Is the middle cranial fossa a reliable predictor of temporal lobe volume in extant and fossil anthropoids?

Abstract

ObjectivesWe investigate the suitability of middle cranial fossa (MCF) size as a proxy for temporal lobe volume (TLV), examining the strength of the association between TLV and MCF metrics and assess the reliability predicting TLV in fossil anthropoids. The temporal lobe of the primate brain is a multimodal association cortex involved in long‐term memory, auditory, and visual processing with unique specializations in modern humans for language comprehension. The MCF is the bony counterpart for the temporal lobe providing inferences for fossil hominin temporal lobe evolution. We now investigate whether the MCF is a suitable proxy for the temporal lobe.MethodsA sample of 23 anthropoid species (n = 232, including 13 fossil species) from computed tomography (CT) scans of ex vivo crania and magnetic resonance imaging (MRI) of the in vivo brain were generated into three‐dimensional (3D) virtual models. Seven linear metrics were digitally measured on the right MCF with right TLV calculated from in vivo MRI.ResultsRegression analyses produced statistically significant correlations between TLV and all MCF metrics (r ≥ 0.85; p ≤ 0.0009) with TLV predictions within ±1 standard error and three MCF metrics (posterior‐width, mid‐length, and mid‐width) the most reliable predictors of TLV with only one metric weakly associated with TLV.DiscussionThese findings indicate a strong association between the MCF and TLV, provide reliable predictors of fossil TLV that were previously unattainable, allow the inclusion of fragmentary fossil material, and enable inferences into the emergence of modern human temporal lobe morphology.

A network approach to the topological organization of the Brodmann map

“…In particular, the superior temporal gyrus has high values for most of the centrality measures, evidencing that it is embedded in a complex morphological frame. The temporal cortex is supposed to have many derived features in humans (Bastir et al, 2008; Bryant & Preuss, 2018; Pearson et al, 2020), but its topological condition suggests caution when making inference on its macroscopic anatomical variations. Also the supramarginal gyrus and the pericentral regions are susceptible of indirect spatial influences, and variations of their morphology should be considered within a more general topological view.…”

Updated imaging and phylogenetic comparative methods reassess relative temporal lobe size in anthropoids and modern humans

“…The Pearson Sample used voxel‐based volumetric calculation directly from the MRI without interpolation estimation conducted in Brainsuite 17a (Shattuck & Leahy, 2002) following automatic segmentation for H. sapiens (Figure 1) and manual segmentation for non‐human anthropoids as per Pearson et al (2020). In the Pearson sample, intraobserver error was estimated an analysis of variance (ANOVA) as the proportion of the mean‐squared differences between replicates relative to the total between‐group variation (Bailey & Byrnes, 1990).…”

“…The extrapolation of MCF shape changes in fossil Homo were used to infer key evolutionary changes to the temporal lobe shape (Bastir et al, 2008; Bastir et al, 2011) and sulcal pattern evolution (Rosas et al, 2014). However, the temporal lobe and MCF estimates were not statistically assessed until recently when Pearson et al (2020) proposed a predictive equation for temporal lobe volume (TLV) from the MCF in fossil and living anthropoids including fossil hominins.…”