5.6 Vision

Question 1

retina

Answer 1

To perceive objects, we need sensory detectors that respond to the reflected light. As light passes through the lens of the eye, the image is inverted and focused to project on the retina

Question 2

photoreceptors

Answer 2

The deepest layers are composed of millions of photoreceptors that are protein molecules that are sensitive to light

Question 3

Rods (photoreceptors)

Answer 3

contain the photopigment rhodopsin, therefor they are more useful at night, when light energy is low

Question 4

(types of) Cones (photoreceptors)

Answer 4

contain photopsin, they require more intense levels of light, cones are therefor more active during daytime vision. There are three types of cones:
1. Cones that respond to shorter wavelengths, the ‘blue’ part of the spectrum
2. Cones that respond to medium wavelengths, the ‘green’ region
3. Cones that respond to the longer wavelengths, the ‘red’ part

Question 5

fovea

Answer 5

Near the centre of the retina. The cones are densely packed near the fovea. Rods are distributed across the retina.

Question 6

optic nerve

Answer 6

The rods and cones are connected to bipolar neurons that synapse with ganglion cells, the output layer of the retina. The axons of these cells form a bundle, the optic nerve, that transmits information to the central nervous system.

Question 7

lateral geniculate nucleus/ LGN

Answer 7

From the thalamus. Made up of six layers. One type of ganglion cell, the M cell, sends output to the bottom two layers. Another type of ganglion cell, the P cell, projects to the top four layers.

Question 8

receptive field

Answer 8

The area of external space within which a stimulus must be presented in order to activate a cell

Question 9

retinotopic maps

Answer 9

Visual cells from an orderly mapping between spatial location and the neural representation of that dimension. These tonotopic representations are called the retinotopic maps in vision.

Question 10

Hierarchical processing hypothesis

Answer 10

Each area, representing the stimulus in a unique way, successively elaborates on the representation derives by processing in earlier areas. Successive elaboration culminates in formatting the representation of the stimulus so that it matches information in memory.

Question 11

analytic process hypothesis

Answer 11

Each visual area provides a map of external space, each map represents different types of information. This hypothesis suggests that neurons within an area not only code where an object is located in visual space, but also provide information about the object’s attributes.