The organization of taste sensibilities in hamster chorda tympani nerve fibers.

Abstract

Electrophysiological measurements of nerve impulse frequencies were used to explore the organization of taste sensibilities in single fibers of the hamster chorda tympani nerve. Moderately intense taste solutions that are either very similar or easily discriminated were applied to the anterior lingual surface. 40 response profiles or 13 stimulus activation patterns were considered variables and examined with multivariate statistical techniques. Three kinds of response profiles were seen in fibers that varied in their overall sensitivity to taste solutions. One profile (S) showed selectivity for sweeteners, a second (N) showed selectivity for sodium salts, and a third (H) showed sensitivity to salts, acids, and other compounds. Hierarchical cluster analysis indicated that profiles fell into discrete classes. Responses to many pairs of effective stimuli were covariant across profiles within a class, but some acidic stimuli had more idiosyncratic effects. Factor analysis of profiles identified two common factors, accounting for 77% of the variance. A unipolar factor was identified with the N profile, and a bipolar factor was identified with the S profile and its opposite, the H profile. Three stimulus activation patterns were elicited by taste solutions that varied in intensity of effect. Hierarchical cluster analysis indicated that the patterns fell into discrete classes. Factor analysis of patterns identified three common unipolar factors accounting for 82% of the variance. Eight stimuli (MgSO4, NH4CI, KCI, citric acid, acetic acid, urea, quinine HCI, HCI) selectively activated fibers with H profiles, three stimuli (fructose, Na saccharin, sucrose) selectively activated fibers with S profiles, and two stimuli (NaNOs, NaCI) activated fibers with N profiles more strongly than fibers with H profiles. Stimuli that evoke different patterns taste distinct to hamsters. Stimuli that evoke the same pattern taste more similar. It was concluded that the hundreds of peripheral taste neurons that innervate the anterior tongue play one of three functional roles, providing information about one of three features that are shared by different chemical solutions.

Discrete Innervation of Murine Taste Buds by Peripheral Taste Neurons

“…Although the present data on the bud-ganglion cell wiring does not bear directly on taste quality coding, it is consistent with such a hypothesis and with the specificity of responses recorded from some ganglion cells and their peripheral fibers. On the other hand, the present results cannot rule out the possibility that branches of single fibers may synapse with several different types of receptor cells within a single bud, accounting for broad sensitivity (Boudreau, 1971;Frank, 1973;Pfaffmann et al, 1979;Frank et al, 1988;Lundy and Contreras, 1999;Breza et al, 2005;Sollars and Hill, 2005).…”

“…This explains the response specificity of some individual taste nerve fibers (Boudreau et al, 1971;Frank, 1973;Pfaffman et al, 1979;Frank et al, 1988;Sollars and Hill, 2005), particularly because sweet, amino acid, and bitter receptors are expressed in distinct populations of taste cells (Chandrashekar et al, 2000;Nelson et al, 2001Nelson et al, , 2002. Although anatomical evidence for such an exclusive relationship is lacking at the level of single receptor and ganglion cells, the relationship between single buds and their innervating ganglion cells is tractable neuroanatomically.…”

Responses of single facial taste fibers in the channel catfish, Ictalurus punctatus, to amino acids

“…The popularity of this scheme waned and was replaced recently by classifying a neuron on the basis of the similarity of the total response profile by cluster analysis rather than by basing the classification scheme solely on a fiber's maximal sensitivity to a single stimulus. In some cases, neuron classification by either "best" stimulus or cluster analysis was similar (Frank et al 1988;Pritchard et al 1989;Smith et al 1983); however, for other studies, cluster analysis appeared to be a more accurate method for identifying possible neuron types (Hanamori et al 1988;Michel and Caprio 199 1;Scott and Chang 1984). The obvious parameter that determines whether cluster analysis is preferable to "best" stimulus classification is the tuning profile of the respective fibers.…”

study of taste perception

“…In studies of the generalization of conditioned taste aversions (CTA) in hamsters (M. E. Frank & Nowlis, 1989), experimental stimuli included several representatives of each of the human taste qualities that activated the hamster chorda tympani nerve (M. E. Frank, Bieber, & Smith, 1988). Behavioral generalizations across these stimuli were subjected to cluster analysis, which resulted in tight clusters of representatives of a quality (e.g., citric, acetic, and hydrochloric acids; M. E. Frank & Nowlis, 1989).…”