Characterizing ingestive behavior through licking microstructure: Underlying neurobiology and its use in the study of obesity in animal models

Abstract

Ingestive behavior is controlled by multiple distinct peripheral and central physiological mechanisms that ultimately determine whether a particular food should be accepted or avoided. As rodents consume a fluid they display stereotyped rhythmic tongue movements, and by analyzing the temporal distribution of pauses of licking, it is possible through analyses of licking microstructure to uncover dissociable evaluative and motivational variables that contribute to ingestive behavior. The mean number of licks occurring within each burst of licking (burst and cluster size) reflects the palatability of the consumed solution, whereas the frequency of initiating novel bouts of licking behavior (burst and cluster number) is dependent upon the degree of gastrointestinal inhibition that accrues through continued fluid ingestion. This review describes the analysis of these measures within a context of the behavioral variables that come to influence the acceptance or avoidance of a fluid, and the neurobiological mechanisms that underlie alterations in the temporal distribution of pauses of licks. The application of these studies to models of obesity in animals is also described.

Copyright © 2017 ISDN. Published by Elsevier Ltd. All rights reserved.

Figures

Fig. 1

Example of pause criteria used in licking microstructure and interpretation of measures of licking microstructure (a) Hypothetical example of temporal pattern of licking as a rodent ingests a solution. The black lines represent individual licks, with the majority of interlick intervals occurring ≤250 ms. (i) Pauses of ≥251 and ≤500 ms are referred to as interburst intervals, and the number of licks occurring prior to this pause criterion reflect burst size (Blue lines; Davis & Smith, 1992). (ii) Pauses of > 500 ms represent intercluster intervals, and cluster size is derived from the number of licks occurring prior to this pause criterion (Green lines; Davis & Smith, 1992). (iii) Other studies have used a > 1000 ms pause criterion, and the number of licks occurring prior to this pause criterion reflect burst size (Red lines; Spector et al., 1998). (b) Measures of licking microstructure and their interpretations.