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SUMMARY:Is the homunculus `aware' of sensory adaptation? - Peggy Seriès (
 The University of Edinburgh)
DTSTART:20090609T150000Z
DTEND:20090609T160000Z
UID:TALK18724@talks.cam.ac.uk
CONTACT:Dr Jean-Pascal Pfister
DESCRIPTION:The properties of sensory neurons are not fixed.  They change 
 dynamically according to the spatial and temporal context and the task bei
 ng performed. Adaptation\, for example\, is known to result in a decrease 
 in response amplitude\, while attention enhances responses. How does the r
 est of the brain interpret these changes? Does the read-out adapt at the s
 ame time as the sensory neurons ?\n\nWe explore this question in the conte
 xt of sensory adaptation\, focusing on the examples of motion direction ad
 aptation and contrast adaptation.  In our framework\, perception is modele
 d as resulting from\nan encoder-decoder cascade. The encoder corresponds t
 o the response properties of a population of cortical neurons and changes 
 during adaptation. Different types of decoders are considered\, which are 
 either fixed and\n'unaware' of the adaptation state\, or which change dyna
 mically at the same time as the encoder\, being thus always optimal and 'a
 ware' of the\nadaptation state. Their predictions are compared with the ps
 ychophysical data for estimation and discrimination tasks.\n\nWe find that
  simple models of neural adaptation coupled with 'unaware' read-outs can a
 ccount for the main features of the psychophysical results.  We discuss th
 e significance of having 'unaware' read-outs\, and their relevance in othe
 r phenomena\, such as contextual interactions\, attention and perceptual l
 earning.\n\nWork in collaboration with E. P. Simoncelli and A. Stocker (NY
 U).
LOCATION:Cambridge University Engineering Department\, CBL Rm #438 (http:/
 /blg.eng.cam.ac.uk/t/bin/view/Public/Directions)
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