Experiment design Research Methods Fall 2010 Tamás Bőhm.
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Transcript of Experiment design Research Methods Fall 2010 Tamás Bőhm.
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
• Functional specialization of the cortex
Question
• Development of functions
Question
• Operation of specific functions
What determines the brightness of a surface?
Method
• Behavioral/psychophysics
• Electrophysiology
• Imaging
• Genetics
• …
Stimulus
Ishihara plates:tests wavelength sensitivity(the tuning of retinal red and green cones)
Stimulus
Brightness of the spots need to be controlled1. Constant
brightness (isoluminance):hard to achieve
2. Randomizing light intensity
Stimulus
• Stereopsis (binocular depth perception): based on retinal disparity
• Can break camouflage
Stimulus
Stimulus
Julesz Béla’s random dot stereograms (RDS)
Stimulus
Stimulus
http://ruccs.rutgers.edu/%7Eikovacs/SandP/rds/rds.html
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 specializationMethod: psychophysics, electrophysiology
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
Stimulus
Take home message: use ‘clean’ stimuli
Stimulus
Binocular rivalry
Stimulus
At which level of visual processing does thishappen?– 1980s: at low level
• Competition between the two eyes• Reciprocal inhibition of monocular neurons
Question:functional specializationMethod: psychophysics
Stimuli
• Conventional rivalry inducing pair:eye-of-origin and stimulus coherence
Stimuli
• Patchwork rivalry stimulus (Kovács et al PNAS 1996): stimulus coherence only
Stimuli
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 specializationMethod: psychophysics
Stimulus
Logothetis
Stimulus
Take home message: get rid of extraneous factors in the stimuli