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Behrmann, M. & Plaut, D. C. (2013). Distributed circuits, not circumscribed
centers, mediate visual recognition. Trends in Cognitive Sciences, 17,
210-219.
Notes: Increasingly, the neural mechanisms that support visual cognition are
being conceptualized as a distributed but integrated system, as opposed to a
set of individual, specialized regions that each subserve a particular
visual behavior. Consequently, there is an emerging emphasis on
characterizing the functional, structural, and computa tional properties of
these broad networks. We present a novel theoretical perspective, which
elucidates the developmental emergence, computational properties, and
vulnerabilities of integrated circuits using face and word recognition as
model domains. Additionally, we suggest that, rather than being disparate
and independent, these neural circuits are overlapping and subject to the
same computational constraints. Specifically, we argue that both word and
face recognition rely on fine-grained visual representations but, by virtue
of pressure to couple visual and language areas and to keep connection
length short, the left hemisphere becomes more finely tuned for word
recognition and, consequently, the right hemisphere becomes more finely
tuned for face recognition. Thus, both hemispheres ultimately participate in
both forms of visual recognition, but their respective contributions are
asymmetrically weighted
Department of Psychology, Carnegie Mellon University, Pittsburgh, PA 15213,
USA. Electronic address: behrmann@cmu.edu
Behrmann, M. & Plaut, D. C. (2013). Bilateral Hemispheric Processing of
Words and Faces: Evidence from Word Impairments in Prosopagnosia and Face
Impairments in Pure Alexia. Cerebral Cortex.
Notes: Considerable research has supported the view that faces and words are
subserved by independent neural mechanisms located in the ventral visual
cortex in opposite hemispheres. On this view, right hemisphere ventral
lesions that impair face recognition (prosopagnosia) should leave word
recognition unaffected, and left hemisphere ventral lesions that impair word
recognition (pure alexia) should leave face recognition unaffected. The
current study shows that neither of these predictions was upheld. A series
of experiments characterizing speed and accuracy of word and face
recognition were conducted in 7 patients (4 pure alexic, 3 prosopagnosic)
and matched controls. Prosopagnosic patients revealed mild but reliable word
recognition deficits, and pure alexic patients demonstrated mild but
reliable face recognition deficits. The apparent comingling of face and word
mechanisms is unexpected from a domain-specific perspective, but follows
naturally as a consequence of an interactive, learning-based account in
which neural processes for both faces and words are the result of an
optimization procedure embodying specific computational principles and
constraints
Department of Psychology, Center for the Neural Basis of Cognition, Carnegie
Mellon University, Pittsburgh, PA 15213-3890, USA
Dundas, E. M., Plaut, D. C., & Behrmann, M. (2013). The joint development of
hemispheric lateralization for words and faces. Journal of Experimental
Psychology: General, 142, 348-358.
Notes: Consistent with long-standing findings from behavioral studies,
neuroimaging investigations have identified a region of the inferior
temporal cortex that, in adults, shows greater face selectivity in the right
than left hemisphere and, conversely, a region that shows greater word
selectivity in the left than right hemisphere. What has not been determined
is how this pattern of mature hemispheric specialization emerges over the
course of development. The present study examines the hemispheric
superiority for faces and words in children, young adolescents and adults in
a discrimination task in which stimuli are presented briefly in either
hemifield. Whereas adults showed the expected left and right visual field
superiority for face and word discrimination, respectively, the young
adolescents demonstrated only the right-field superiority for words and no
field superiority for faces. Although the children's overall accuracy was
lower than that of the older groups, like the young adolescents, they
exhibited a right visual field superiority for words but no field
superiority for faces. Interestingly, the emergence of face lateralization
was correlated with reading competence, measured on an independent
standardized test, after regressing out age, quantitative reasoning scores,
and face discrimination accuracy. Taken together, these findings suggest
that the hemispheric organization of face and word recognition do not
develop independently and that word lateralization, which emerges earlier,
may drive later face lateralization. A theoretical account in which
competition for visual representations unfolds over the course of
development is proposed to account for the findings. (PsycINFO Database
Record (c) 2013 APA, all rights reserved)
Department of Psychology, Carnegie Mellon University
Laszlo,
S. & Plaut, D. C. (2012). A neurally plausible Parallel Distributed
Processing model of Event-Related Potential word reading data. Brain and
Language, 120, 271-281.
Notes: The Parallel Distributed Processing (PDP) framework has significant
potential for producing models of cognitive tasks that approximate how the
brain performs the same tasks. To date, however, there has been relatively
little contact between PDP modeling and data from cognitive neuroscience. In
an attempt to advance the relationship between explicit, computational
models and physiological data collected during the performance of cognitive
tasks, we developed a PDP model of visual word recognition which simulates
key results from the ERP reading literature, while simultaneously being able
to successfully perform lexical decision-a benchmark task for reading
models. Simulations reveal that the model's success depends on the
implementation of several neurally plausible features in its architecture
which are sufficiently domain-general to be relevant to cognitive modeling
more generally
Department of Psychology, State University of New York, Binghamton, NY,
United States
Nestor, A., Behrmann, M., & Plaut, D. C. (2012). The Neural Basis of Visual
Word Form Processing: A Multivariate Investigation. Cerebral Cortex.
Notes: Current research on the neurobiological bases of reading points to
the privileged role of a ventral cortical network in visual word processing.
However, the properties of this network and, in particular, its selectivity
for orthographic stimuli such as words and pseudowords remain topics of
significant debate. Here, we approached this issue from a novel perspective
by applying pattern-based analyses to functional magnetic resonance imaging
data. Specifically, we examined whether, where and how, orthographic stimuli
elicit distinct patterns of activation in the human cortex. First, at the
category level, multivariate mapping found extensive sensitivity throughout
the ventral cortex for words relative to false-font strings. Secondly, at
the identity level, the multi-voxel pattern classification provided direct
evidence that different pseudowords are encoded by distinct neural patterns.
Thirdly, a comparison of pseudoword and face identification revealed that
both stimulus types exploit common neural resources within the ventral
cortical network. These results provide novel evidence regarding the
involvement of the left ventral cortex in orthographic stimulus processing
and shed light on its selectivity and discriminability profile. In
particular, our findings support the existence of sublexical orthographic
representations within the left ventral cortex while arguing for the
continuity of reading with other visual recognition skills
Center for the Neural Basis of Cognition, Carnegie Mellon University, 4400
Fifth Avenue, Pittsburgh, PA 15213, USA
Plaut,
D. C. & Behrmann, M. (2011). Complementary neural representations for faces
and words: A computational exploration. Cognitive Neuropsychology, 28,
251-275.
Notes: A key issue that continues to generate controversy concerns the
nature of the psychological, computational, and neural mechanisms that
support the visual recognition of objects such as faces and words. While
some researchers claim that visual recognition is accomplished by
category-specific modules dedicated to processing distinct object classes,
other researchers have argued for a more distributed system with only
partially specialized cortical regions. Considerable evidence from both
functional neuroimaging and neuropsychology would seem to favour the modular
view, and yet close examination of those data reveals rather graded patterns
of specialization that support a more distributed account. This paper
explores a theoretical middle ground in which the functional specialization
of brain regions arises from general principles and constraints on neural
representation and learning that operate throughout cortex but that
nonetheless have distinct implications for different classes of stimuli. The
account is supported by a computational simulation, in the form of an
artificial neural network, that illustrates how cooperative and competitive
interactions in the formation of neural representations for faces and words
account for both their shared and distinctive properties. We set out a
series of empirical predictions, which are also examined, and consider the
further implications of this account
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