Neuroanatomical Substrates Involved in the Control of Food Intake

Abstract

Five neural pathways were reviewed regarding their specific role in the control of food intake in birds. The five pathways included the trigeminal sensorimotor system, the visual system/basal ganglia pathway, the gustatory system, the olfactory pathway, and the autonomic nervous system/parasympathetic pathway. The trigeminal system is the pathway best understood among the five systems associated with feeding. It begins with sensory nerves innervating the upper and lower mandibles and buccal cavity and ends with nerves projecting to jaw muscles. The function of the pathway is to control the grasping and mandibulation of pellets or seeds. The visual system includes both the tectofugal and thalamofugal pathways. Both visual pathways interact with the avian paleostriatal complex. The latter is equivalent to the mammalian basal ganglia. The second pathway is important in food recognition as well as in orienting the body with respect to its position in three-dimensional space. The third neural circuit involves the sense of taste. Approximately 300 taste buds have been identified within the buccal cavity of the chicken, suggesting that the gustatory system is better developed than once thought. The fourth pathway involves the olfactory system; as in the visual system, more than one pathway has been identified. The dominant pathway appears to project to the piriform cortex, a structure that may play a role in monitoring essential amino acid contents of the brain. The fifth pathway involves an interaction of the hypothalamus and the dorsal motor nucleus of the vagus. This pathway is important in activating the parasympathetic nervous system and in preparing an organism to feed. All five pathways play different roles in controlling food intake in birds.

Neuropeptide Control of Feeding Behavior in Birds and Its Difference with Mammals

“…The control of the beak and the visual, taste, and smell sensations are also thought to be important in controlling feeding behavior. These sensations are sent to the central nervous system via specific pathways, such as the trigeminal sensorimotor system (for the control of grasping and mandibulation of the diet), the tectofugal and thalamofugal pathways (for visual sensation), the gustatory system, and the olfactory pathway (Kuenzel, 1989). The autonomic nervous system/parasympathetic pathway is also important in regulating feeding behavior in birds (Kuenzel, 1989).…”

Unfolding the codes of short-term feed appetence in farm and companion animals. A comparative oronasal nutrient sensing biology review

“…All solid and liquid nutrients enter the digestive system on a non-continuous flow (i.e., meals) and are directed to the gastrointestinal tract through the oral cavity. Before swallowing occurs, food is scrutinized and discriminated according to several chemical and physical parameters that determine food palatability (Kuenzel 1989;Hyde and Witherly 1993;Forbes 1998). Therefore, chemosensory systems located in the oronasal cavity play a crucial role in nutrient intake.…”

“…The peripheral senses most relevant to feed location and evaluation include vision, audition, smell, taste and somatosensing (Kuenzel 1989;Forbes 1998). The last three are found in the oral and nasal cavities (from now on referred to as oronasal) (Dulac 2000).…”

“…Self-nourishment mechanisms are driven by a chemosensory code (or codes) that sense the nutritional value of available food sources and translate it into a physiological stimulus that will trigger or discourage consumption in a fasted state (Kuenzel 1989;Forbes 1998;Huang et al 2006;Bachmanov and Beauchamp 2007). These physiological stimuli have been referred to as peripheral and postingestive (but pre-absorptive), and have a direct and short-term impact on meal initiation and meal size (Booth 1990;Hyde and Witherly 1993;Rauw et al 2006).…”

Effects of various energy and protein levels during sequential feeding on feed preferences in meat-type chickens

“…The short-term control occurs from meal to meal. It is primarily governed by sensorial cues (visual, tactile and olfactory) (Kuenzel, 1989;Picard et al, 2002) and then by satiety signals generated in response to nutrient content and the physical presence of feed or of specific components in the gut (Denbow, 1994).…”