Search

Tract-tracing studies in primates indicate that different subregions of the medial temporal lobe (MTL) are connected with multiple brain regions. However, no clear framework defining the distributed anatomy associated with the human MTL exists. This gap in knowledge originates in notoriously low MRI data quality in the anterior human MTL and in group-level blurring of idiosyncratic anatomy between adjacent brain regions, such as entorhinal and perirhinal cortices, and parahippocampal areas TH/TF. Using MRI, we intensively scanned four human individuals and collected whole-brain data with unprecedented MTL signal quality. Following detailed exploration of cortical networks associated with MTL subregions within each individual, we discovered three biologically meaningful networks associated with the entorhinal cortex, perirhinal cortex, and parahippocampal area TH, respectively. Our findings define the anatomical constraints within which human mnemonic functions must operate and are insightful for examining the evolutionary trajectory of the MTL connectivity across species., Competing Interests: Declaration of interests The Max Planck Institute for Human Cognitive Sciences has an institutional research agreement with Siemens Healthcare. N.W. holds a patent on acquisition of MRI data during spoiler gradients (US 10,401,453 B2). N.W. was a speaker at an event organized by Siemens Healthcare and was reimbursed for the travel expenses., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Summary Grid cells are one of the core building blocks of spatial navigation [ 1 ]. Single-cell recordings of grid cells in the rodent entorhinal cortex revealed hexagonal coding of the local environment during spatial navigation [ 1 ]. Grid-like activity has also been identified in human single-cell recordings during virtual navigation [ 2 ]. Human fMRI studies further provide evidence that grid-like signals are also accessible on a macroscopic level [ 3–7 ]. Studies in both non-human primates [ 8 ] and humans [ 9, 10 ] suggest that grid-like coding in the entorhinal cortex generalizes beyond spatial navigation during locomotion, providing evidence for grid-like mapping of visual space during visual exploration—akin to the grid cell positional code in rodents during spatial navigation. However, electrophysiological correlates of the grid code in humans remain unknown. Here, we provide evidence for grid-like, hexadirectional coding of visual space by human high-frequency activity, based on two independent datasets: non-invasive magnetoencephalography (MEG) in healthy subjects and entorhinal intracranial electroencephalography (EEG) recordings in an epileptic patient. Both datasets consistently show a hexadirectional modulation of broadband high-frequency activity (60–120 Hz). Our findings provide first evidence for a grid-like MEG signal, indicating that the human entorhinal cortex codes visual space in a grid-like manner [ 8–10 ], and support the view that grid coding generalizes beyond environmental mapping during locomotion [ 4–6, 11 ]. Due to their millisecond accuracy, MEG recordings allow linking of grid-like activity to epochs during relevant behavior, thereby opening up the possibility for new MEG-based investigations of grid coding at high temporal resolution. Highlights • Hexadirectional modulation of human high-frequency electrophysiological activity • Grid-like mapping of visual space in the human entorhinal cortex • Grid-coding beyond environmental mapping during locomotion Staudigl et al. show grid-like modulation of human high-frequency activity in non-invasive magnetoencephalographic and intracranial EEG recordings. The results indicate that the human entorhinal cortex codes visual space in a grid-like manner, supporting the view that grid coding generalizes beyond environmental mapping during locomotion. [ABSTRACT FROM AUTHOR]