Biology subjects

Sigismondi, F.

Publications and source records attributed to Sigismondi, F..

4 recordsLinked to original sources

bioRxiv2026

Eye movements reflect attentional navigation of number space without visual experience

Primates use eye movements to explore and gather information about their external, visual world. Similarly, even when there is nothing to see spontaneous eye movements reflect the structure and the exploration of internal, conceptual knowledge. However, it remains unclear what mechanism links eye movements to this internal search process. One possibility is that eye movements reflect visual imagery or visual exploration strategies used to explore conceptual knowledge. On the other hand, eye movements may reflect attentional movements in the conceptual space, which are independent from visual experience. Early blind individuals are a useful testbed for this hypothesis in that they never had access to functional vision, thus ruling out the influence of imagery or recycling of visual exploration strategies. To this end, we asked early blind individuals to perform a random number generation task while recording their eye movements. Using electrooculography (EOG), we found that eye movements track the exploration of the mental number line in both sighted and blind: participants moved their eyes to the right for positive changes in magnitude in the number sequence and to the left for negative changes, with eye movement amplitude scaling with the magnitude difference. Furthermore, sighted and early blind participants showed a similar temporal profile, with the effect peaking around 750 ms before number onset. These findings support the hypothesis that internally generated shifts of attention, rather than eye movements per se, drive the exploration of conceptual spaces.

neuroscience↗

bioRxiv2025

Spatial coding supports auditory conceptual navigation

Grid cells in human entorhinal cortex encode spatial layouts for real-world navigation, yet their role in conceptual navigation remains unclear. Here we show that mentally transforming tones within a purely auditory pitch-duration space engages spatial circuits, and that such resources are causally necessary. In Experiment 1, participants trained for five days to navigate through a purely conceptual pitch-duration auditory space, then underwent fMRI on Day 6. We observed a six-fold modulation of entorhinal BOLD signals aligned to each participants trajectory angles, similar to grid-cell firing in physical space. Stronger grid-like coding predicted larger training-related gains. In Experiment 2, a new cohort performed the same task under either a spatial or non-spatial interference load. Only the spatial condition selectively disrupted performance on trials requiring mental "movement," indicating a causal reliance on spatial resources. These findings provide evidence that auditory conceptual transformations recruit--and depend on--spatial grid-like computations in the entorhinal-hippocampal system, pointing to a domain-general role for spatial coding in organizing new knowledge along continuous dimensions.

neuroscience↗

bioRxiv2023

Altered grid-like coding in early blind people

Spatial navigation in humans relies heavily on vision. However, the impact of early blindness on the brain navigation network and on the hippocampal-entorhinal system supporting cognitive maps, in particular, remains elusive. Here, we tested sighted and early blind individuals in both imagined navigation in fMRI and real-world navigation. During imagined navigation, the Human Navigation Network was reliably activated in both groups, showing resilience to visual deprivation. However, neural geometry analyses highlighted crucial differences between groups. A 60{degrees} rotational symmetry, characteristic of grid-like coding, emerged in the entorhinal cortex of sighted but not blind people, who instead showed a 4-fold (90{degrees}) symmetry. Moreover, higher parietal cortex activity during navigation in the blind was correlated with the magnitude of 4-fold symmetry and real-word navigation abilities. In sum, early blindness can alter the geometry of entorhinal cognitive maps, possibly as a consequence of higher reliance on parietal egocentric coding during navigation.

neuroscience↗

bioRxiv2022

Supramodal Shape Representation in the Human Brain

We can sense an objects shape by vision or touch. Previous studies suggested that the inferolateral occipitotemporal cortex (ILOTC) implements supramodal shape representations as it responds more to seeing or touching objects than shapeless textures. However, such activation in the anterior portion of the ventral visual pathway could be due to the conceptual representation of an object or visual imagery triggered by touching an object. We addressed these possibilities by directly comparing shape and conceptual representations in early blind (who lack visual experience/imagery) and sighted participants. We found that bilateral ILOTC in both groups showed stronger activation during a shape verification task than during a conceptual verification task made on the names of the same manmade objects. Moreover, the distributed activity in the ILOTC encoded shape similarity but not conceptual association among objects. Besides the ILOTC, we also found shape representation in both groups bilateral ventral premotor cortices and intraparietal sulcus, a frontoparietal circuit relating to object grasping and haptic processing. In contrast, the conceptual verification task activated both groups left perisylvian brain network relating to language processing, and, interestingly, the cuneus in early blind participants only. The ILOTC had stronger functional connectivity to frontoparietal circuit than to the left perisylvian network, forming a modular structure specialized in shape representation. Our results conclusively support that the ILOTC selectively implements shape representation independently of visual experience, and this unique functionality likely comes from its privileged connection to the frontoparietal haptic circuit.

neuroscience↗