Biology subjects

Ramanoël, S.

Publications and source records attributed to Ramanoël, S..

5 recordsLinked to original sources

bioRxiv2023

Age-related disparities in oscillatory dynamics within scene-selective regions during spatial navigation

Position is a key property that allows certain objects in the environment to attain navigational relevance. Symmetrical processing of object position across the horizontal meridian remains an unchallenged assumption of the spatial navigation literature. Nonetheless, a growing body of research reports vertical inhomogeneities in perceptual tasks, and recent evidence points towards a lower visual field preference in healthy aging. Factoring in the vertical position of objects to better apprehend spatial navigation abilities across the lifespan is essential. The occipital place area (OPA), parahippocampal place area (PPA), and medial place area (MPA) are ideal candidates to support the processing of the vertical location of navigational cues. Indeed, they are implicated in scene processing and spatial cognition, functions that may interact with their underlying retinotopic codes. This study aimed to elucidate whether young and older participants adjusted their gaze patterns and EEG activity within scene-selective regions in response to the vertical arrangement of landmarks. A sample of 21 young and 21 older participants completed a desktop-based task requiring them to navigate using objects at different vertical locations. We equipped them with an eye tracker and a high-density EEG cap. We used a fMRI-informed source-reconstruction algorithm to study the OPA, PPA and MPA with high spatial and temporal precision. Older adults exhibited a higher number of errors compared to young adults during reorientation. This age-related decline in accuracy was accompanied by a tendency among older participants to fixate objects in the lower half of the screen. This gaze bias was absent in young participants, who instead adapted their oculomotor behaviour based on the position of navigationally-relevant information. Another primary finding pertains to the differential pattern of theta and beta band activity in the OPA, PPA and RSC for environments that only contained relevant cues in the upper visual field. It thus appears that scene-selective regions process some aspect of the vertical position of information, irrespectively of their inherent retinotopic biases. Moreover, we revealed striking disparities between age groups in beta/gamma band synchronization in all scene-selective regions, indicating compromised top-down attentional mechanisms during spatial navigation in ageing. These age-related disparities in attentional dynamics might account for performance deficits in older participants. This study sheds light on a systematic downward gaze bias and altered attentional dynamics within scene-selective regions during spatial navigation in older age. It also emphasises the importance of considering vertical positioning as a fundamental property of objects within scenes.

neuroscience↗

bioRxiv2022

The vertical position of visual information conditions spatial memory performance in healthy aging

Memory for objects and their location is a cornerstone of adequate cognitive functioning across the lifespan. Considering that human visual perception is dependent upon the position of stimuli within the visual field, we posit that the position of objects in the environment may be a determinant aspect of mnemonic performance. In this study, a population of young and older adults completed a source monitoring task with objects presented either in the upper or lower visual field. Using multinomial processing tree modeling, we revealed that while item memory remained intact in older age, spatial memory was impaired but only for objects that had been presented in the upper visual field. Spatial memory is therefore conditioned by the vertical position of information. These findings put into question the traditional view that age-related spatial mnemonic deficits are primarily attributable to high-order associative dysfunctions and suggest that they could also originate from altered encoding of object attributes.

neuroscience↗

bioRxiv2021

Selective neural coding of object, feature, and geometry spatial cues in humans

Orienting in space requires the processing and encoding of visual spatial cues. The dominant hypothesis about the brain structures mediating the coding of spatial cues stipulates the existence of a hippocampal-dependent system for the representation of geometry and a striatal-dependent system for the representation of landmarks. However, this dual-system hypothesis is based on paradigms that presented spatial cues conveying either conflicting or ambiguous spatial information and that amalgamated the concept of landmark into both discrete 3D objects and wall features. These confounded designs introduce difficulties in interpreting the spatial learning process. Here, we test the hypothesis of a complex interaction between the hippocampus and the striatum during landmark and geometry visual coding in humans. We also postulate that object-based and feature-based navigation are not equivalent instances of landmark-based navigation as currently considered in human spatial cognition. We examined the neural networks associated with geometry-, object-, and feature-based spatial navigation in an unbiased, two-choice behavioral paradigm using fMRI. We showed evidence of a synergistic interaction between hippocampal and striatal coding underlying flexible navigation behavior. The hippocampus was involved in all three types of cue-based navigation, whereas the striatum was more strongly recruited in the presence of geometric cues than object or feature cues. We also found that unique, specific neural signatures were associated with each spatial cue. Critically, object-based navigation elicited a widespread pattern of activity in temporal and occipital regions relative to feature-based navigation. These findings challenge and extend the current view of a dual, juxtaposed hippocampal-striatal system for visual spatial coding in humans. They also provide novel insights into the neural networks mediating object vs. feature spatial coding, suggesting a need to distinguish these two types of landmarks in the context of human navigation. Highlights O_LIComplex hippocampal-striatal interaction during visual spatial coding for flexible human navigation behavior. C_LIO_LIDistinct neural signatures associated with object-, feature-, and geometry-based navigation. C_LIO_LIObject- and feature-based navigation are not equivalent instances of landmark-based navigation. C_LI

