Abstract
The mesiotemporal lobe (MTL) is implicated in many cognitive processes, is compromised in numerous brain disorders, and exhibits a gradual cytoarchitectural transition from six-layered parahippocampal isocortex to three-layered hippocampal allocortex. Leveraging an ultra-high-resolution histological reconstruction of a human brain, our study showed that the dominant axis of MTL cytoarchitectural differentiation follows the iso-to-allocortical transition and depth-specific variations in neuronal density. Projecting the histology-derived MTL model to in-vivo functional MRI, we furthermore determined how its cytoarchitecture underpins its intrinsic effective connectivity and association to large-scale networks. Here, the cytoarchitectural gradient was found to underpin intrinsic effective connectivity of the MTL, but patterns differed along the anterior-posterior axis. Moreover, while the iso-to-allocortical gradient parametrically represented the multiple-demand relative to task-negative networks, anterior-posterior gradients represented transmodal versus unimodal networks. Our findings establish that the combination of micro- and macrostructural features allow the MTL to represent dominant motifs of whole-brain functional organisation.
Highlights
We developed a detailed model of the confluence of cortical types in the parahippocampus-hippocampus complex based on an 40 mm 3D histological reconstruction of a human brain, which we translated to in-vivo functional imaging and macroscale connectomics
Considering mesiotemporal lobe (MTL) cytoarchitecture, we observed a strong gradient along the iso-to-allocortical axis, with depth-wise intracortical profiles acting as robust predictors of spatial axis location
We found that the iso-to-allocortical and anterior-to-posterior axes differentially contributed to distinct dimensions of macroscale functional systems, with anterior-to-posterior position reflecting trade-offs between sensory and transmodal
Summary
The mesiotemporal lobe (MTL) is implicated in a diverse range of cognitive processes, notably memory, navigation, socio-affective processing, and higher-order perception (Moscovitch et al, 2005; Squire et al, 2004; Zheng et al, 2017; Milner, 2005; Eichenbaum et al, 2007; Wang et al, 2018; Eacott et al, 1994; Lee and Rudebeck, 2010; Buzsaki and Moser, 2013; Felix-Ortiz and Tye, 2014; Lech and Suchan, 2013). Neuroscience plays in human cognition emerges through interactions between neural codes within the MTL and the rest of the brain (Lech and Suchan, 2013; Saksida and Bussey, 2010; Staresina and Davachi, 2009; Diana et al, 2007). A widely held assumption posits that the broad role of the MTL in human cognition results from both its intrinsic circuitry and position within the larger cortical architecture, which places the MTL at the apex of multiple conceptual hierarchies (Mesulam, 1998; Felleman and Van Essen, 1991; Chanes and Barrett, 2016)
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