Chapter 6: Visual perception

Question 1

How does general perception takes place?

Answer 1

1. Physical energy is converted by receptors into physiological activity.
2. The physiological activity is projected through various streams to areas of the brain that are concerned with the most basic processing of sensory information (primary sensory areas or projection areas).
3. From the primary sensory areas, information is transmitted to the secondary sensory cortex, which deals with more complex processing of the information.
4. From the secondary sensory areas, information is transmitted to the tertiary areas, where coupling with information from other senses occurs. In these stages the information is processed into higher-order presentations.

Question 2

Are primary sensory areas unimodal or multimodal and why?

Answer 2

Unimodal, because they’re concerned with one specific type of sensory information.

Question 3

Are secondary and tertiary areas unimodal or multimodal and why?

Answer 3

Multimodal, because the convergence of multiple sensory modalities.

Question 4

How does the physiological basis of object perception takes place?

Answer 4

1. The retina of the eyes pickup light information.
2. An initial separation of different visual information takes place.
3. Signals from rods and cones are transmitted to ganglion cells.
4. The axons of ganglion cells form the optic nerve.
5. The optic nerve transmits visual information via the optic chiasm to the cerebrum.
6. The optic nerve projects to the nucleus geniculatis lateralis (NGL) of the thalamus.
7. In the NGL the information is processed in several layers and the visual information is projected to the primary visual cortex via optical radiation.

Question 5

Which 2 types of light-sensitive cells contains the retina and what are their characteristics?

Answer 5

1. Cones = require large amounts of light and are important for colour vision. There are 2 different kinds of cones, sensitive to different parts of the visual spectrum:
   - Blue cones: short wavelengths.
   - Green cones: medium wavelengths.
   - Red cones: long wavelengths.
2. Rods = more sensitive to light and thus require less light, but are insensitive to colour information.

Question 6

What types of ganglion cells are there and what is their function?

Answer 6

• Parvocellular cells (P-cells) = have a small receptive field (high spatial resolution) and transmit mainly information about colour.

*Magnocellular cells (M-cells) = have a large receptive field and transmit mainly information about movement.

• Signals from these 2 types of ganglion cells run in separate streams to the cortex.

Question 7

What does the optic chiasm do?

Answer 7

In the optic chiasm, the nerve paths cross, so that information from the left part of the retina of both eyes enters the left hemisphere and the right part of the retina of both eyes enters the right hemisphere.

Question 8

What are synonyms of the primary visual cortex?

Answer 8

Striate cortex and V1

Question 9

How is visual information stream mainly processed and what does that mean?

Answer 9

• The visual information stream is mainly processed sequentially.
• This means that in successive stages of processing visual input is always converted to higher-order presentation.
• This bottom-up process begins with the basal input that the NGL receives from the retina and in turn transmits to the primary visual cortex. A more specialized processing of the information then takes place in each subsequent step of cortical processing.

Question 10

In which 2 systems is the functional separation from different types of visual information that already took place at the retinal level is continued in the cortex? And what are their functions?

Answer 10

• The occipito-temporal what-route:
• The ventral what-route receives information from the P-cells of the NGL and is involved in the processing of shape, colour and texture, which together are important for the recognition of objects and persons.
• The pathway runs from V1 and V2 through V4 to specific areas in the inferior temporal cortex, the gyrus angularis and structures such as the hippocampus and amygdala.
• The occipito-parietal where-route:
• The dorsal where-route receives information from the M-system and is involved in visuospatial processing, the localization of objects in space, and the control of visually controlled movements to these objects.
• The dorsal route runs from V1 and V2 via V3 to V5.
• From V5, information is projected to areas in the parietal cortex and the upper half of the temporal cortex.