Prof. Greg Francis1PSY 310: Sensory and Perceptual ProcessesPurdue UniversityOrientation tuningPSY 310Greg FrancisLecture 07Which one’s my daughter?Purdue UniversityHeading out of the eye Ganglion cells project to lateral geniculate nucleus(LGN)Prof. Greg Francis2PSY 310: Sensory and Perceptual ProcessesPurdue UniversityCells in LGN Similar to ganglion cells in retina Center-surround receptive fields Intricate parsing of inputs by ganglion cell types Revealed by staining the structure with various chemicalsPurdue UniversityLGN to cortex We’re going to skip LGN and jump right to visual cortexProf. Greg Francis3PSY 310: Sensory and Perceptual ProcessesPurdue UniversityLGN to cortex Projections are not random Cells in LGN project to particular places in V1Purdue UniversityLaminar structure Cortex has athickness, anddifferent cell typesexists at “layers” in thecortex Different types of cellsstain differentlyProf. Greg Francis4PSY 310: Sensory and Perceptual ProcessesPurdue UniversityStaining What you see depends on what kind of stain you usePurdue UniversityOculardominance Inputs fromdifferenteyes are(initially) keptseparateProf. Greg Francis5PSY 310: Sensory and Perceptual ProcessesPurdue UniversityCortex structure Many differentdefined “areas”of cortex V1 is theprimary visualarea Tip of theiceberg!Purdue UniversityRetinotopic maps Neighboringcells in cortexreceiveinformation fromneighboringregions of theretina There is a layoutof the retina incortex Biased towardthe foveaProf. Greg Francis6PSY 310: Sensory and Perceptual ProcessesPurdue UniversityCell responses Many cells inV1 aresensitive toparticularorientations ofedges Show movieSimpleCortCell250.mpg Noble prizewinning work!Purdue UniversityOrientation columns Cells in a region have similar orientation preferences Cells at different layers have the same orientation preferenceProf. Greg Francis7PSY 310: Sensory and Perceptual ProcessesPurdue UniversityReceptive fields The orientation sensitive cells are called “simple cells” They seem to just add up input in their receptive fields One side is positive, the other side is negative Many different sizesPurdue UniversityReceptive fields A simple like this will respond well to a vertical edge on the left But not to a vertical cell on the rightProf. Greg Francis8PSY 310: Sensory and Perceptual ProcessesPurdue UniversityReceptive fields Of course there are many different simple cells of thisorientation And their receptive field’s overlapPurdue UniversityReceptive fields Of course there are many different simple cells of thisorientation And their receptive field’s overlap A lot!Prof. Greg Francis9PSY 310: Sensory and Perceptual ProcessesPurdue UniversityCell response But at each position, there are also simple cells thatprefer the other kind of edgePurdue UniversityCell response But at each position, there are also simple cells thatprefer other orientationsProf. Greg Francis10PSY 310: Sensory and Perceptual ProcessesPurdue UniversityLayers We expand our layers idea to look at the responses fromorientation-sensitive cellsImageRetinaGanglion cellsPurdue UniversityLayers We expand our layers idea to look at the responses fromorientation-sensitive cells One layer for each type of receptive fieldImageRetinaGanglion cellsOrientationcellsProf. Greg Francis11PSY 310: Sensory and Perceptual ProcessesPurdue UniversityReceptive field So, if you have a bar grating as an imagePurdue UniversityReceptive field So, if you have a bar grating as an image One type of cell detects dark-to-bright edgesProf. Greg Francis12PSY 310: Sensory and Perceptual ProcessesPurdue UniversityReceptive field So, if you have a bar grating as an image Another type of cell detects bright-to-dark edgesPurdue UniversityReceptive field So, if you have a bar grating as an image Another type of cell detects horizontal edges In this image there are noneProf. Greg Francis13PSY 310: Sensory and Perceptual ProcessesPurdue UniversityReceptive field So, if you have a bar grating as an image Another type of cell detects edges at 45 degrees Notice an oriented cell responds to edges that areclose to it’s best edgePurdue UniversityReceptive field Repeat this process allover the visual field Many different orientationpreferences Many different sizes ofreceptive fields You start to see how thevisual system processesinformation in the scene A picture like this isrepresented amongmany differentorientation-sensitive cellsProf. Greg Francis14PSY 310: Sensory and Perceptual ProcessesPurdue UniversityReceptive field Repeat this process allover the visual field Many different orientationpreferences Many different sizes ofreceptive fields You start to see how thevisual system processesinformation in the scene A picture like this isrepresented amongmany differentorientation-sensitive cellsPurdue UniversityReceptive field Repeat this process allover the visual field Many different orientationpreferences Many different sizes ofreceptive fields You start to see how thevisual system processesinformation in the scene A picture like this isrepresented amongmany differentorientation-sensitive cellsProf. Greg Francis15PSY 310: Sensory and Perceptual ProcessesPurdue UniversityReceptive field Repeat this process allover the visual field Many different orientationpreferences Many different sizes ofreceptive fields You start to see how thevisual system processesinformation in the scene A picture like this isrepresented amongmany differentorientation-sensitive cellsPurdue UniversityBig issue The visual system seems parse out differentfeatures of the visual scene (e.g. orientatededges) We haven’t yet discussed other features Motion Color How does it all get put together into a singlescene? Why don’t I see oriented edges?Prof. Greg Francis16PSY 310: Sensory and Perceptual ProcessesPurdue UniversityBig issue Clearly visual cortex has an intricate structure tosupport all of these kinds of cells What does visual cortex do? What happens if it’s not there? You’ll be surprised! Movie Helen3.mpgPurdue UniversityConclusions Visual cortex Intricate structure Columns Orientation sensitive cells Split up visual scene Much, much more complicated than what wehave discussedProf. Greg