Physiology& Behavior, Vol. 49, pp. 855-862. ©Pergamon Press plc, 1991. Printed in the U.S.A.

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Time-Quality Tracking of Monosodium Glutamate, Sodium Saccharin, and a Citric Acid-Saccharin Mixture S H A R O N A. Z W I L L I N G E R A N D B R U C E P. H A L P E R N 1

Section o f Neurobiology and Behavior and Department o f Psychology Cornell University, Ithaca, N Y 14853-7601

ZWILLINGER, S. A. AND B. P. HALPERN. Time-quality tracking of monosodium glutamate, sodium saccharin, and a citric acid-saccharin mixture. PHYSIOL BEHAV 49(5) 855-862, 1991.--The temporal patterns of taste-quality descriptors evoked by 1000-ms duration stimulus liquids flowed through a closed delivery system over the anterodorsal tongue tip region were indicated using touch-typing on a computer keyboard. Single keys corresponded to the taste words of a 23 item code. A computer monitor displayed for subjects the keys pressed and when they were pressed, starting at stimulus delivery. For 2 mM sodium saccharin (NaSac), 75% of the responses were "sweet," 6.5% "sugar"; for NaSac in 10 mM citric acid (Attl.,em), 43% "sour," 20% "citrus," and 11% "sugar"; for 214 mM monosodium glutamate (MSG), 28% "salty," 14% "sour," and 10% 1st "soapy," then "no taste," and finally "bitter." Distilled water received "no taste" on all trials. Response durations were 657 ms for ArtLem, 594 ms for NaSac, 577 ms for MSG. MSG yielded multiple quality responses on 25.5% of the trials; Artl_~m, 9%; and NaSac, 1%. These results are compared with temporal patterns for taste intensity and with unrestricted verbal descriptions of the solutions. Taste MSG

Time Tracking Temporal patterns

Reaction time

Quality

Umami

Saccharin

Citric acid

Taste mixtures

report of portions of this experiment has been made (18).

TASTE perception is an ongoing process that can be studied by obtaining successive response measures over time (6). Both taste intensity and taste-quality descriptions have temporal aspects that are significant, and sometimes crucial, factors in perceived taste [e.g., (1, 5, 13, 16)]. In most gustatory time-course experiments, only taste intensity has been measured. However, time-intensity tracking of a specified taste-quality descriptor was sometimes done [e.g., (2, 3, 14, 15, 17)]. Direct study of temporal changes in taste-quality descriptions over time has been lacking. Goals of the present experiment were: (a) clarifcafion of whether taste-quality descriptors such as soursalty or sweet-citrus (4,10) represent more or less simultaneous and unitary perceptions or successive, multiple taste-quality perceptions, and (b) comparison of the temporal patterns revealed by taste-quality tracking with those previously indicated by taste-intensity tracking. To accomplish these goals, a training and response procedure was developed that permitted a reasonably wide range of taste-quality descriptors, and allowed measurement of the latency and duration of responses. This procedure was combined with a closed taste stimulus delivery system (8) that provided consistent stimulation of a known tongue region. A brief

METHOD

Subjects Four female, nonsmoking, nonpregnant paid volunteers were tested. Their ages ranged from 18 to 20 years old. All were Cornell University students. Subjects were selected by means of a taste screening test (4) from a group of eight volunteers who reported that they could touch-type. Stimuli for the screening test were 25 mM sucrose, 40 mM NaC1, 2 mM HCI and 8 p,M quinine sulfate, each presented 7 times in random order. The criteria for passing the screening test were identifying the tastes of the four solutions consistently; being inconsistent no more than 5 out of 28 times. The same description was not accepted for two or more screening solutions. All five inconsistencies could be for one solution. Subjects were instructed "Your task in this screening session is to describe the taste of the solutions that you will be given." Subjects were not told to use the taste-quality descriptors sweet,

1Requests for reprints should be addressed to Bruce P. Halperu, Department of Psychology, Uris Hall, Cornell University, Ithaca, NY 14853-7601.

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salty, sour and bitter. These tour "basic" tastes were not mentioned in order to avoid biasing the subjects" responses in the main experiment.

Stimuli Three stimulus solutions and distilled water were used in the experiment. The solutions were 2 mM sodium saccharin (NaSac), 214 mM monosodium glutamate (MSG) and a combination of 10 mM citric acid in 2 mM sodium saccharin. This mixture was designated Artificial Lemonade (ArtLem). These stimuli were selected so that time-quality tracking responses could be compared with previous studies (4, 5, 10, 1 l). The citric acid was analytical reagent grade, the NaSac was United States Pharmacopoeia (USP) and the MSG was commercial grade (Ajinomoto). The solutions were prepared in distilled water (conductivity

Time-quality tracking of monosodium glutamate, sodium saccharin, and a citric acid-saccharin mixture.

The temporal patterns of taste-quality descriptors evoked by 1000-ms duration stimulus liquids flowed through a closed delivery system over the antero...
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