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06 - Processing of visual motion

 

Topics addressed in the lecture:

  • motion as a fundamental perceptual dimension
  • motion as orientation in space-time
  • the anatomical localization of motion processing
  • the functional anatomy of area MT
  • the relationship between a stimulus, the neuronal response to it and the stimulus’ perception

Topics addressed in the seminar:

  • comparing psychometric and neurometric functions in a motion task
  • the relationship between the activity of single neurons in area MT and the perception of a moving stimulus
  • the effect of electrical microstimulation in area MT on perception

You should be able to answer the following questions after the lecture:

  • draw a space-time plot of a leftward motion
  • draw the tuning curve of a direction-selective cell, tuned to leftward motion
  • describe the topographic organization of area MT

You should be able to answer the following questions after the seminar:

  • what is meant by a neurometric curve and a psychometric curve (see Newsome et al.(1989))?
  • why is it interesting to compare these two curves?
  • describe the consequences of microstimulating area MT, as
  • determined by Salzmann et al. (1990)
  • what hypothesis is tested by this microstimulation experiment?

You should know the following terms and concepts after the lecture:

  • space-time plots for visual motion
  • direction-selectivity
  • tuning curve
  • Reichardt detector
  • dorsal pathway
  • extratstriate cortex
  • area MT

You should know the following terms and concepts after the seminar:

  • psychometric and neurometric curves
  • relationship between the effects of microstimulation and cortical topography

Learning objectives (Lernziele) - Lecture:

  • Visual motion is a fundamental perceptual dimension. This is evident from a number of independent observations.
  • Visual motion processing in primates is a high-performance system with obvious evolutionary benefits. It generates rich representations of the visual environment, even when only limited data are available (structure-from-motion, biological motion).
  • Simple (coherent, linear, 2D) visual motions are characterized by two parameters.
  • Motion can be thought of as orientation in space-time.
  • In primates neurons that respond selectively to visual motion do not occur before
    cortex. They usually encode motion direction through bell-shaped tuning curves.
  • In visual cortex one (the ‘dorsal’ or ‘where’ pathway) of two processing pathways is
    specialized for visual motion information. Extrastriate area MT has been identified as an area particularly specialized for linear motion processing. MT is retinotopically organized, but also shows a topography for motion direction and binocular disparity.
  • A fundamental question in neuroscience is to elucidate the causal link between a sensory stimulus in the environment and an organism’s perception of that stimulus. This has been particularly well investigated for area MT and visual motion perception (mostly covered in seminar).

Learning objectives (Lernziele) - Seminar:

  • A fundamental question in neuroscience is to elucidate the causal link between a sensory stimulus in the environment and an organism’s perception of that stimulus. This has been particularly well investigated for Area MT and visual motion perception.
  • Studies in area MT have revealed a very strong quantitative similarity between psychometric and neurometric curves for motion stimuli in this area.
  • The strongest evidence for a causal link between the neural activity in area MT and an organism’s perception comes from microstimulation experiments in MT of rhesus monkeys.
  • Circumstantial evidence comes from lesions studies and functional brain imaging.

Last update of this page: Dec 16, 2020