The primate neocortex in comparative perspective using magnetic resonance imaging.
Level 5 - mechanism / opinion, no new human data
Comparative cross-species imaging study (bench/animal research design analogy, not clinical CEBM)
PubMed 10444351 · doi:10.1006/jhev.1999.0313
What was done
Investigators analyzed whole-brain MRI scans from 44 living primate subjects representing 11 anthropoid species. Image analysis software was used to calculate total brain volume, neocortical gray matter volume, cerebral white matter volume, and spinal cord cross-sectional area. Allometric regression analyses were performed to determine whether human neocortical size and prefrontal cortex folding deviate from nonhuman primate allometric trajectories, and whether white matter expansion outpaces gray matter growth across species.
What was found
The abstract reports no numerical values, effect sizes, confidence intervals, or statistical parameters. It qualitatively reports support for all three tested hypotheses: human neocortex size was significantly larger than expected for human brain size, human prefrontal cortex was significantly more convoluted than expected, and cerebral white matter volume increases outpaced neocortical gray matter volume increases across anthropoid primates.
Why it matters
This study provides comparative neuroimaging evidence that hominid brain evolution involved specific structural reorganization—specifically in neocortical scaling, prefrontal folding, and white matter expansion—rather than simple uniform volumetric growth.
Limits
The abstract provides zero quantitative metrics or statistical values. The sample size is small overall (44 subjects across 11 species, averaging 4 individuals per species), leaving potential vulnerability to individual variance and low power per taxon. Specific species included, scanning parameters, segmentation error rates, and demographic breakdowns (e.g., sex and age) are not described in the abstract.
Cited by
- context White matter makes up approximately 60% of the human brain, which is a higher proportion than in other species.