18.0 Physiology of Vision Flashcards
What are blobs?
Blobs are columns spanning all six layers of V1, and respond to one wavelength of light, thereby allowing us to see color.
Each blob corresponds to one cone cell.
What is the sequence of cells the signal passes through from the time a photoreceptor is hit with a photon to when the signal leaves the eye?
Photoreceptor takes in the signal
Bipolar cells convey the signal (and so do horizontal cells)
Ganglion cells pick up the signal, and their axons converge to form the optic nerve and carry the signal out of the eye.
What is the function of the dorsal pathway of outputs from V1?
The “where” pathway.
Completes motor acts based on movement, and passes through V3, which is in charge of determining motion.
How do off-center bipolar cells depolarize in the absence of light in their center?
They have a non-NMDA receptor that responds directly to the glutamate produced by rods and cones in low light conditions.
What is the function of the hypothalamus in visual processing?
Fibers from the optic tract enter the hypothalamus and regulate day night entrainment of circadian rhythms.
How does an on-center bipolar cell become depolarized when struck with a photon in the center?
Typically light would be inhibitory rather than excitatory becuase it stops rods and cones from producing the EAA glutamate. On-center cells get around this by having a GPRC that opens in the absence of glutamate, which then depolarizes the cell by closing cGMP-gated ion channels.
What are the functions of V2, V3, and V4?
V2: Depth
V3: Motion
V4: Color
Why does the ciliary muscle contract during near vision?
This allows the suspensory ligaments to relax, allowing the lens to become more round.
What are the functions of the lateral geniculate body?
Retinotopic organization
Understanding relative positions of objects in 3d space.
Understanding movement relative to an object.
Coordinates the two eyes to allow us to focus.
What neurotransmitter do bipolar cells use to trigger the ganglion cells they target?
Glutamate
What are ocular dominance columns?
Columns of V1 cortex that only responds to one eye or the other.
Describe the path of light from the cornea to the photoreceptors in the eye.
Light passes through the cornea, through the aqueous humor, then the pupil, then the lens, through the vitreous humor, through the layers of the retina, then activates a photoreceptor at the back. The electrical signal then goes forward.
Layers of the retina: ILM, NL, GCL, IP, IN, OP, ON, OL, R&C, RPL, LV, Ch
What is the function of the ventral pathway of outputs from V1?
The “what” pathway.
Runs through V2 and V4, in charge of depth and color.
Primarily in charge of naming objects and copying them from a reference image.
Facial recognition.
What is the function of the superior colliculus?
Saccadic eye movements (jumping between two points quickly)
Connects to the tectospinal tract (responds to turn the head to loud noises)
Creates a map of visual space to activate motor responses to move the eyes to an intended target. (Prevents overshoot of the eyes)
What is the purpose of the pretectal nucleus?
Pupillary light reflex from the lateral geniculate nucleus to the Edinger Westphal nucleus.
