Symposia 98

Sunday April 5, 1998
8:30-10:30 AM

Chair

Michael C. Mozer, Ph.D.
University of Colorado
"Principles of computation in the brain"

Summary

Although the full potential of computational modeling in cognitive neuroscience has yet to be realized, models have helped us to understand the role of particular cortical areas in information processing and to understand how particular behavioral tasks are performed by the brain. Perhaps one reason for the limited impact of computational models is their specificity. Models tend to be narrow in scope, and modelers all too often tackle each new domain by setting aside their previous models and starting fresh. Without an effort to synthesize more basic principles, an outsider might easily be led to believe that computational modeling cannot be used to give us a big-picture view of information processing in the brain. This symposium will focus on computational principles of neocortical learning, dynamics, and control. Such principles should be general and systematic across the brain, clarifying various computational trade offs, such as response speed versus accuracy, innate versus learned knowledge, and rate of knowledge acquisition versus scope of generalization. These principles also allow for a unified explanation of disparate cognitive and neuroscientific data and a broad understanding of the nature of cortical information processing.

Participants

Robbie Jacobs, Ph.D.
University of Rochester
"Nature, nurture, and the development of functional specializations"

James L. McClelland, Ph.D.
Carnegie Mellon University
"Reopening the critical period: A Hebbian account of interventions that induce change in language perception"

Randall O'Reilly, Ph.D.
University of Colorado
"Principles for learning and processing in the cortex: Reconciling interactivity and generalization using competition and Hebbian learning"

David C. Plaut, Ph.D.
Carnegie Mellon University
"Systematicity and specialization in semantics"

Michael C. Mozer, Ph.D.
University of Colorado
"The temporal dynamics of information flow in cognition"

Sunday April 5, 1998
2:00-4:00 PM

Chair

Robert Stickgold, Ph.D.
Harvard Medical School
"State-dependent aspects of cognition"

Summary

Cognitive functioning in humans and animals is highly dependent on the brain/mind state of the subject. Different brain states are observed under normal conditions over the diurnal wake-sleep cycle and can be induced by psychoactive drugs. In both cases, brain state appears to be under the control of four subcortically mediated neuromodulatory systems ‹those of acetylcholine, norepinephrine, dopamine and serotonin. Shifts in the relative activities of these neuromodulatory systems produce not only uniquely distinct brain states, but specific states of consciousness as well. In this symposium, the interrelationships between wake-sleep states, neuromodulatory systems, and cognition are examined from both experimental and theoretical perspectives.

Participants

Pierre Maquet, Ph.D.
University of Liège
"Sleep and regional brain activations in humans"

Michael Hasselmo, Ph.D.
Harvard University
"Neuromodulators and state changes in waking and sleep"

Manfred Spitzer, Ph.D.
University of Ulm
"Neuromodulation of associative and working memory"

Robert Stickgold, Ph.D.
Harvard Medical School
"Sleep and cognition"

Monday, April 6, 1998
8:30-10:30 AM

Chair

George R. Mangun, Ph.D.
University of California, Davis
"Contributions of functional imaging to cognitive theory: What have we learned?"

Summary

Functional neuroimaging has generated tremendous excitement in the cognitive neuroscience community over the past 10 years, and this enthusiasm has reached new heights with the arrival of fMRI. The purpose of this symposium is to ask the hard question: "What important theoretical debates in cognition has functional imaging resolved, or significantly contributed to resolving?"

Participants

George R. Mangun, Ph.D.
University of California, Davis
"Introduction and overview: Functional imaging and human cognition ‹ Have our goals changed?"

Cathy Price, Ph.D.
Institute of Neurology, London
"Cognitive interactions: A new perspective on cognitive anatomy"

Gordon Shulman, Ph.D.
Washington University School of Medicine
"What kinds of questions can we ask about attention using neuroimaging: What have we learned, what might we learn?"

John Jonides, Ph.D.
University of Michigan
"Defining relationships between cognitive operations by analyzing overlapping brain systems: Attention and working memory"

Daphne Bavelier, Ph.D.
Georgetown University
"Imaging the plastic brain ‹ Viewing the functional anatomy of cognitive reorganization"

Monday, April 6, 1998
2:00-4:00 PM

Chair

Ursula Bellugi, Ph.D.
The Salk Institute for Biological Studies
"Bridging cognition, brain and genes: Evidence from genetically based syndromes"

Summary

This symposium represents the first fruits of a new Program Project that involves components across levels from Cognitive to Molecular Genetics. Williams syndrome is a rare genetic disorder (1:25,000) that presents with dissociations in higher cognitive functions both within and across domains. Individuals with Williams also have a characteristic personality. We present new results from brain and behavior research involving neurophysiology, neuromorphology, and brain cytoarchitectonics. We are also investigating the molecular genetic basis of the disorder, (loss of one copy of a small set of genes on chromosome 7 including elastin, lim1kinase. The symposium will focus on new research which begins to forge links across levels, from the neurobehavioral to molecular genetic.

