the brain via the lower brainstem (Fig. 13.2) and connect with cells in
the nucleus solitarius, from which two axon tracts emerge: one head-
ing into the thalamus, and thence to the insula and to the somatosen-
sory cortex in the parietal lobe (see Chapter 16), and the other
heading to the hypothalamus and the amygdala. Neural activity in
these several regions of the brain is somehow related to the subjective,
perceptual qualities of different tastes, as well as associated emotional
associations—the yums! and yuks!
In addition to the five tastes, other perceptual qualities are associated
with foods that also begin with the detection of molecules in the
mouth. These qualities are not at the present time considered tastes,
even though they are akin to tastes. Perhaps most significant among
these is the quality of hotness or spiciness or pungency—as from chili,
black pepper, mustard, horseradish, wasabi, ginger, and garlic. The
pungent or hot qualities of these plants are associated with molecular
components that activate various receptors in the mouth. However,
signals from these receptors enter the brain via pathways different
from those associated with the primary tastes. They enter via the fifth
cranial nerve (trigeminal nerve) and are received by regions of the
brain closely associated with the perception of pain. This is the reason
that taste scientists do not call spicy hotness a taste, even though
most people would consider it to be taste quality.