Integrating Hunger with Rival Motivations

• Published in: Trends in endocrinology and metabolism Vol. 31; no. 7; pp. 495 - 507
• Main Authors: Hickey, Ames K. Sutton, Krashes, Michael J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.07.2020
• Subjects: AgRP neurons; Animals; behavior; Endocrinology and Metabolism; energy status; Feeding Behavior - physiology; food consumption; Humans; Hunger - physiology; Motivation - physiology; motivational drive; neural circuits; Neurons - metabolism; food consumption; energy status; behavior; AgRP neurons; motivational drive; neural circuits; e nergy status
• ISSN: 1043-2760; 1879-3061; 1879-3061
• DOI: 10.1016/j.tem.2020.04.006

Motivated behaviors have fascinated neuroscientists and ethologists for decades due to their necessity for organism survival. Motivations guide behavioral choice through an intricate synthesis of internal state detection, external stimulus exposure, and learned associations. One critical motivation, hunger, provides an accessible example for understanding purposeful behavior. Neuroscientists commonly focus research efforts on neural circuits underlying individual motivations, sacrificing ethological relevance for tight experimental control. This restrictive focus deprives the field of a more nuanced understanding of the unified nervous system in weighing multiple motivations simultaneously and choosing, moment-to-moment, optimal behaviors for survival. Here, we explore the reciprocal interplay between hunger, encoded via hypothalamic neurons marked by the expression of Agouti-related peptide, and alternative need-based motivational systems. Individual motivational systems, such as hunger, enact behavioral output based on real-time computations of internal state, external cues, and learned representations.Motivational drives serve specific needs and often compete with one another for expression.An organisms’ energy status endows the capacity to shape contending survival-based behavioral repertoires including threat detection/avoidance, thirst/drinking, sleep/rest, thermoregulation, pain/sickness, and intraspecific social interactions such as mating and territorial aggression.While hunger can be largely artificially mimicked by stimulation of AgRP neurons in the hypothalamus, the behavioral manifestation of AgRP-evoked stimulation is largely dependent on experimental context.While it is assumed that an individual’s energy state reflects impending food intake, these readouts can be misinterpreted if subjects are studied in an experimental vacuum.To better understand the reciprocal influence and interplay between hunger and rival motivational systems, a more ecological experimental design should be implemented to bridge together ethology and neuroscience.