Department of Psychology and Program in Neuroscience, University of Delaware, Newark, Delaware 19716, USA
Studies investigating fine details of gustatory coding in the
domain of each basic taste quality have been completed for sweet,
salt, and sour stimuli. In the present experiment, we used chemicals
that humans describe as predominantly bitter. We recorded the
activity of 50 taste neurons in insular cortex of two cynomolgus
macaques. Stimuli were water, fruit juice, glucose, NaCl, HCl,
and 16 bitter solutions. In a multidimensional taste space the
16 bitter stimuli formed a coherent cluster composed of three
main subgroups: (1) QHCl, phenylalanine, theophylline, caffeine,
propyl-thiouracil (PROP), and phenylthiocarbamide (PTC), all
of which humans describe as rather purely bitter, (2) MgCl
2,
CaCl
2, NH
4Cl, and arginine, which humans describe as salty-bitter,
and (3) urea, cysteine, and vitamin B
1, which are described
as sour-bitter. Vitamin B
2, histidine and nicotine were in the
center of the bitter cluster. Human descriptions of taste qualities
conformed well to the presumed quality of each stimulus as inferred
from its position in the multidimensional space (MDS), reinforcing
the use of the macaque as a neural model for human gustation.
