Meal initiation controlled by learned cues: basic behavioral properties.

The behavioral properties of meals initiated in response to the presentation of food-associated external stimuli are examined. A Pavlovian conditioning procedure was used to teach animals an association between an arbitrary external cue and food. Subsequent presentations of the conditioned cue reliably led to the initiation of feeding even though rats were tested under conditions of satiety. Several properties of learned external control of feeding were identified. First, the size of meals motivated by exposure to signals for food resembled the level of ingestion characteristic of spontaneous feeding. Second, the potency of externally-controlled intake was influenced by satiety signals arising from previous meals. Third, although presentation of the conditioned cue could be used to influence meal pattern, rats regulated the amount of calories consumed in a 24-h period. These results establish that learning contributes to meal initiation and that mechanisms based on learning do not require (but may interact with) internal energy depletion signals in the control of feeding. The implications of these findings to models of feeding behavior are discussed.