1. A patient with multiple sclerosis suddenly developed impaired taste sensation. An MRI revealed a lesion in the left pontine tegmentum. Which of the following statements best describes the distribution of taste loss on the tongue produced by the lesion?

A. Left and right sides of tongue; anterior two thirds of each side
B. Left and right sides of tongue; posterior one third of each side
C. Left side of tongue, both anterior and posterior parts
D. Right side of tongue, both anterior and posterior part

Comment: The ascending gustatory pathway is ipsilateral

2. Which of the following cranial nerves does not provide any gustatory innervation of the tongue and oral cavity?

A. XII
B. X
C. IX
D. VII

Comment: The XIIth nerve innervates tongue muscles

3. The rostral solitary nucleus is to the caudal solitary nucleus, as

A. taste is to smell
B. taste is to touch
C. taste is to pain
D. taste is to visceral sensations

4. A patient with multiple sclerosis has focal demyelination in the pontine tegmentum that damages the ascending gustatory pathway. Which of the thalamic nuclei listed below would be most directly influenced by a reduction in transmission in the taste pathway produced by this demyelination?

A. Ventral posterior lateral nucleus
B. Ventral posterior medial nucleus
C. Medial dorsal nucleus
D. Ventral medial posterior nucleus

Comment: The thalamic gustatory nucleus is the parvocellular division of the ventral posterior medial nucleus. Whereas the medial dorsal nucleus transmits taste information to the orbitofrontal cortex for integrating tastes and smells, it does not receive direct input from the ascending taste pathway.

5. A patient has a seizure disorder and has gustatory hallucinations. Which of the following brain regions is most likely to be directly involved in these hallucinations?

A. Parietal lobe
B. Occipital lobe
C. Frontal lobe
D. Insular cortex

6. A 17-year-old man received a concussion playing football, as a result of a blow to his head. He noticed greatly diminished sense of smell after the incident. Progressively, over the next year, his sense of smell improved. Which of the following is a plausible explanation for the loss and subsequent partial recovery of olfaction?

A. The axons in the olfactory tracts became damaged as they traveled through the cribriform plate when the concussion displaced the brain transiently. Over the next year, these axons regenerated, thereby restoring function.
B. The axons of the primary olfactory neurons became damaged as they traveled through the cribriform plate when the concussion displaced the brain transiently. During the next year, these axons regenerated, thereby restoring function.
C. The concussion disrupted neurogenesis, and it takes many months for neurogenesis to return to normal.
D. The concussion produced inflammation of the olfactory mucosa, thereby damaging primary olfactory neurons, which takes time to repair.

Comment: The axons of primary olfactory neurons are able to regenerate; they are thought to be the only example of maintained capacity for axon regeneration in the adult mammalian brain. These axons are vulnerable to being transected (termed axotomy) by shearing forces during head trauma.

7. Which of the following is not a primary olfactory area?

A. Piriform cortex
B. Entorhinal cortex
C. Insular cortex
D. Amygdala

8. Which of the following provides the best estimate of the number of glomeruli that would express the gene for a particular olfactory receptor?

A. 1
B. 10
C. 100
D. 1000

Comment: Each olfactory receptor gene is expressed in one, or at most only a few, glomeruli.

9. Which of the listed components of the olfactory system is the destination of migrating newborn neurons from the lateral ventricle wall?

A. Olfactory cortical areas
B. Anterior olfactory nucleus
C. Olfactory tracts
D. Olfactory bulb

10. Which of the following statements best describes how olfactory information is projected to the orbitofrontal cortex?

A. Directly from the olfactory bulb
B. Directly from the olfactory tract
C. Directly from the piriform cortex
D. Directly from the ventral posterior medial thalamic nucleus

Comment: The orbitofrontal cortex receives olfactory information from the piriform cortex, either directly or relayed via the medial dorsal nucleus of the thalamus.