Biology subjects

Navarro Schroeder, T.

Publications and source records attributed to Navarro Schroeder, T..

3 recordsLinked to original sources

bioRxiv2026

Can grid cells produce hexadirectional signals?

Hexadirectional modulation is widely treated as a proxy for population-level grid-cell activity in humans. Here we show that this interpretation is generally not supported by the statistics of grid-cell firing. Conventional analyses test symmetric sixfold modulation of the mean response, whereas grid-cell firing predicts a dominant sixfold modulation of cell-level variance, rather than population-level mean. Using analytical deduction, simulations and a large-scale rodent dataset, we show that the previously reported mean hexadirectional effect is not a principal consequence of grid-cell activity. Among current hypotheses, a signal compatible with empirical rodent MEC cell population characteristics can emerge only with a second-order nonlinearity, and only under restricted conditions. Even then, the expected population-level mean modulation is small, approximately 2%. These findings suggest that the existing human literature targets a weak, indirect signature rather than a diagnostic readout of grid-cell population coding. Moreover, many reported hexadirectional effects may arise from testing a single sixfold component without establishing the full spectral response is robust against an appropriate null distribution. We provide a more comprehensive framework for testing hexadirectional symmetry in future studies.

neuroscience↗

bioRxiv2019

Behavior-dependent directional tuning in the human visual-navigation network

The brain derives cognitive maps from sensory experience that guide memory formation and behavior. Despite extensive efforts, it still remains unclear how the underlying population activity relates to active behavior and memory performance. To examine these processes, we here combined 7T-fMRI with a kernel-based encoding model of virtual navigation to map world-centered directional tuning across the human cortex. First, we present an in-depth analysis of directional tuning in visual, retrosplenial, parahippocampal and medial temporal cortices. Second, we show that tuning strength, width and topology of this directional code during memory-guided navigation depend on successful encoding of the environment. Finally, we show that participants locomotory state influences this tuning in sensory and mnemonic regions such as the hippocampus. We demonstrate a direct link between neural population tuning and human cognition and show that high-level memory processing interacts with network-wide environmental coding in the service of behavior.

neuroscience↗

bioRxiv2017

Optimal decision making using grid cells under spatial uncertainty

Minimizing spatial uncertainty is essential for navigation, but the neural mechanisms remain elusive. Here we combine predictions of a simulated grid cell system with behavioural and fMRI measures in humans during virtual navigation. First, we showed that polarising cues produce anisotropy in motion parallax. Secondly, we simulated entorhinal grid cells in an environment with anisotropic information and found that self-location is decoded best when grid-patterns are aligned with the axis of greatest information. Thirdly, when exposing human participants to polarised virtual reality environments, we found that navigation performance is anisotropic, in line with the use of parallax. Eye movements showed that participants preferentially viewed polarising cues, which correlated with navigation performance. Finally, using fMRI we found that the orientation of grid-cell-like representations in entorhinal cortex anchored to the environmental axis of greatest parallax information, orthogonal to the polarisation axis. In sum, we demonstrate a crucial role of the entorhinal grid system in reducing uncertainty in representations of self-location and find evidence for adaptive spatial computations underlying entorhinal representations in service of optimal navigation.

neuroscience↗