Defining a Link between Perceptual Learning and Attention
doi:10.1371/journal.pbio.0060221.g001
Defining a Link between Perceptual Learning and Attention
Yuko Yotsumoto 0
Takeo Watanabe 0
0 Yuko Yotsumoto and Takeo Watanabe are in the Department of Psychology, Boston University , Boston , Massachusetts, United States of America. Yuko Yotsumoto is also at the Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital , Charlestown , Massachusetts, United States of America; and the Department of Radiology, Harvard Medical School , Boston, Massachusetts , United States of America
EExperienced jewelers routinely classify diamonds that xperts show amazingly high perceptual skills. appear very similar to the uninitiated into different grades with high precision. Within a few seconds, airport baggage security officers can detect forbidden inconspicuous materials through x-ray images. Such feats are possible because the experts' eyes are trained through practice and experience. Long after most aspects of brain development have ceased, repeated exposures or trainings improve our perceptual/sensory abilities, and cause neural reorganizations in the brain. Such experience-induced improvement, called perceptual learning [1], and the accompanying neural changes, called neural plasticity [2-6], underlie not only our ability to master a trade but operate at a more fundamental level to help us make sense of the world. We are constantly exposed to an overwhelming amount of sensory signals, most of which are not noteworthy. To function normally in the world, we must react quickly and precisely to the important signals, while ignoring or discounting the less important, just as organisms must do in the natural environment to survive. By directing attention only to important signals or being repeatedly exposed to signals in an important context, our sensory systems learn to process important signals more efficiently than the less-important signals. Reflecting this fundamental role of perceptual learning, studies have been conducted to examine mechanisms of perceptual learning and neural plasticity with various kinds of tasks and stimuli by using behavioral measurements [2,3] and neurophysiological [7,8] and brain imaging techniques [9,10]. Perceptual learning and neural plasticity have also been studied in all the sensory modalities including vision, hearing [11], and touch perception [12].
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Models of Perceptual Learning
To explore the mechanism of perceptual learning, here we
focus on visual perceptual learning. Visual processing consists
of many different stages leading from eyes to cortical areas
for cognitive processes such as decision making (Figure
1). It is unlikely that all types of visual perceptual learning
involve the same cortical stage(s). The stage(s) in which
one type of visual perceptual learning occurs may depend
on many factors, including the learned visual feature such as
orientation and contrast, the type of tasks such as a detection
task or a discrimination task, and exposure to a feature
without a task. For instance, some types of visual perceptual
learning may only involve lower stages of visual processing,
such as V1, while other types of visual perceptual learning
may involve multiple stages of visual processing. Models
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of different mechanisms are proposed depending on the
stage(s) visual perceptual learning involves.
(A) Early stage, local network model: Adini et al. [13] and
Tsodyks, et al. [14] have proposed the model based on
perceptual learning of contrast discrimination (indicating
Copyright: 2008 Yotsumoto and Watanabe. This is an open-access article
distributed under the terms of the Creative Commons Attribution License, which
permits unrestricted use, distribution, and reproduction in any medium, provided
the original author and source are credited.
whether two contrast values are the same or different). In
their model, repeated presentation of a stimulus (a line
presented in the center) together with its surrounding
stimulus (lines presented around the central line) leads
to a change in the visual cortex as a result of interactions
between signals from the central and surrounding stimuli.
That is, for an observer to learn a stimulus in one location
(the central stimulus), the context in which the stimulus is
presented (surrounding stimuli) plays an important role. The
interactions can occur within the same cortex and therefore
we do not have to assume interactions between cortical areas
at different levels in the visual processing hierarchy. In this
model, the neural reorganization due to perceptual learning
can occur in a low-level cortex, including the primary visual
cortex (V1), which is the first visual cortex onto which visual
signals are projected. This model indicates the mechanism of
a type of perceptual learning that can involve only one level
of visual pr (...truncated)