Perception 2 Flashcards
Vision and Multimodal Perception
What are the steps in the visual pathway?
Stimulus = light
1. Eye (remote sensation)
2. Lens inverts and focuses
3. Retina (photoreceptors)
4. Light causes changes in photopigments
5. Photoreceptors connect with bipolar cells that synapse with retinal ganglion cells (neurons)
6. Retinal ganglion cells fire action potentials
7. Optic nerve
8. Optic chiasm
9. Thalamus (LGN)
10. Optic radiation
11. Primary visual cortex (V1)
12. Secondary visual areas (V2, V3, etc)
What are photoreceptors?
They are light sensitive cells not neurons.
Are photoreceptors involved with action potentials?
Photoreceptors don’t fire action potentials it is a chemical change instead
What are the 2 types of photoreceptors?
Rods and Cones
What are rods useful for?
Rods are useful at night
What are cones useful for?
Cones are useful for daytime vision and color (3 types of cones for color vision)
What is contralateral crossover in the visual pathway?
Left visual field to the right hemisphere
When do optic fibers project ipsilaterally in visual pathway?
Optic fibers from the temporal half of the retina project ipsilaterally (same side - don’t cross at chiasm)
When do optic fibers project contralaterally in the visual pathway?
Optic fibers from the nasal half of the retina cross over at the chiasm (contralateral)
What is the retinogeniculate pathway?
When input from both eyes joins together
What is retinotopy?
Neighboring regions in the brain respond to adjacent regions in visual space
What is cortical magnification?
Center of gaze is over-represented in cortex
How is the visual system organized?
Retinoptically (based on space)
What is the Visual Hierarchy?
As you go through the visual pathway optimal stimuli increase in complexity and receptive field size (from retina - the cortex)
Where is the primary visual cortex located?
V1 is located in the posterior occipital lobe
Where are the secondary visual areas located (V2, V3, etc)?
They surround the primary visual cortex
How do lateral geniculate nucleus (LGN) cells respond?
They are either on-center (off surround) or off-center (on-surround) cells that respond to light accordingly
What is surround inhibition?
When receptive fields in the visual cortex are organized so that light in the center of field will activate a cell, while light in the periphery will inhibit it
Why have surround inhibition?
It sharpens contrast and edge detection
What is the fundamental principle of perception?
The brain cares about change
What does the cortical area, V1 like?
Likes oriented lines at various angles
What does the cortical area, V4 like?
Likes colors and shapes
What is V4 responsible for?
Color vision
What does a lesion to the V4 area cause?
Achromatopsia
