Selective contribution of the telencephalic arcopallium to the social facilitation of foraging efforts in the domestic chick.

To investigate the neural basis of socio-economic behaviors in birds, we examined the effects of bilateral electrolytic lesions of arcopallium (Arco, the major descending pallial area of the avian telencephalon) and the surrounding nuclei in domestic chicks. We tested foraging effort (running distance) in an I-shaped maze with two food patches that delivered food in a biased manner according to a variable interval schedule. Normally, chicks run back and forth between the patches, and the patch use time matches the respective food delivery rate. In the paired phase, even without actual interference of food, chicks showed social facilitation of running effort compared with the single phase. Chicks with lesions in the Arco and lateral Arco showed significant reductions in social facilitation. The lesion effects of the lateral Arco were particularly selective, as it was not accompanied by changes in running distance in the single phase. Lesions of the nidopallium and nucleus taeniae of the amygdala produced no changes in foraging behavior. On the other hand, the Arco lesion did not impair social facilitation of operant peck latency. In accordance with this, anterograde tracing revealed characteristic projections from the lateral Arco to the extended amygdala, hippocampus, and septum, as well as wide areas of limbic nuclei in the hypothalamus and medial areas of the striatum including the nucleus accumbens. Pathways from the lateral Arco could enable chicks to overcome the extra effort investment of social foraging, suggesting functional and anatomical analogies to the anterior cingulate cortex and basolateral amygdala in mammals.