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SUMMARY:Visual perceptual learning:  A new perspective - Professor Cong Yu
 \, Peking University
DTSTART:20150821T120000Z
DTEND:20150821T130000Z
UID:TALK60147@talks.cam.ac.uk
CONTACT:John Mollon
DESCRIPTION:For many years perceptual learning (PL) researchers are\nexcit
 ed by the observations that PL is specific to the trained retinal\nlocatio
 n and orientation\, and regard these specificities as\nindications of neur
 al plasticity in the early visual cortex. However\,\nwe have created a “
 double training” design to enable complete\nlearning transfer to untrain
 ed conditions\, suggesting that PL is\nmainly a cognitive learning process
  beyond the retinotopic visual\nareas.\n\nMore recently we studied why is 
 PL specific in the first place\, and\nwhat is really learned in PL. In dou
 ble training\, PL becomes\ntransferable if the subjects are exposed to the
  untrained location or\norientation through an irrelevant task\, indicatin
 g that learning\nspecificity may be to do with the untrained conditions. W
 e used a\ncontinuous flash suppression technique to create “bottom-up on
 ly”\nor “top-down only” exposure stimuli. We found that bottom-up\ne
 xposure of an untrained location or orientation\, or pure top-down\ninflue
 nces\, can both enable significant and sometimes complete\nlearning transf
 er. These results suggest that learning specificities\nmay result from neu
 ral under-activations at the untrained conditions\nthat receive insufficie
 nt bottom-up stimulation and/or top-down\nattention during training.\n\nIn
  addition\, we demonstrated that PL is a form of concept learning. We\nstu
 died orientation learning with orientation features defined by\neither lum
 inance gratings or symmetric dot patterns\, and motion\ndirection learning
  with first-order luminance stimuli and second-order\ncontrast stimuli. Ea
 ch pair of stimuli had distinctive physical\nproperties that are encoded b
 y different neuronal mechanisms. Using a\nvariation of the double training
  method\, we observed complete mutual\ntransfer of learning between gratin
 g and dot-pattern defined\norientations\, and between first- and second-or
 der motion directions.\nThese results indicate that what is learned in PL 
 is the abstract\nconcept of a trained visual feature\, such as orientation
  or motion\ndirection.
LOCATION:Kenneth Craik Room\, Craik-Marshall Building\, Downing Site
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