Showing papers by "Harvey J. Grill published in 1983"

Quality of acquired responses to tastes by Rattus norvegicus depends on type of associated discomfort

Abstract: Rats were trained to avoid a sugar solution through pairing with LiCl toxicosis (upper gastrointestinal tract discomfort), shock (peripheral pain), or high levels of lactose (lower gastrointestinal tract discomfort) Among animals matched for strength of avoidance of the sugar solution, only the LiCl group showed orofacial responses (eg, gaping) indicative of distaste; the other groups continued to show positive orofacial responses to the sugar solution These results, in conjunction with recent results on humans, are interpreted to represent a distinction between food rejection based primarily on unpalatability (distaste) and food rejection based primarily on anticipated negative consequences of ingestion (danger) The results also support the hypothesis that upper gastrointestinal distress (most probably nausea) plays a special role in negative palatability shifts (acquired distastes) These results have implications for the understanding of predispositions in learning and suggest important differences in the quality (readout) of different types of associations Prior research, by relying on intake measures alone, was insensitive to the differences revealed here by monitoring a wider range of responses

Alternating ingestive and aversive consummatory responses suggest a two-dimensional analysis of palatability in rats.

Abstract: The hedonic response to a taste is typically regarded to be the product of a central integration of gustatory afferent information, which ends in a single decision about the nature and intensity of the response to be given. This hedonic response is often characterized as a point lying along a single dimension of palatability, stretching from strongly positive to strongly negative. The present analysis of species-specific consummatory responses suggests that the final response is not made on the basis of a single central analysis of taste information but rather is the result of a competition between two separate systems that are activated by tastes. A single oral infusion of a taste solution may elicit rapid alternation between ingestive and aversive consummatory responses. Such alternation is better interpreted as due to a simultaneous activation of two palatability dimensions than as a reflection of neutral palatability. When increases in the magnitude of aversive responses are produced by taste mixtures, there is not necessarily a reciprocal decrease in ingestive responses. This asymmetry supports the hypothesis of independent palatability dimensions.

Insulin elicits ingestion in decerebrate rats

Abstract: Insulin administered to rats reliably elicits ingestion of food. To determine whether the neural mechanisms sufficient to control insulin-elicited ingestion are located in or caudal to the forebrain, decerebrate rats were treated with insulin and ingestive responses were measured. Insulin treatment produced hypoglycemia that was comparable, in magnitude and duration, in control and decerebrate rats. Decerebrate and control rats ingested significantly more sucrose solution while hypoglycemic than while normoglycemic. In contrast, insulin did not augment the water consumption of either group. These data indicate that neural systems caudal to the forebrain are sufficient to control ingestive consummatory behavior through the integration of metabolic signals generated by insulin treatment and taste afferent input from the oropharynx.

Neural Controls of Energy Homeostasis Caudal to the Forebrain

Abstract: The forebrain, particularly the hypothalamus, has loomed large in our thinking about the neural control of motivational states, particularly the behavioral and autonomic responses of energy balance in mammals This hypothalamic focus derives from a variety of experimental strategies including ablation, focal lesioning, brain stimulation, and single unit recording Bard (1939, 1940) demonstrated that the hypothalamus is required for the hormonal control of sexual behavior Genital stimulation elicited a stereotyped pattern of sexual consummatory behavior in the absence of hormones in spinal and decerebrated cats At the hypothalamic level, however, these sexual consummatory acts became hormonally controlled — as they are in intact cats Subsequently, hypothalamic control over most hormonal functions has been directly demonstrated Neurons which manufacture polypetide hormones and releasing factors as well as neurons sensitive to humoral substances manufactored outside the brain have been localized within the hypothalamus (Pfaff et al, 1973; Hayward, 1977) A different methodology — electrical stimulation and lesions of diencephalic sites — had also focused attention on the hypothalamus The studies of Hess (1958) demonstrated that a wide range of autonomic responses capable of altering energy homeostasis could be elicited by focal hypothalamic stimulation Subsequent studies have continued to infer a role for the hypothalamus in autonomic response elicitation The specific anatomical and physiological substrate of this control, however, has only begun to be elucidated (Norgren, 1976; Beckstead et al, 1980; Ciriello and Calaresu, 1980)