No relative expansion of the number of prefrontal neurons in primate and human evolution.
Level 5 - mechanism / opinion, no new human data
Comparative neuroanatomical tissue analysis (by design analogy, Level 5 bench research)
PubMed 27503881 · doi:10.1073/pnas.1610178113
What was done
The authors analyzed the cellular composition and scaling of the prefrontal cortex in humans and nonhuman primate species. They evaluated the proportion of cortical neurons in the prefrontal region, the distribution of neurons and white matter cells along the anteroposterior axis, and the scaling of gray and white matter volumes relative to cell counts.
What was found
The prefrontal region of both humans and nonhuman primates contains approximately 8% of cortical neurons, with no clear species differences in the anteroposterior distribution of neurons or white matter cells. Human prefrontal gray and white matter volumes matched allometric expectations based on neuron and other cell counts in other primates.
Why it matters
This study challenges the long-held hypothesis that human brain evolution involved a preferential relative expansion of the prefrontal cortex. It suggests human prefrontal expansion followed standard primate scaling rules, with absolute neuron count rather than relative volume distinguishing humans.
Limits
The abstract does not report sample sizes, specific primate species examined, specimen demographics, or exact confidence intervals. It does not assess microstructural features such as synaptic density, dendritic arborization, or neuronal subtype variations.
Cited by
- contradicts The human prefrontal cortex is larger in relation to total brain mass than that of any other species.