Participants

Ursula Bellugi, Ph.D.
The Salk Institute for Biological Studies
"Fractionations in higher cogntive functions in Williams syndrome"

Zona C. Lai, Ph.D.
The Salk Institute for Biological Studies
"Emotional expression and perception in Williams syndrome"

Debra L. Mills, Ph.D.
University of California, San Diego
"Electrophysiological markers for Williams syndrome"

Michelle Harris-Collazo, Ph.D. and
Terry L. Jernigan, Ph.D.
University of California
"Neuromorphological characteristics of Williams syndrome"

Albert M. Galaburda, M.D.
Beth Israel Deaconess Medical Center and Harvard Medical School
"Brain cytoarchitectonic findings in Williams syndrome"

Julie R. Korenberg, Ph.D., M.D.
Cedars-Sinai Medical Center and UCLA School of Medicine
"The molecular genetic basis of Williams syndrome"

Monday April 6, 1998
5:30-7:30 PM

Chair

Raymond Klein, Ph.D.
Dalhousie University
"What the brain's neurons can tell the mind's models of mind"

Summary

The recent popularity of artificial neural network models of cognitive and behavioral processes derives in large measure from the promise they hold of providing a neural implementation of these processes (Hebb). To realize this promise and accelerate scientific progress we believe that artificial neural network models, which are already sensitive to the top-down constraint imposed by simulating performance, ought to reflect ‹ wherever possible ‹ the bottom-up constraint imposed by efforts to accurately reproduce the behavior of real processing units. Using visual orienting (both overt and covert, and its control by stimulation and the organism's intentions) as a model system (Posner) symposium presentations will illustrate how studying the behavior of individual neurons and assemblies of neurons during carefully constructed tasks can contribute to our understanding of fundamental cognitive constructs such as working memory, preparation, selection, and control. This work will be presented within the broader context of studies using other cognitive neuroscience methods (normal human performance, performance following brain damage, neuroimaging, etc.) with special emphasis on implications for neural network models, thus laying the foundation for fruitful interdisciplinary research.

Participants

Lawrence H. Snyder, Ph.D.
Washington University School of Medicine
"Task-specific processing of spatial information in posterior parietal cortex"

Earl K. Miller, Ph.D.
Massachusetts Institute of Technology
"Working memory as an active process in the prefrontal cortex"

Jeff Schall, Ph.D.
Vanderbilt University
"Visual selection and gaze control signals in frontal eye field"

Doug Munoz, Ph.D.
Queens University
"Mechanisms of visual fixation and motor preparation in the monkey superior colliculus"

Tuesday April 7, 1998
8:30-10:00 AM

Chair

Leslie Ungerleider, Ph.D.
National Institute of Mental Health
"Information storage in cortex: Representation of objects and words"

Summary

In this symposium evidence on the distributed nature of object and word representations will be presented. Keiji Tanaka will describe studies of nonhuman primates which show that object information is stored in columns of inferotemporal cortex, resulting in feature maps, rather than global object representations. Alex Martin will then discuss evidence showing that, in humans, object-feature information is stored as a network of discrete cortical regions. Within this network, information about different features is stored near the sensory and motor regions that were active when the information was acquired. The linkage between these semantic representations and the lexicon will be then be discussed by Alfonso Caramazza. Evidence will be presented suggesting that, similar to object feature information, the syntactic, orthographic, and phonological features of words are stored in discrete brain regions. Finally, the acquisition of semantic knowledge will be discussed by Faraneh Vargha-Khadem. Developmental studies will be described suggesting that learning context-free information is dependent on medial temporal lobe structures outside of the hippocampus.

Participants

Keiji Tanaka, Ph.D.
Riken Brain Science Institute
"Neuronal representation of visual object features in the monkey inferotemporal cortex"

Alex Martin, Ph.D.
National Institute of Mental Health
"Cortical representation of category-specific knowledge"

Alfonso Caramazza, Ph.D.
Harvard University
"Neurally based distinctions in the lexicon"

Faraneh Vargha-Khadem, Ph.D.
University College London Medical School
"Acquisition of knowledge after early-onset hippocampal pathology"

Tuesday April 7, 1998
2:00-4:00 PM

Chair

Karl Friston, MB, BS, MA, MRCPsych
Institute of Neurology
"Context-sensitive interactions in the brain"

Summary

Increasingly cognitive neuroscience depends on identifying the neural correlates of sensori-motor and cognitive processing. Concepts such as functional segregation have proved very useful in this regard. However the context-sensitive nature of brain responses renders the relationship between cognitive processing and its neuronal implementation more complicated than simpler frameworks might have predicted. The interaction between cognitive components, attentional modulation of sensory evoked responses, activity-dependent interactions between brain areas and behaviour-specific correlations are all clear examples of context-sensitive interactions in the brain. The proposed symposium will look at context-sensitive interactions in relation to how we characterize neuronal responses from four different perspective (using four different modalities); (i) computational neurobiology (simulated neuronal processes), (ii) dynamic correlations in electrophysiology (multiunit electrode recordings), (iii), effective connectivity in functional neuroimaging (fMRI) and (iv) context-dependent cognitive processing in memory (ERP).

Participants

Giulio Tononi, Ph.D.
The Neurosciences Institute
"Complexity and functional integration: A theoretical perspective"

Eilon Vaadia, Ph.D.
The Hebrew University of Jerusalem
Context-sensitive interactions and dynamic correlations"

Christian Buchel, Ph.D.
Wellcome Department of Cognitive Neurology
"Attentional modulation of effective connectivity as measured by fMRI"

Michael D. Rugg, Ph.D.
University of St Andrews
"Cognitive interactions during memory retrieval and their neural correlates"

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