2. Experiment design Research Methods Fall 2010 Tamás Bőhm

3. Elements of experiment design Question Method Stimulus Control Interpretation

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

5. Question Functional specialization of the cortex

6. Question Development of functions

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

8. Method Behavioral/psychophysics Electrophysiology Imaging Genetics …

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

10. Stimulus Brightness of the spots need to be controlled 1.Constant brightness (isoluminance): hard to achieve 2.Randomizing light intensity

11. Stimulus

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

13. Julesz Béla’s random dot stereograms (RDS)

14. Stimulus

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

16. Stimulus 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 Question: functional specialization Method: psychophysics, electrophysiology

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

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

19. Stimuli Huggins pitch: heard only binaurally http://www.parmly.luc.edu/parmly/

20. Stimuli Interaural time difference (ITD) is measured by a neural crosscorrelator Jeffress 1948; Licklider 1951

21. Stimuli Interaural time difference (ITD) calculated for each cochlear frequency channel: cue for both source segregation & pitch detection Jeffress 1948; Licklider 1951

22. Stimulus Binocular rivalry

23. Stimulus At which level of visual processing does this happen? –1980s: at low level Competition between the two eyes Reciprocal inhibition of monocular neurons Question: functional specialization Method: psychophysics

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

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

26. Stimuli

27. Stimulus At which level of visual processing does this happen? –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 Question: functional specialization Method: psychophysics

28. Stimulus Logothetis

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