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Vision Sensory System The eye Exactly what we sense from our __________________________________ Perceptual System The brain How we put together what we sense into a __________________________________ The Visual Sensory System Light is made of waves __________________________________ Different colors have different wavelengths __________________________________ Different amplitudes lead to differences in brightness Visible spectrum __________________________________ ROY G BIV Short wavelengths are near __________________________________ Long wavelengths are near red and orange Properties of Light and Waves The color of an object is determined by its abilities across two dimensions __________________________________ __________________________________ Colors that are reflected are the colors that __________________________________ A red sweater is red because it __________________________________ wavelengths that we perceive as red Other wavelengths would be absorbed and __________________________________ as a color for this sweater Properties of Light and Waves Black is a color that __________________________________ all other colors ie. It is the absence of reflected color White is a color that __________________________________ all other colors ie. It is the presence of all colors prisms Properties of Light and Waves Refraction The __________________________________ of the waves Occurs in water Different substances _______________________________________ The eye Sclera __________________________________that protects the eye and gives it shape Cornea Protective covering for the eye Begins to __________________________________ and focus them Aqueous humor Fluid filled area behind the cornea Provides nutrients to the __________________________________ Parts of the eye Pupil __________________________________ in the center of the eye Controls the amount of light that enters Iris The __________________________________ that controls the __________________________________ of the pupil Lens Bends to __________________________________ onto the retina Accommodation The process of the __________________________________ to properly focus the image on our retina Vitreous humor Gives the eye its shape __________________________________ The vitreous humor your born with is what you still have Floaters Debris that gathers in the vitreous humor and __________________________________ onto the retina Retina Translates _____________________________________________________ our brain can process Concave Object on retina is translated __________________________________ __________________________________ Rods and cones Optic Disk/ __________________________________ Area in the retina where nerves and blood vessels exit the eye Forms a __________________________________ __________________________________ Area in center of retina Layers of the Retina Four main types of visual processing neurons Ganglion cell layer __________________________________ and bipolar cell layer __________________________________ cells Visual Sensory Neurons Photoreceptors __________________________________ Cones Rods and Cones Where a sensory signal (light waves) gets changed into electrical energy Process called __________________________________ Rods Sensitive to __________________________________ Most of them in periphery Cones Sensitive to __________________________________ Most of them in fovea Rods Contain __________________________________ 120 million in a human eye Responsible for night vision Very __________________________________to light Very poor __________________________________ Cones 6 million in the human eye Responsible for vision in bright light __________________________________ 3 different types with different pigments Cones Three different types Blue, __________________________________ __________________________________, medium Red, __________________________________ Horizontal Cells __________________________________ from the photoreceptors Transfer that information to __________________________________ cells Bipolar cells Receive input from __________________________________ cells and __________________________________ Transmit information to amacrine cells Contain receptive fields _______________________________________________________ organization Lateral inhibition Horizontal cells that are activated by light in the “__________________________________” area __________________________________the bipolar cell Amacrine Cells Respond to __________________________________ in the visual environment Connect bipolar cells, __________________________________ cells, and other amacrine cells Ganglion cells Receive input from __________________________________ and amacrine cells Same center-surround receptive fields found in bipolar cells On-center bipolar fields connect to __________________________________ganglion cells Off-center bipolar fields connect to __________________________________ganglion cells What do receptive fields do? On-center and off-center fields provide for greater __________________________________ Large __________________________________surfaces don’t activate the neurons as well as __________________________________surfaces with lines, cracks, and ends Types of Ganglion cells Three types P cells: Parvocellular M cells: Magnocellular Non P or M cells Pathway to the Brain __________________________________ Group of ganglion axons exit the eye __________________________________ (part of the tectum) __________________________________- Lateral Geniculate Nucleus Visual cortex- __________________________________ (MT) Contralateral organization Visual hemifields in space are __________________________________organized Not contralaterally organized by the eyes The Thalamus The __________________________________nucleus (LGN) 6 Layers: Keep much of the information seperated __________________________________ and __________________________________ information go to different layers Non P and M projections go between the other layers Information from each eye goes to __________________________________ Displays retinotopy Primary Visual Cortex Located in the __________________________________ (Occipital Lobe) Also referred to as Striate cortex Brodmann Area __________________________________ V1 Cortical organization of V1 Cells don’t like __________________________________! They like __________________________________ Retinotopically organized Simple cortical cells Respond to edges from a specific location __________________________________ cells Respond to edges from a larger area than simple cells Orientation selective Often __________________________________ selective Other properties of V1 Cortical __________________________________ (half of V1 is devoted to fovea) Cells often respond to input from either eye, but with a preferred eye (“ocular dominance”) Ocular dominance columns M & P pathways project to __________________________________ Response preferences are organized into columns (ocular dominance, orientation, visual field location) Other Visual Areas: V2, V3… Also __________________________________ organized __________________________________ encodes colors Visual Pathways 2 Main pathways __________________________________ stream Also called the “where” stream Processes where things are in space __________________________________ Stream Also called the “what” stream Processes what things are The “Where” Stream Contains MT (area V5) Visual __________________________________ Integrates with the “where” stream of the __________________________________ in the parietal lobe to construct a full picture of the environment The “What” Stream Contains the __________________________________ (FFA) Responsible for recognition of __________________________________ Much debated The FFA debate __________________________________ area Scientists argue that the FFA is not sensitive to faces, but instead is sensitive to identification of things that we can expertly identify We’ve all seen so many faces that we are effectively “__________________________________” __________________________________show increased activation when identifying various types of birds Greebles Face-like Train people about the __________________________________ and check their activation Problems of the visual system Nearsightedness Focuses image __________________________________ Can see close, not far Farsightedness Focuses image __________________________________ Can see far, not close Astigmatism __________________________________ cornea Color processing theories __________________________________ theory Trichromacy Found in the retina __________________________________ theory Red-green, blue-yellow, and black-white Input from one color inhibits the other color Found beyond the retina Evidence from afterimages
