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CCS Seminar
Friday - October 12, 2007
12:00 noon
Physics Research Building - Room 595
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Professor Eric Schwartz
Professor of Cognitive & Neural Systems, Electrical & Computer 
Engineering and Anatomy & Neurobiology
Boston University
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"Computational Issues in Brain Imaging"

Magnetic resonance based human brain imaging studies require the 
experimental measurement, mathematical representation and digital 
manipulation of data that is embedded in highly convoluted cortical 
surfaces. In this talk, an overview of the computational issues 
associated with the measurement of functional architecture in the brain 
will be reviewed. Functional architecture studies are illustrated with 
the example of quasiconformal map complexes. These are physiological 
representations of the surface of the retina, relayed to the cortex in 
the form of multiple copies, or "maps" with shared boundary conditions, 
of a strongly non-linear, spatially warped retinal visual pattern. The 
two-dimensional dipole pattern, familiar from electrostatics, has 
provided a conjecture for the basic structure of these maps. Recently, 
this conjecture has been verified in both monkey and human brain in the 
form of the "wedge-dipole" model, using a variety of brain imaging 
methodologies. These experimental studies are dependent on access to 
maximally accurate, near-isometric surface flattening methods. Critical 
to these results are current methods for brain flattening, based on the 
computation of exact minimal geodesic paths on polyhedral surfaces, 
together with metric multi-dimensional scaling. Metric distortion in the 
range of 5-10% is achievable by full distance matrix flattening, with 
computation times (16 Gbyte 2Ghz Opteron) of roughly ten hours for (10k 
polygon) cortical surfaces spanning V1, V2 and V3, i.e. most of the 
occipital pole. These methods, which would greatly benefit from 
super-computer acceleration, have demonstrated that the detailed 
topographic structure of human and macaque visual cortex (in areas V1, 
V2 and V3) is very similar both across the two species, and across 
individuals in both species.

Recent publications describing this work can be found at 
http://eslab.bu.edu/publications/publications.php (articles and abstracts)

Supported by NIH/NIBIB EB1550



Cheryl Endicott
Administrative Assistant
Center for Computational Science
Boston University
3 Cummington Street
Boston, MA 02215
tel:617-358-1470
fax:617-358-2487
http://ccs.bu.edu

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