No spatially selective place cells contrasts emergent evidence for early novelty gist-like conceptual encoding in the human medial temporal lobe.

The 2014 Nobel prize was awarded to O’Keefe, Moser & Moser for discovering spatially allocentric encoding place and grid cell within the murine medial temporal lobe. Contrastingly, in equivalent structures, human concept cells respond to high-level abstract encodings such as ‘Jennifer Aniston’, independent of scale, angle, context, luminosity - regardless of location. Presently, some sparse studies indicate a presence of human place cells. This research aims to ratify those claims, akin to our supposedly archetypal murine models with highly spatially constrained ‘place cells’. Secondarily, emergence of concept cells is entirely undocumented in humans, and herein, undertaken. Epileptic volunteers undergoing curative surgery receiving intracranial electroencephalography implant were placed in head-mounted virtual experiments. Participants virtually foraged for coins in enclosures. Place cells were assessed through permutation methods including information theory, sparsity, intra-experimental place stability, naïve Bayesian decoding, and replicating a criterion presented by one lab as evidence of place cells. Across 6 patients, 723 neurones were recorded: not a single substantial place cell was observed, reflected in multiple inconsistent population metrics. Further, this contrasted against artificially simulated place cells, all despite participants behavioural learning. This indicated that human hippocampal spatial encodings may not be as robust as previously thought. Separately, subjects entered highly sensory-controlled, non-navigable, passively narrated experiences of digital characters in ambient environments. Participants were required to retain conceptual episodic information, with novel neural concept encoding appraised through baseline-stimulus firing criterion and parametricity. Population responses were poor, but some units indicated broader temporal firing profile units relative to established concept cells, which stereotypically exhibit highly repeatable firing onsets. In reflection, as a caveat, this study, suffered an internal replicability issue. Based upon these studies findings, principally lacking human place cells, original contributions to knowledge are theorised – naturally converging increasingly disjunctive spatial murine and abstract primate hippocampal literatures.