neuroscience↗

bioRxiv2021

Mobile brain/body imaging of landmark-based navigation with high-density EEG

Coupling behavioral measures and brain imaging in naturalistic, ecological conditions is key to comprehend the neural bases of spatial navigation. This highly-integrative function encompasses sensorimotor, cognitive, and executive processes that jointly mediate active exploration and spatial learning. However, most neuroimaging approaches in humans are based on static, motion constrained paradigms and they do not account for all these processes, in particular multisensory integration. Following the Mobile Brain/Body Imaging approach, we aimed to explore the cortical correlates of landmark-based navigation in actively behaving young adults, solving a Y-maze task in immersive virtual reality. EEG analysis identified a set of brain areas matching state-of-the-art brain imaging literature of landmark-based navigation. Spatial behavior in mobile conditions additionally involved sensorimotor areas related to motor execution and proprioception usually overlooked in static fMRI paradigms. Expectedly, we located a cortical source in or near the posterior cingulate, in line with the engagement of the retrosplenial complex in spatial reorientation. Consistent with its role in visuo-spatial processing and coding, we observed an alpha power desynchronization while participants gathered visual information. We also hypothesized behavior-dependent modulations of the cortical signal during navigation. Despite finding few differences between the encoding and retrieval phases of the task, we identified transient time-frequency patterns attributed, for instance, to attentional demand, as reflected in the alpha/gamma range, or memory workload in the delta/theta range. We confirmed that combining mobile high-density EEG and biometric measures can help unravel the brain structures and the neural modulations subtending ecological landmark-based navigation.

neuroscience↗

bioRxiv2020

Differential brain activity in visuo-perceptual regions during landmark-based navigation in young and healthy older adults

Older adults exhibit prominent impairments in their capacity to navigate, reorient in unfamiliar environments or update their path when faced with obstacles. This decline in navigational capabilities has traditionally been ascribed to memory impairments and dysexecutive function whereas the impact of visual aging has often been overlooked. The ability to perceive visuo-spatial information such as salient landmarks is essential to navigate in space efficiently. To date, the functional and neurobiological factors underpinning landmark processing in aging remain insufficiently characterized. To address this issue, this study used functional magnetic resonance imaging (fMRI) to investigate the brain activity associated with landmark-based navigation in young and healthy older participants. Twenty-five young adults (=25.4 years, {sigma}=4.7; 7F) and twenty-one older adults (=73.0 years, {sigma}=3.9; 10F) performed a virtual navigation task in the scanner in which they could only orient using salient landmarks. The underlying whole-brain patterns of activity as well as the functional roles of scene-selective regions, the parahippocampal place area (PPA), the occipital place area (OPA), and the retrosplenial cortex (RSC) were analyzed. We found that older adults navigational abilities were diminished compared to young adults and that the two age groups relied on distinct navigational strategies to solve the task. Better performance during landmark-based navigation was found to be associated with increased neural activity in an extended neural network comprising several cortical and cerebellar regions. Direct comparisons between age groups further revealed that young participants had enhanced anterior temporal activity. In addition, young adults only were found to recruit occipital areas corresponding to the cortical projection of the central visual field during landmark-based navigation. The region-of-interest analysis revealed increased OPA activation in older adult participants. There were no significant between-group differences in PPA and RSC activations. These results hint at the possibility that aging diminishes fine-grained information processing in occipital and temporal regions thus hindering the capacity to use landmarks adequately for navigation. This work helps towards a better comprehension of the neural dynamics subtending landmark-based navigation and it provides new insights on the impact of age-related visuo-spatial processing changes on navigation capabilities.

neuroscience↗