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Leelaarporn, P.

Publications and source records attributed to Leelaarporn, P..

6 recordsLinked to original sources

bioRxiv2026

Blindness reshapes mental time travel: From perceptual scenes to conceptual scaffolds

How can humans remember and imagine without vision? Mental time travel, the ability to re-experience past events and envision future ones, is widely assumed to rely on visual imagery and the construction of mental scenes. Blindness provides a critical test of this assumption. Across behavioral interviews, language analyses, and multimodal neuroimaging in congenitally blind, late-blind, and sighted individuals, we show that blind individuals, even those blind from birth, mentally time travel as vividly as sighted people, but construct their inner worlds differently. Sighted participants relied on perceptual detail and activated classic scene-processing regions, whereas blind participants emphasized thoughts and emotions and recruited reorganized occipital cortex. Connectivity analyses revealed strengthened coupling between occipital and medial temporal regions, indicating adaptive reconfiguration of the episodic system. The brain does not require images to imagine: it flexibly builds internal experiences using the representational resources available. Summary ParagraphHow humans reconstruct events that are no longer available to the senses is a fundamental but unresolved question. Remembering the past and imagining the future, known as mental time travel, is a defining feature of human cognition, shaping identity and guiding decisions{superscript 1},{superscript 2}. Prevailing theories assume that such constructions depend on visual imagery, with the minds eye reconstructing events on a visuospatial stage3,. Blindness provides a critical test of this assumption. Across extensive behavioral interviews and multimodal neuroimaging, we find that mental time travel remains phenomenologically intact in blindness, but its scaffolding changes fundamentally. Sighted individuals rely on perceptual detail and activate regions specialized for visual scenes, whereas blind individuals, whether blind from birth or later in life, emphasize thoughts and emotions and reorganize occipital cortex for conceptual strategies,. These contrasting strategies map onto distinct neural signatures, revealing a dissociation between perceptual and conceptual routes to episodic simulation. Together, these findings reveal that the brains capacity to construct internal experience rests on conceptual scaffolding, not perceptual re-creation.

neuroscience↗

bioRxiv2025

Seeing more than schemas: the vmPFC represents imagery- rich mental scenarios

Mental imagery varies dramatically across individuals, from vivid scene construction to the complete absence of visual experience, as seen in aphantasia. While the ventromedial prefrontal cortex (vmPFC) is traditionally associated with abstract, schematic representations, emerging theories suggest it may also contribute to constructing vivid, visual mental content. To test this, we developed a novel 7T fMRI experiment varying imagery demands across conditions: Prior to scanning, participants memorized richly detailed scenarios, more constrained, stationary objects, and finally semantic definitions for each of three abstract German words (e.g., hope). During fMRI and eye-tracking, the same word was presented across trials, but participants vividly re-engaged with one of three distinct representations (i.e., scenarios, objects, and definitions), allowing for comparison across richly different cognitive modes triggered by identical visual input. Univariate analyses confirmed previous findings; highlighting the roles of the vmPFC, hippocampus, parahippocampal cortex, and visual-perceptual cortex in imagery-rich scenario construction. We further performed multivoxel pattern analysis (MVPA) to examine distributed neural representations, which can reveal the informational content of mental imagery beyond activation magnitude. Critically, the vmPFC was the only brain region where MVPA classifier accuracy was higher for scenario construction than for object and abstract conditions, directly supporting our hypothesis that the vmPFC encodes imagery-rich details rather than solely abstract, schematic information. Eye movement variability also distinguished between conditions. These findings advance our understanding of vmPFC function, emphasising its role in representing vivid mental content. HighlightsO_LI{middle dot} vmPFC distinctly represents imagery-rich scenarios in MVPA analysis C_LIO_LIUnivariate fMRI reveals increased HC and PHC activity during scenario construction C_LIO_LIEye movements vary by imagery type, distinguishing scenarios from objects and definitions C_LI

neuroscience↗

bioRxiv2025

Elucidating directed neural dynamics of scene construction across memory and imagination

Autobiographical memory (AM) and imagination both rely on the brains ability to construct vivid, coherent mental representations of past or imagined experiences. A central cognitive process underlying these functions is scene construction--the mental generation of spatially organized, imagery-rich representations of environments. Using ultra-high field 7T fMRI combined with Dynamic Causal Modeling (DCM), we examined directed effective connectivity among key nodes of the default mode network: the ventromedial prefrontal cortex (vmPFC), hippocampus, and precuneus during object imagery, single-scene construction, and AM retrieval. Our results revealed distinct patterns of network dynamics depending on task demands. During AM retrieval, effective connectivity was characterized by vmPFC-driven top-down modulation primarily targeting the precuneus, supporting the temporal and self-relevant structuring of episodic memory. In contrast, extended scenario imagination engaged hippocampal bidirectional influences with both vmPFC and precuneus, reflecting the dynamic simulation and integration of unfolding events. Single Scene construction shifted network leadership to the precuneus, which exerted modulatory effects on both vmPFC and hippocampus, consistent with its pivotal role in spatial integration and the generation of coherent mental scenes. Object imagery showed minimal stable connectivity within this network, suggesting limited engagement of the hippocampal-default mode circuit during simpler visual representations. Together, our findings highlight a flexible, task-dependent reorganization of effective connectivity within the vmPFC- hippocampus-precuneus network during the construction of rich mental experiences. Scene construction emerges as a unifying mechanism linking memory and imagination, with the direction and strength of neural interactions adapting according to whether temporal or spatial demands predominate. HighlightsO_LIAutobiographical memory is reflected by vmPFC-driven effective connectivity C_LIO_LIEffective connectivity varies flexibly amongst vmPFC, hippocampus and precuneus C_LIO_LIScene construction emerges as a core process across memory and imagination C_LI

neuroscience↗

bioRxiv2025

From single scenes to extended scenarios: the role of the ventromedial prefrontal cortex in the construction of imagery-rich events

