You Are Who You Talk with - A Commentary on Dugas-Ford et al. PNAS, 2012

Over the last decade, the intellectual reputation of birds has been greatly rehabilitated, notably by the studies of Nicky Clayton and coworkers on New Caledonian crows [Clayton, 2007] and the work of Irene Pepperberg and coworkers on African grey parrots [Pepperberg, 2002]. This realization stands quite in contrast to the prior and long-standing view that avian behavior, even the seemingly impressive vocal abilities of parrots for example, was merely driven by rote learning and hardwired stereotypical behavioral routines [Reiner et al., 2004]. This older view was reinforced by the other old notion that the avian telencephalon is largely hypertrophied basal ganglia and is nearly devoid of a neural region that could perform the cognitive operations carried out by the mammalian cerebral cortex [Reiner et al., 2004]. However, the work of Karten and Hodos [1970] beginning nearly 50 years ago, on the organization and function of the avian forebrain, had long shown that the avian telencephalon is not an overgrown basal ganglia, and that it possesses a large region that is functionally akin to the mammalian neocortex [Karten and Hodos, 1970; Karten et al., 1973]. Karten [1991] noted in his theoretical writings that this territory within the avian telencephalon, which encompasses the Wulst, dorsal ventricular ridge (DVR) and arcopallium, possesses the neuron types and connectivity characteristic of the mammalian neocortex, and can thus perform as the neural substrate for cognition. The Wulst, DVR and arcopallium, however, are arrayed as nuclei rather than as layers, which is why earlier neuroanatomists had thought that the nuclear avian telencephalon is largely equivalent to the nuclear basal ganglia of mammals.