Extratelencephalic pathways and feeding behavior in the pigeon (Columba livia).

Electrolytic lesions were placed in the tractus septomesencephalicus (TSM) and tractus occipitomesencephalicus (TOM), efferent pathways originating in visual and somatosensorimotor areas of the avian telencephalon and distributing widely to brain stem and spinal nuclear regions. Lesion effects upon several aspects of ingestive behavior were examined using high speed cinematography, operant conditioning procedures and monitoring of intake and feeding responses. While there was no evidence for direct effects upon drinking, both TSM adn TOM lesions were followed by periods of reduced food intake. Disruptions of feeding in TSM birds were mild and relatively transient but birds were hypophagic for prolonged periods. While there were no deficits in the efficiency or accuracy of their feeding responses or their performance in an operant situation, TSM birds displayed an inappropriate seed "sorting" behavior suggestive of lesion effects upon visually controlled food preferences. TOM lesions produced a significant reduction in responsiveness to food (aphagia, hypophagia), impairments in the control of grasping and peck accuracy and a disruption in operant key pecking reinforced by food. These "sensorimotor" and "motivational" deficits were similar to those seen after damage to central trigeminal structures in the pigeon and suggest that TOM is also a component of a putative "feeding system" in the pigeon.