Birds have primate-like numbers of neurons in the forebrain

Abstract

Some birds achieve primate-like levels of cognition, even though their brains tend to be much smaller in absolute size. This poses a fundamental problem in comparative and computational neuroscience, because small brains are expected to have a lower information-processing capacity. Using the isotropic fractionator to determine numbers of neurons in specific brain regions, here we show that the brains of parrots and songbirds contain on average twice as many neurons as primate brains of the same mass, indicating that avian brains have higher neuron packing densities than mammalian brains. Additionally, corvids and parrots have much higher proportions of brain neurons located in the pallial telencephalon compared with primates or other mammals and birds. Thus, large-brained parrots and corvids have forebrain neuron counts equal to or greater than primates with much larger brains. We suggest that the large numbers of neurons concentrated in high densities in the telencephalon substantially contribute to the neural basis of avian intelligence.intelligence | evolution | brain size | number of neurons | birds

You Do Not Mess with the Glia

“…Importantly, this cell quantification technique has been found by three independent groups to yield results that are comparable to those obtained with unbiased stereology, but are much faster to obtain and far less prone to user error and undersampling [66][67][68]. The consistency of the approach and technique across studies allowed us to collect data that could be compared systematically across structures in individual brains; across individuals of the same species; across species within a clade; across mammalian clades ( Figure 4); and even across mammals, birds, and non-avian reptiles [53][54][55][56][57][58][59][60][61][62][63][64][69][70][71]. While published results have so far been limited to numbers of neuronal and non-neuronal cells, one advantage of the isotropic fractionator is that, because all tissue heterogeneities in cell distribution are literally dissolved, only very small samples are required for counting, which allows for storage of the remaining suspension at −20 • C for later studies employing new markers or morphological criteria [65].…”

Animal Consciousness

“…A recent study in parrots and songbirds emphasized the importance of numbers of telencephalic neurons in the pallium which provide a means of increasing computational capacity. It supports the concept these birds have advanced behavioural and cognitive complexity (Olkowicz et al, 2016). However, this claim about the emergence of consciousness from a specific brain organization ignores an important fact about the evolution of different nervous systems: these structures, absent in species evolutionarily distant from mammals or birds, such as invertebrates, could eventually be functionally substituted by other structures.…”

Framework for integrating animal welfare into life cycle sustainability assessment

“…It is restricted to space allowance and freedom of movement, whereas many more conditions determine an animal's welfare. The (Azevedo et al 2009, Herculano-Houzel 2009 b (Herculano-Houzel 2016) c The number only refers to neocortical neurons (Jelsing et al 2006); hence, it underestimates the cortical neurons d (Olkowicz et al 2016) e The body mass of a salmon was assumed to equal 4.5 kg (FRS Marine Laboratory 2006), while the brain:body mass ratio was assumed to equal that of a shark-1:2496 (Serendip 2016) f (Lobster Institute 2016) g (Burne et al 2011;Shulman and Bostrom 2012) h The factor difference between an adult insect and the larva (a mealworm is the larva of the mealworm beetle) was assumed to equal that of a zebrafish, which is a factor of 10: a larval zebrafish has 100,000 neurons (Naumann et al 2010), while an adult zebrafish has 1 million neurons (Alivisatos et al 2012) (Bartussek 1995a(Bartussek , 1995b(Bartussek , 1996 and the Welfare Quality® Consortium (Welfare Quality® 2009aQuality® , 2009bQuality® , 2009c can, however, not be applied at large scale due to data scarcity. Therefore, a balance must be found between scalability and indicator complexity.…”