Larger Relative Volume of Frontal Lobe White Matter

The human frontal lobe has evolved a relatively large amount of underlying white matter.  A comparative volumetric MRI study by Schoenemann et al. (2005) reported that the amount of white matter under the human prefrontal cortex exceeded allometric predictions for an anthropoid primate of the same non-prefrontal white matter volume.  This conclusion has been questioned because of problems with the anatomical segmentation of prefrontal cortex from MRI across different species and because human prefrontal white matter was shown to closely fit allometric expectations for prefrontal gray matter (Sherwood et al., 2005). Interestingly, however, Schenker et al. (2005) showed that humans have relatively more gyral white matter in the frontal lobe than expected for an ape with the same frontal lobe “core” white matter.