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Experiment design

Experiment design. Research Methods Fall 2010 Tamás Bőhm. Elements of experiment design. Question Method Stimulus Control Interpretation. Question. Functional specialization of the cortex Development of functions (ontogenesis & phylogenesis) Operation of specific functions. Question.

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Experiment design

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  1. Experiment design Research Methods Fall 2010 Tamás Bőhm

  2. Elements of experiment design • Question • Method • Stimulus • Control • Interpretation

  3. Question • Functional specialization of the cortex • Development of functions(ontogenesis & phylogenesis) • Operation of specific functions

  4. Question • Functional specialization of the cortex

  5. Question • Development of functions

  6. Question • Operation of specific functions What determines the brightness of a surface?

  7. Method • Behavioral/psychophysics • Electrophysiology • Imaging • Genetics • …

  8. Stimulus Ishihara plates:tests wavelength sensitivity(the tuning of retinal red and green cones)

  9. Stimulus Brightness of the spots need to be controlled • Constant brightness (isoluminance):hard to achieve • Randomizing light intensity

  10. Stimulus

  11. Stimulus • Stereopsis (binocular depth perception): based on retinal disparity • Can break camouflage

  12. Stimulus Julesz Béla’s random dot stereograms (RDS)

  13. Stimulus

  14. Stimulus http://ruccs.rutgers.edu/%7Eikovacs/SandP/rds/rds.html

  15. Stimulus Question:functional specializationMethod: psychophysics, electrophysiology At which level of visual processing does stereopsis happen? • 1950s: at very high level (after figure-ground separation and form recognition) • Monocular form cues & contours are essential • Could not find neural substrates • Julesz: it must be early in processing! • No monocular cues on RDSs • Could find the corresponding binocular depth cells

  16. Stimulus response of a binocular depth cell • Hubel and Wiesel 1962 • Barlow, Blakemore and Pettigrew 1967 • Bishop 1969 • Gian Poggio 1984: disparity selective neurons in V1, V2, V3, V3a

  17. Stimulus Take home message: use ‘clean’ stimuli

  18. Stimulus Binocular rivalry

  19. Stimulus Question:functional specializationMethod: psychophysics At which level of visual processing does thishappen? • 1980s: at low level • Competition between the two eyes • Reciprocal inhibition of monocular neurons

  20. Stimuli • Conventional rivalry inducing pair:eye-of-origin and stimulus coherence

  21. Stimuli • Patchwork rivalry stimulus (Kovács et al PNAS 1996): stimulus coherence only

  22. Stimuli

  23. Stimulus Question:functional specializationMethod: psychophysics At which level of visual processing does thishappen? • 1980s: at low level • Competition between the two eyes • Reciprocal inhibition of monocular neurons • Kovács et al.: later in processing • Competition also between two coherent pictures • After the input layer of V1

  24. Stimulus Logothetis

  25. Take home message: get rid of extraneous factors in the stimuli Stimulus

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