BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Memento EPFL//
BEGIN:VEVENT
SUMMARY:The Role of V4 During Natural Vision
DTSTART:20121116T110000
DTEND:20121116T120000
DTSTAMP:20260428T043848Z
UID:0ebe3f1781d1204a797bfea71e3ec3b311394467a1f79a6386c41119
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Julien Mairal INRIA Grenoble\nThe functional organization 
 of area V4 in the mammalian ventral visual pathway is far from being well 
 understood. V4 is believed to play an important role in the recognition of
  shapes and objects and in visual attention\, but its complexity makes it 
 hard to analyze. Individual cells in V4 have been shown to exhibit a large
  diversity of preferences to visual stimuli characteristics\, including or
 ientation\, curvature\, motion\, color and texture.  Such observations we
 re for a large part obtained from electrophysiological and imaging studies
 \, when a subject (monkey or human) is shown a sequence of artificial stim
 uli during data acquisition. In our study\, we intend to go beyond such an
  approach and analyze a population of V4 neurons in naturalistic condition
 s. More precisely\, we record responses from V4 neurons to grayscale still
  natural images---that is\, discarding color and motion content. We propos
 e a new computational model for V4 that does not rely on any pre-defined i
 mage features but only on invariance and sparse coding principles. Our app
 roach is the first to achieve comparable prediction performance for V4 as 
 for V1 cells on responses to natural images. Our model is also interpretab
 le using sparse principal component analysis. In the neuron population obs
 erved and based on our computational model\, we discover as our main findi
 ng two groups of neurons: those selective to texture versus those selectiv
 e to contours. This supports the thesis that one primary role of V4 is to 
 extract objects from background in the visual field.  Moreover\, our stud
 y also confirms the diversity of V4 neurons. Among those selective to cont
 ours\, some of them are selective to orientation\, others to acute curvatu
 re features.\n\nThis is a joint work with Yuval Benjamini\, Ben Willmore\,
  Michael Oliver\, Jack Gallant and Bin Yu. All of this work was performed 
 at UC Berkeley.
LOCATION:INR113 http://plan.epfl.ch/?zoom=20&recenter_y=5863814.94355&rece
 nter_x=730548.85489&layerNodes=fonds\,batiments\,labels\,events_surface\,e
 vents_line\,events_label\,information\,parkings_publics\,arrets_metro\,eve
 nem
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR