Planum Temporale Cerebral Asymmetry

There is really no difference in PT asymmetry between humans and great apes.  Studies by Gannon and colleagues in post-mortem specimens and from in vivo scans by Cantalupo and Hopkins have shown that the leftward  PT asymmetry is present in all great apes though no systematic study has been done between ape species. More recently, Hopkins and Nir (2010) reported significant leftward asymmetries in the PT region for grey matter volumes and the magnitude of asymmetry was comparable to reports in human subjects. For both chimpanzees and humans, approimately 70% of the sample showed a significant leftward asymmetry.   In fossils, the PT cannot be quantified directly but indirectly, some have measured the length of the sylvian fissure and it is longer in the left compared to right hemisphere. Direct measures of sylvian fissure length have also been done in apes and they also show a leftward asymmetry.