Trigeminal deafferentation and hunger in the pigeon (Columbia livia).

The location and distribution of the pigeon's trigeminal nerve permit deafferentation of the oral region without affecting motor functions. Although trigeminal deafferentation does not affect drinking, it reduces the efficiency of the consummatory response of eating and disrupts motivational processes underlying hunger and weight regulation. Although the two types of deficit may be experimentally dissociated, trigeminal deafferentation invariably affects both sensorimotor and motivational mechanisms. The deficits in food intake and weight regulation seen after trigeminal deafferentation in the pigeon resemble some components of the "lateral hypothalamic syndrome" in the rat. The results are related to recent studies of the contribution of peripheral and central oropharyngeal factors to the neural control of food intake in both rat and pigeon.