Mental events are fundamental to daily cognition, including the recollection of past experiences, the anticipation of future scenarios, and engagement in imaginative, fictitious thought. Typically, these temporally extended mental events unfold within coherent spatial contexts, rich in naturalistic scenes and objects. However, there remains a significant gap in understanding how these events are represented in the brain. This study aimed to investigate the neural patterns involved in the construction of temporally extended mental events. Using ultra-high field functional magnetic resonance imaging, we examined brain regions previously implicated in this cognitive process, including the ventromedial prefrontal cortex (vmPFC), hippocampus, and posterior neocortex. We employed a novel experimental paradigm in which participants engaged in three forms of mental imagery: single objects (e.g., "a black espresso"), single scenes (e.g., "a busy cafe"), and extended scenarios (e.g., "meeting a friend for coffee"). We identified a shared neural network - comprising the vmPFC, hippocampus, and posterior neocortex - engaged across all forms of mental imagery. However, we observed a hierarchical organization in their contributions: the posterior neocortex supported the construction of objects, scenes, and scenarios, while the hippocampus primarily contributed to scenes and scenarios. The vmPFC exhibited a stepwise increase in activation, peaking during scenario construction. These findings suggest that the construction of mental events emerges from the close interaction of perceptual details provided by the posterior neocortex, spatial coherence from the hippocampus, and the integration of those elements into a coherent, temporally extended mental event by the vmPFC - the "movies" of the mind.

neuroscience↗

bioRxiv2023

Hippocampal-occipital connectivity reflects autobiographical memory deficits in aphantasia

Aphantasia refers to reduced or absent visual imagery. While most of us can readily recall decade-old personal experiences (autobiographical memories, AM) with vivid mental images, there is a dearth of information about whether the loss of visual imagery in aphantasics affects their AM retrieval. The hippocampus is thought to be a crucial hub in a brain-wide network underlying AM. One important question is whether this network, especially the connectivity of the hippocampus, is altered in aphantasia. In the current study, we tested 14 congenital aphantasics and 16 demographically matched controls in an AM fMRI task to investigate how key brain regions (i.e., hippocampus and visual-perceptual cortices) interact with each other during AM re-experiencing. All participants were interviewed regarding their autobiographical memory to examine their episodic and semantic recall of specific events. Aphantasics reported more difficulties in recalling AM, were less confident about their memories, and described less internal and emotional details than controls. Neurally, aphantasics displayed decreased hippocampal and increased visual-perceptual cortex activation during AM retrieval compared to controls. In addition, controls showed strong negative functional connectivity between the hippocampus and the visual cortex during AM and resting-state functional connectivity between these two brain structures predicted better visualization skills. Our results indicate that visual mental imagery plays an important role in detail-rich vivid AM, and that this type of cognitive function is supported by the functional connection between the hippocampus and the visual-perceptual cortex.

neuroscience↗

bioRxiv2022

Hippocampal subfields and their neocortical interactions during autobiographical memory using submillimeter whole-brain fMRI at 7 Tesla

Advances in ultra-high field 7 Tesla functional magnetic resonance imaging (7T fMRI) have provided unprecedented opportunities to gain insights into the neural underpinnings supporting human memory. The hippocampus, a heterogeneous brain structure comprising several subfields plays a central role during vivid re-experiencing of autobiographical memories (AM). However, due to technical limitations, how hippocampal subfields differentially support AM, whether this contribution is specific to one portion along the hippocampal long-axis, and how subfields are functionally connected with other brain regions typically associated with AM retrieval remains elusive. Here, we leveraged technical advances of parallel imaging and employed a submillimeter Echo Planar Imaging sequence over the whole brain while participants re-experienced vivid, detail-rich AM. We found that all hippocampal subfields along the long-axis were engaged during AM retrieval. Nonetheless, only the pre/parasubiculum within the anterior body of the hippocampus, contributed over and above to AM retrieval. Moreover, whole-brain functional connectivity analyses of the same data revealed that this part of the hippocampus was the only one that was strongly connected to other brain regions typically associated with AM, such as the ventromedial prefrontal cortex (vmPFC) and medial/lateral parietal regions. In the context of the broader literature, our results support recent proposals that the anterior body of the pre/parasubiculum may play an essential role in scene-based cognition, such as the re-experience of personal past events. HighlightsO_LIAll hippocampal subfields differentiate AM retrieval from mental arithmetic problem solving C_LIO_LIThe anterior body of the pre/parasubiculum engages in AM more than other subfields C_LIO_LIThe anterior body of the pre/parasubiculum is strongly connected to the AM network C_LIO_LIThe pre/parasubiculum may be preferentially involved in scene-based cognition C_LI

neuroscience↗