primary visual pathway Flashcards
(15 cards)
What is the primary function of the retina in the visual pathway?
The retina contains photoreceptors (rods and cones) that convert light into electrical signals, which are passed to bipolar and then retinal ganglion cells.
What do the optic nerves do?
They carry visual signals from the eyes to the brain, formed by axons of retinal ganglion cells.
What happens at the optic chiasm?
Information from the nasal half of each retina crosses to the opposite side of the brain, helping process visual fields contralaterally.
Where does the optic tract lead?
It carries visual information from the optic chiasm to the lateral geniculate nucleus (LGN) in the thalamus.
What is the function of the lateral geniculate nucleus (LGN)?
It organizes and relays visual signals to the primary visual cortex and has center-surround receptive fields for contrast detection.
Where is the primary visual cortex (V1) located?
In the occipital lobe; also known as the striate cortex.
What are receptive fields in vision?
Areas of the retina where light affects a neuron’s firing rate.
What is center-surround organization?
A receptive field layout where light in the center excites and light in the surround inhibits, enhancing edge and contrast detection.
How do rods differ from cones?
Rods are more sensitive to low light and detect no color; cones are color-sensitive but need bright light.
What are the three types of cones, and what do they detect?
S-cones (short wavelengths – blue), M-cones (medium – green), and L-cones (long – red).
What causes negative afterimages?
Adaptation and rebound effects in retinal ganglion cells after prolonged stimulation.
What are simple cells in V1?
Neurons that respond to bars of light at specific orientations, with distinct excitatory and inhibitory regions.
What are complex cells in V1?
Neurons that respond to moving stimuli and orientation but lack clear ON/OFF zones.
What are the two major visual processing streams beyond V1?
Ventral stream (object recognition – ‘what’) and dorsal stream (spatial awareness – ‘where/how’).
What is blindsight?
A condition where individuals with damage to V1 respond to visual stimuli without conscious awareness, suggesting alternate visual pathways.
