BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Visual categorization of simple stimuli  - Professor Joshua Solomo
 n\, Centre for Applied Vision Research\, City University
DTSTART:20190117T130000Z
DTEND:20190117T140000Z
UID:TALK115951@talks.cam.ac.uk
CONTACT:John Mollon
DESCRIPTION:Stimuli that vary along quantitative (or ‘prothetic’) cont
 inuua can be categorized on the basis of how much neural activity they eli
 cit. Loud and bright stimuli elicit more activity than quiet and dim stimu
 li. Stimuli that vary qualitatively (either along metathetic continuua or 
 between prothetic continuua) cannot be categorized on this basis. It is co
 nceivable that our brains contain homunculi who read tiny signs attached t
 o each fibre that describe their neurons’ preferred stimuli\, but contem
 porary theorists believe category information to be inherent in the cerebr
 al positions of active neurons. This helps explain why stimulus preference
 s vary systematically in the cortex\, forming multi-dimensional ‘maps’
  of position\, orientation\, and possibly other attributes such as spatial
  frequency\, binocular disparity\, and chromaticity. Nonetheless\, neurons
  and channels that can be distinguished on the basis of the stimuli they p
 refer are still called ‘labelled lines’. Various psychophysical method
 s exist for quantifying channel selectivity and deciding whether those cha
 nnels qualify as labelled lines. The focus of my talk will be a new model 
 for the 2 x 2FC paradigm\, in which observers must both detect and identif
 y (or categorize) modulations in a visual stimulus. Heretofore\, results f
 rom this paradigm have either been interpreted in lieu of any models (e.g.
  ‘labelled lines are implied when threshold for identification equals th
 reshold for detection’) or easily falsifiable high-threshold theories of
  detection. My new model is based on signal-detection theory\, and accommo
 dates a wide range of relationships between detection and identification. 
LOCATION:Kenneth Craik Room\, Craik-Marshall Building\, Downing Site
END:VEVENT
END:VCALENDAR