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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.

BACKGROUND:Noninvasive prenatal screening (NIPS) using plasma cell-free DNA has gained tremendous popularity in the clinical assessment of fetal aneuploidy. Most, if not all, of these tests rely on complex and expensive massively parallel sequencing (MPS) techniques, hindering the use of NIPS as a common screening procedure.

To examine how resource competition contributes to patch-use behaviour, we examined domestic chicks foraging in an I-shaped maze equipped with two terminal feeders. In a variable interval schedule, one feeder supplied grains three times more frequently than the other, and the sides were reversed midway through the experiment. The maze was partitioned into two lanes by a transparent wall, so that chicks fictitiously competed without actual interference. Stay time at feeders was compared among three groups. The "single" group contained control chicks; the "pair" group comprised the pairs of chicks tested in the fictitious competition; "mirror" included single chicks accompanied by their respective mirror images. Both "pair" and "mirror" chicks showed facilitated running. In terms of the patch-use ratio, "pair" chicks showed precise matching at approximately 3:1 with significant mutual dependence, whereas "single" and "mirror" chicks showed a comparable under-matching. The facilitated running increased visits to feeders, but failed to predict the patch-use ratio of the subject. At the reversal, quick switching occurred similarly in all groups, but the "pair" chicks revealed a stronger memory-based matching. Perceived competition therefore contributes to precise matching and lasting memory of the better feeder, in a manner dissociated from socially facilitated food search.

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