Neural coding of salt taste quality in the blowflyCalliphora vicina

Abstract

1. This paper and the previous one (Maes and Harms 1986) are concerned with the neural coding of salt taste quality in the blowflyCalliphora vicina. This paper addresses the possibility of ensemble coding, i.e., that information about salt taste quality is contained in the pattern of activity across different receptor types. 2. Data obtained are responses of salt and anion receptor cells in 92 type A labellar taste hairs, and salt and water cells in 129 type B hairs to two mid-range concentrations of LiCl, NaCl, KCl, RbCl and CsCl. 3. The anion and water cells responded differentially to iso-salty stimulus concentrations (eliciting the same salt receptor response). The anion receptors separated 7 out of the 10 pairs of salts, and the water cells 8 out of 10 (Fig. 3). KCl-CsCl was the only pair not clearly separated by any receptor type. 4. A quantitative model for ensemble coding is developed, using a signal-detection approach. Based on the numbers of receptors stimulated in the behavioral experiments of Maes and Bijpost (1979), the model predicts that all pairs of salts, including the pair KCl-CsCl, may be distinguishable behaviorally (Fig. 4). 5. The possible roles of spatial and temporal summation are discussed. 6. The cellular basis for the differences in cation selectivity of the receptor cell types is discussed.