Neurophysiology of Olfaction and Gustation

Question 1

What is anosmia?

Answer 1

Loss of sense of smell

Question 2

What is aguesia?

Answer 2

Loss of sense of taste

Question 3

What are tastants?

Answer 3

Chemical compounds that bind taste receptors and impart the primary flavor categories (sweet, salty, bitter, sour, unami)

Question 4

What are odorants?

Answer 4

Chemical compounds that bind odorant receptors that impart an odor

Question 5

What do sweet food signal?

Answer 5

Presence of carbohydrates that serve as an energy source

Question 6

What do salty tastes govern?

Answer 6

Intake of Na and other salts, essential for maintaining the body’s water balance and blood circulation

Question 7

What do umami tastes reflect?

Answer 7

Food’s protein content due to the presence of glutamate and a few other amino acids

Question 8

What do sour tastes signal?

Answer 8

Presence of dietary acids; because sour tastes are generally aversive, we avoid ingesting excess acids and overloading the mechanisms that maintain acid-base balance for the body

Question 9

What do bitter tastes signal?

Answer 9

Innately aversive and is thought to guard against consuming poisons, many of which taste bitter to humans

Question 10

What is the function of the nucleus of the solitary tract?

Answer 10

Receives multiple sensory inputs from vagus nerve that relays information about the viscera; early site of gustatory and visceral information; reflex circuits forms basis for salivary secretions, mimetic responses and swallowing

Question 11

What is the function of the ventral posterior medial nucleus of the thalamus?

Answer 11

Relay station for taste perception; discriminative aspects of taste are processed here

Question 12

What is the function of the gustatory cortex?

Answer 12

Made of the insular taste cortex, operculum of frontal lobe, and post-central gyrus; physiologically we refer to these areas collectively as the gustatory cortex

Question 13

What is the function of the hypothalamus and amygdala?

Answer 13

Affective aspects of eating, emotional context to eating, memories of eating (amygdala); integration of homeostatic mechanisms of eating like hunger (hypothalamus); interplay between eating and calming effects of food take place in the limbic and reward system

Question 14

What is the function of the orbitofrontal cortex?

Answer 14

Integrating visual, somatosensory, olfaction, and gustatory stimuli to collectively appreciate the flavor of food

Note: taste and flavor are not interchangeable terms

Question 15

What is the function of the anterior olfactory nucleus?

Answer 15

Relay station to ipsilateral and contralateral cortices and is poorly understood

Question 16

What is the function of the piriform cortex and lateral hypothalamus?

Answer 16

Control of appetite and how olfactory input influences appetite and hunger

Question 17

What is the function of the piriform cortex and medial orbitofrontal cortex?

Answer 17

Integration of sight, smell, and taste of food; appreciation of the flavor of food

Question 18

What is the function of the anterior cortical amygdaloid nuclei?

Answer 18

Emotional learning, olfactory fear conditioning

Question 19

What is the function of the periamygdaloid cortex?

Answer 19

Integration of the emotional aspect of food as elicited by odor

Question 20

What is the function of the entorhinal cortex and hippocampus?

Answer 20

Memory formation and how olfactory input facilitates both memory and recall; connections within the limbic system and entorhinal cortex are responsible for the highly evocative experience of memory upon odor sensation