Large brains: Big unknowns in cellular neuroscience

Abstract

Contemporary cellular neuroscience is strong on small but weak on large brains. Large brains have lower neuronal densities than smaller brains. We outline opposing functional interpretations of this result. Analysis of human brains supports the idea that dendritic complexity matters and might even correlate with intellectual ability. Cortical connectomics revealed an elaboration of disinhibitory motifs in human brains. There is disagreement as to whether glia-to-neuron ratios differ between small and large brains. The elaborate myeloarchitecture of the human brain has long been recognized and novel evidence indicates myelin might play nonconventional structural functions in larger brains. Three-dimensional body-part models in the cortex of tactile specialists point to the significance of the three-dimensional structure of cortical networks. The comparative assessment of brain performance remains one of the biggest challenges in neurobiology. Understanding cellular differences between small and large brains is a neglected, yet fundamental issue for neuroscience and translation.