while constrained by the functional architecture of the
processing system, can modify basic representations in it.
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