Visual Perception Flashcards
What are photoreceptors?
Cells with light sensitive photopigments in outer segments
What are rods?
Cells that contain rhodopsin, respond in dim light and are not present in the fovea
What are cones?
Cells that are involved in colour vision and concentrated in the fovea
What are the three types of cones?
Long-wave, medium-wave, short-wave
What are retinal ganglion cells?
Cells involved in the last stage in retinal processing
What are the 2 types of retinal ganglion cells?
Large parasol ganglion cells and small midget ganglion cells
What is the receptive field of a retinal ganglion cell?
The part of the retina from which the cell receives input
Keffler (1953) measured single cell recordings of retinal ganglion cells; what did they find?
- no activity when light fills the entire receptive field
- excitation when light fills the centre
- inhibition when light fills the surrounding
What are the characteristics of retinal ganglion processing?
- poor at spotting gradual changes
- good at detecting sharp edges
- filters input for useful information
What are the 2 illusions showing the perceptual effects of retinal ganglion cells?
- Baumgartner (1960)’s Hermann grid
- Simultaneous contrast
What are the 3 layers of the lateral geniculate nucleus (LGN) and their functions?
- Magnocellular: detection of movement and flicker
- Parvocellular: detection of colour and detail
- Koniocellular: detection of blue-yellow colour
How much of the cortex is dedicated to vision?
Over 50%
What are 3 features of the primary visual cortex?
- Straited
- Composed of retinotopic map
- Sensitive to particular orientations of light
What is the dorsal stream involved in?
Planning and movement
What is the ventral stream involved in?
Identifying objects and colour information
