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