Q-1. For color vision, which is true?
a) Independent of wavelength of light
b) Dependents on intensity discrimination
c) Involves opponent color cells
d) Minimum at fixation point
Answer: Involves opponent color cells
Explanation:
Two complementary theories of color vision are the trichromatic theory and the opponent process theory. The trichromatic theory, or Young–Helmholtz theory, proposed by Thomas Young and Hermann von Helmholtz states that the retina’s three types of cones are preferentially sensitive to blue, green, and red.
The opponent process theory proposed by Ewald Hering states that the visual system interprets color in an antagonistic way: red vs. green, blue vs. yellow, black vs. white. Activation of one member of the pair inhibits activity in the other.
Q-2. Relative color and luminosity of photoreceptive input under changing light conditions are regulated and maintained by
a) Muller cells
b) Amacrine cells
c) Ganglion cells
d) Retinal astrocytes
Answer: Amacrine cells
Explanation:
Amacrine cells
Most amacrine cells lack typical axons and consequently their dendrites make both incoming and outgoing synapses.
The various classes of amacrine cell serve a number of important functions in vision. AII cells play an essential role in the rod pathway.
Cells appear to be important modulators of photoreceptive signals, and serve to adjust or maintain relative color and luminosity inputs under changing light conditions.
They are probably also responsible for some of the complex forms of image analysis known to occur within the retina, such as directional movement detection.
Q-3. Rods & Cones are differ in all except
a) Light Sensitivity
b) Wavelength
b) Acuity
d) Signal Transduction
Answer: Signal Transduction
Explanation:
The mechanism of signal transduction or photo-transduction is almost similar in both rods and cones,
Rods and cones differ in structure, photochemical molecules, sensitivity, retinal distribution, synaptic connection and function.
Q-4. The fibers from the contra-lateral nasal hemi-retina project to following layers of the lateral geniculate nucleus.
a) Layers 2, 3 & 5
b) Layers 1, 2 & 6
c) Layers 1, 4 & 6
d) Layers 4, 5 & 6
Answer: Layers 1, 4 & 6
Explanation:
Fibres from medial hemi-retina of opposite eye end in lamina 1, 4 and 6 and fibres from lateral hemi-retina of same side end in lamina 2, 3 and 5.
Important point:
Each geniculate body contains six well defined layers. Layer 1 and 2 have large cells and are called magno-cellular, whereas layer 3 to 6 have small cells and are called parvo-cellular.
Q-5. The parvo-cellular pathway form lateral geniculate nucleus to visual cortex is most sensitive for the stimulus of
a) Color contrast
b) Luminance contrast
c) Temporal frequency
d) Saccadic aye moments
Answer: Color contrast
Explanation:
The parvo-cellular pathway from layer 3-6 carries signal for color vision, texture, shape and fine details.
Important point:
Magno-cellular pathway from layer 1 and 2 carries signals for detection of movement, depth and flicker.
Q-6. Most afferent fibres from the lateral geniculate nucleus terminate in the primary visual cortex is
a) Layer 1
b) Layer 2 and 3
c) Layer 4
d) Layer 5 and 6
Answer: Layer 4
Explanation:
Visual cortex has six layers. The axons from the lateral geniculate nucleus that form the magno-cellular pathway end in layer 4C. Many of the axons that form the parvo-cellular pathway also end in layer 4C.
Important point:
However, the axons from the inter-laminar region end in layers 2 and 3.
Q-7. The blobs of the visual cortex are associated with
a) Ocular dominance
b) Orientation
c) Color processing
d) Saccadic eye movements
Answer: Color processing
Explanation:
Layers 2 and 3 of the visual cortex contain clusters of cell about 0.2 mm in diameter that unlike neighboring cells contain a high concentration of the mitochondrial enzyme cytochrome oxidase. These clusters called blobs. They are arranged in a mosaic in the visual cortex.
Important point:
These blobs are concerned with color vision.