Chapter 5: Sensation and perception

Question 1

What is achromatopsia?

Answer 1

A selective disorder of color perception resulting from a lesion or lesions of the central nervous system, typically in the ventral pathway of the visual cortex.

In achromatopsia, the deficit in color perception is disproportionately greater than that associated with form perception. Colors, if perceived at all, tend to be muted.

Question 2

What does acuity mean?

Answer 2

The capacity to accurately discriminate fine detail.

Question 3

What is meant by adaptation in perception?

Answer 3

In perception, adjustments to the sensitivity of a sensory system to the current environment and to important changes in the environment.

Question 4

What is meant by adaptation in physiology?

Answer 4

In physiology, the reduction in firing rate that typically occurs in the sensory system when a stimulus is continuously present.

Question 5

What is akinetopsia?

Answer 5

A selective disorder of motion perception resulting from a lesion or lesions of the central nervous system.

Patients with akinetopsia fail to perceive stimulus movement, created by either a moving object or their own motion, in a smooth manner.

In severe cases, the patient may only infer motion by noting that the position of objects in the environment has changed over time, as if the patient were constructing dynamics through a series of successive static snapshots.

Question 6

What is area MT/V5?

Answer 6

A region in the visual cortex containing cells that are highly responsive to motion. Area MT is part of the dorsal pathway, thought to play a role not only in motion perception but also in representing spatial information.

Question 7

What is area V4?

Answer 7

A region in the visual cortex containing cells that are thought to process color information.

Question 8

What are the chemical senses, and why are these senses called the chemical senses?

Answer 8

The two chemical senses are:
1. Taste
2. Smell

These senses are called chemical senses because they depend on environmental molecules for stimulation.

Question 9

What is the cochlear nerve?

Answer 9

Also called auditory nerve. A branch of the vestibulocochlear nerve (8th cranial nerve) that carries auditory information from synapses with hair cells of the cochlea to the cochlear nucleus in the brainstem.

Question 10

What are cochlear nuclei?

Answer 10

Nuclei in the medulla where the cochlear nerve synapses.

Question 11

What are cones?

Answer 11

Photoreceptors that are concentrated in the fovea, providing high acuity but requiring higher levels of light than rods require to activate.

Cones can replenish their pigments more quickly than rods can, and thus provide better daylight vision.

There are 3 types of cones, each sensitive to light of specific wavelengths, mediating color vision.

Question 12

What does cortical plasticity mean?

Answer 12

The capacity of the brain to recognize itself anatomically and functionally.

Question 13

What are cortical visual areas?

Answer 13

Regions of visual cortex that are identified on the basis of their distinct retinotopic maps. The areas are specialized to represent certain types of stimulus information, and through their integrated activity they provide the neural basis for visually based behavior.

Question 14

What is the fovea?

Answer 14

The central region of the retina that is densely packed with cone cells and provides high-resolution visual information.

Question 15

What is a ganglion cell?

Answer 15

A type of neuron in the retina. Ganglion cells receive input from the photoreceptors (rods and cones) and intermediate cells of the retina and send axons to the thalamus and other subcortical structures.

Question 16

What are glomeruli?

Answer 16

The neurons of the olfactory bulb.

Question 17

What is the inferior colliculus?

Answer 17

A part of the midbrain that is involved in auditory processing.

Question 18

What is meant by inaural time?

Answer 18

The difference in time between when a sound reaches each of the two ears. This information is represented at various stages in the auditory pathway and provides an important cue for sound localization.

Question 19

What is the lateral geniculate nucleus (LGN)?

Answer 19

The thalamic nucleus that is the main target of axons of the optic tract. Output from the LGN is directed primarily to the primary visual cortex.

Question 20

What is meant by multisensory integration?

Answer 20

The integration of information from more than one sensory modality. Watching someone speak requires the integration of auditory and visual information.

Question 21

What are nociceptors?

Answer 21

Also called free nerve endings. The somatosensory receptors that convey pain information.

Question 22

What is an odorant?

