Large-scale network organization in the avian forebrain: a connectivity matrix and theoretical analysis

Abstract

Many species of birds, including pigeons, possess demonstrable cognitive capacities, and some are capable of cognitive feats matching those of apes. Since mammalian cortex is laminar while the avian telencephalon is nucleated, it is natural to ask whether the brains of these two cognitively capable taxa, despite their apparent anatomical dissimilarities, might exhibit common principles of organization on some level. Complementing recent investigations of macro-scale brain connectivity in mammals, including humans and macaques, we here present the first large-scale “wiring diagram” for the forebrain of a bird. Using graph theory, we show that the pigeon telencephalon is organized along similar lines to that of a mammal. Both are modular, small-world networks with a connective core of hub nodes that includes prefrontal-like and hippocampal structures. These hub nodes are, topologically speaking, the most central regions of the pigeon's brain, as well as being the most richly connected, implying a crucial role in information flow. Overall, our analysis suggests that indeed, despite the absence of cortical layers and close to 300 million years of separate evolution, the connectivity of the avian brain conforms to the same organizational principles as the mammalian brain.

Birds have primate-like numbers of neurons in the forebrain

“…Superficially, the architecture of the avian brain appears very different from that of mammals, but recent work demonstrates that, despite a lack of layered neocortex, large areas of the avian forebrain are homologous to mammalian cortex (14-16), conform to the same organizational principles (15,17,18), and play similar roles in higher cognitive functions (14,19), including executive control (20,21). However, bird brains are small and the computational mechanisms enabling corvids and parrots to achieve ape-like intelligence with much smaller brains remain unclear.…”

An edge-centric perspective on the human connectome: link communities in the brain

“…Hub nodes are highly connected brain regions with a central position in the network [36] and have been noted to be involved in a variety of cognitive tasks and functions [7,37,38]. Together, the hubs of the brain form a densely connected 'core' or 'rich club' [21, [39][40][41] which has been suggested to play a role in the integration of information between functional domains [19,42]. Considering these properties, we hypothesized a pro- rstb.royalsocietypublishing.org Phil.…”

Implicit learning in cotton-top tamarins (Saguinus oedipus) and pigeons (Columba livia)

“…Part of the reason for this lack of surprise is precisely the growing literature that has indicated comparable performance between primates and avians. This literature articulates with the modern recognition that the avian brain enjoys more similarities with the mammalian brain than may have previously been understood (Colombo & Scarf, 2012;Shanahan, Bingman, Shimizu, Wild, & Güntürkün, 2013;Shimizu, 2009). In the past, these parallels may have been unforeseen, given the understanding that mammals have been evolving separately from birds for nearly 300 million years.…”