Neural correlates of the four primary taste qualities have been researched so far without decisive conclusions. The present study was carried out to find out neural correlates of gustatory qualities, based partly on the idea of across-neurone response patterning presented by Erickson1~ but wholly on the observation on taste quality coding time made by Halpern and Tapper,2~ and regarding spatiotemporal patterns of the nerve impulses in the primary gustatory afferents, i.e., the whole of temporal

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... characteristics of early neural responses of gustatory nerve fibres from taste cells, as correlates of the taste qualities.3) Methods. Twelve rats, both male and female, weighing 280-400 g, of the Wistar strains were used. Anesthesia was produced with sodium pentobarbital (60 mg/kg, i.p.), the animal was fixed in the supine position, and then the trachea was cannulated. Two or three bundles, each of them consisted of one or at most three nerve fibres, was dissected alive out of the chorda tympani. Impulse discharges resulting from gustatory stimulation of the tongue and propagated along each nerve bundle were recorded simultaneously with conventional electrophysiological equipments on a tape recorder (TEAL 3340), and afterwards photographed. Impulse numbers in every successive 50 ms after the response onset were counted for 500 ms period after stimulation. Taste solutions employed as representatives of four primary taste qualities and their concentrations prepared were as follows : : 0.03, 0.1, 0.3 M NaCI ; 0.03, 0.1, 0.3 M LiCI bitter : 0.003, 0.01, 0.03 M Quinine hydrochloride (QHC1) ; 0.0003, 0.001 M Quinine sulphate (Q2H2SO4) ; 0 .03, 0.1, 0.3 M MgSO4 sour: 0.003, 0.01, 0.03 M HC1; 0.003, 0.01, 0.03 M Acetic acid sweet : 0.3, 1.0 M Sucrose; 0.3, 1.0 M Fructose ; 0.1, 0.3 M a-Dimethylurea (a-DU) The tongue was stimulated by flowing test solutions at the rate