Answer 22

A molecule conducted through the air that leads to activation of the olfactory receptors and may be perceived as having a fragrance when processed through the olfactory system.

Question 23

What is the olivary nucleus?

Answer 23

A collection of nuclei in the medulla and pons that is the first site were auditory information from the right and left ear converges.

Question 24

What are photoreceptors?

Answer 24

Specialized cells in the retina that transduce light energy into changes in membrane potential. The photoreceptors are the interface for the visual system between the external world and the nervous system.

The human eye has two types of photoreceptors:
1. Rods
2. Cones

Question 25

What is the primary auditory cortex (A1)?

Answer 25

The initial cortical processing area of the auditory system.

Question 26

What is the primary gustatory cortex?

Answer 26

The initial cortical processing area for gustation (the sense of taste), located in the insula and operculum.

Question 27

What is the primary olfactory cortex?

Answer 27

Also called pyriform cortex. The initial cortical processing area for olfaction, located at the ventral junction of the frontal and temporal cortices, near the limbic cortex.

Question 28

What is the primary somatosensory cortex (S1) and what does it contain?

Answer 28

The initial cortical processing area for Somatosensation, including Brodmann areas 1,2, and 3.

This area of the brain contains a somatotopic representation of the body called the sensory homunculus.

Question 29

What is the primary visual cortex (V1)?

Answer 29

The initial cortical processing area for vision, located in the most posterior portion of the occipital lobe, also known as Brodmann area 17.

Question 30

What is meant by proprioception?

Answer 30

The awareness of the position of one’s own body parts, such as limbs. This awareness arises from the information provided by specialized nerve cells at the linkage of the muscles and tendons.

Question 31

What is meant by receptive field?

Answer 31

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

For example, cells in the visual cortex respond to stimuli that appear within a restricted region of space. In addition to special position, the cells may be selective to other stimulus features, such as color or shape.
Cells in the auditory cortex also have receptive fields. The cell’s firing rate increases when the sound comes from the region of space that defines its receptive field.

Question 32

What is the retina?

Answer 32

A layer of neurons along the back surface of the eye. The retina contains a variety of cells, including photoreceptors (the cells that respond to light) and ganglion cells (the cells whose axons form the optic nerve).

Question 33

What is the retinotopic map?

Answer 33

A topographic representation in the brain in which some sort of orderly spatial relationship is maintained that reflects spatial properties of the environment in an eye-based reference frame.

For example, primary visual cortex contains a retinotopic map of the contralateral side of space, relative to the center of gaze.

Multiple retinotopic maps have been identified in the cortex and subcortex.

Question 34

What are rods?

Answer 34

Photoreceptors that have a lower threshold for light stimuli than cones have, and thus enable vision in low-light conditions. Rods are found in the periphery of the retina and not in the fovea. Many rods connect to one ganglion cell.

Question 35

What are saccades?

Answer 35

The rapid eye movements that are made to change fixation from one point to another. A saccade lasts 20 to 100 ms.

Question 36

What is the secondary somatosensory cortex (S2)?

Answer 36

The area of the brain that receives inputs from primary somatosensory cortex and processes higher-level somatosensory information.

Question 37

What is the superior colliculus?

Answer 37

A subcortical visual structure located in the midbrain. The superior colliculus receives input from the retinal system and is interconnected with the subcortical and cortical systems. It plays a key role in visuomotor processes and may be involved in the inhibitory component of reflexive attentional orienting.

Question 38

What is meant by synesthesia?

Answer 38

A mixing of the senses whereby stimulation of one sense (e.g., touch) automatically causes an illusory perceptual experience in the same or another sense (e.g., vision).

Question 39

What is a tastant?

Answer 39

A food molecule that stimulates a receptor in a taste cell to initiate the sensory transduction of gustation.

Question 40

What is the tonotopic map?

Answer 40

A mapping of different frequencies onto the hair cells along the cochlear canal and also the auditory cortex, with neighboring frequencies represented in neighboring spatial locations.