motion

microstimulation experiment by Movshon and Newsome:

  • monkey shifted judgment to artificially stimulated direction

  • perceptual response was integration (vector sum)

  • integration required to solve “aperture problem”

perceiving moving objects:

  • aperture problem - observation of small portion of larger stimulus leads to misleading info. about direction of movement

    • activity of single V1 complex cell or MT cell does not provide accurate info about direction of movement

looking through apertures: our receptors have limited RFs

complex moving stimuli - gratings

  • present composite plaid and look for cells that correspond to conscious perception

  • V1- most cells tuned to hor. and vert. are excited, ones tuned to 45 deg. aren’t

  • MT- most cells tuned to hor. and vert. excited, sub-pop tuned to 45 that are excited

  • MST- excited to 45 but not hor. and vert.

rules that guide motion correspondence:

  • proximity

  • momentum- objects continue going in same direction

  • hysteresis- given interpretation tends to bias towards that interpretation

  • cross modal effects can bias correspondence

motion of intersections

  • must assign motion signals to object

  • some intersections are incidental (one object in front of other), so intersection does not represent an object

  • when this occurs, one cannot track the motion of the intersection- need object to assign motion to

induced motion:

  • if many things moving in one direction a stationary object may appear to move in the opposite direction

bio motion findings:

  • can identify actions, gender, self, friends, emotions