3. From retina to cortex Flashcards
There is inherent ____ in the visual signals our eyes recieve
Ambiguity
What is meant by bi-stable perception?
No d____ c____ leads to v____ a____
No depth cues leads to visual ambiguity
What is the purpose of the following parts of the eye?
1. Pupil
2. Iris
3. Cornea and lens
4. Accommodation
- Where light enters eye
- Adjustable aperture, constricts in bright light to make pupil smaller
- Focuses light on retina
- Ciliary muscles change shape of lens to bring objects into focus at different distances
Photoreceptors are c____ with l____ s____ p____ in o____ s____
Cells with light sensitive photopigments in outer segments
What are Rods?
Contain r____, respond in d____ light, none in f____
Contain rhodopsin, respond in dim light, none in fovea
What are Cones?
T____ types with p____ sensitive to different w____ (l____, m____, s____) - d____ vision
Three types with photopigments sensitive to different wavelengths (long, medium, short) - daytime vision
What are the different types of cells in the last stage in retinal processing?
1. L____ p____ g____ cells
2. S____ m____ g____ cells
3. Cells have ‘r____ f____’ - the part of the r____ from which the g____ cell receives i____
- Large parasol ganglion cells
- Small midget ganglion cells
- Cells have ‘receptive fields’ - the part of the retina from which the ganglion cell receives input
What are three properties of retinal ganglion processing?
1. Poor at spotting …
2. Good at picking out …
3. Filters the input for …
- Poor at spotting gradual change
- Good at picking out sharp edges
- Filters the input for useful info
Within the Lateral Geniculate Nucleus (LGN) there are three types of cells. What are they and what do they detect?
1. M____c____ cells - m____ and f____
2. P____ c____ cells - c____ and d____
3. K____c____ cells - b____-y____
- Magnocellular cells - movement and flicker
- Parvocellular cells - colour and detail
- Koniocellular cells - blue-yellow
50% of the cortex is dedicated to what?
Vision
Prevalence of neutron types is shaped by what early on?
Environmental experience
What did Blakemore and Cooper (1970) find when they raised kitten in striped tubes from birth with vertical or horizontal stripes?
5 hours per day in tube
5 months later: no response to orientation not in tube
Recorded from cells in visual cortex: no neurons that respond to orientation absent in tube
Example of neural plasticity, but with a critical period - ‘use it or lose it’
What do the following streams of processing process?
1. Dorsal - w____
2. Motor system - m____
3. Ventral - w____
4. Hippocampus - m____
- Where
- Movements
- What
- Memory
Processing of some features (e.g. ____) begins at the ____ and gets more complex ‘____’ in the visual processing stream
edges
retina
higher
Cells in different parts of the visual stream are s____ to different features and take in information from a particular r____ f____
selective
receptive field