Biology subjects

Delaux, A.

Publications and source records attributed to Delaux, A..

4 recordsLinked to original sources

bioRxiv2023

Age-related differences in electrophysiological correlates of visuospatial reorientation

Spatial navigation abilities decline with age. Recent studies revealed a specific impairment in landmark-based reorientation, linked to changes in scene-selective brain regions activity. While fMRI studies suggest that these cortical modulations might be compensatory, a more precise investigation of the brain dynamics associated with visuospatial processing is warranted. We analyzed Event-Related Potentials and Event-Related Spectral Perturbations recorded from electrodes over scene-selective regions. 28 young adults and 28 older adults completed a desktop-based reorientation task using landmarks. Our findings show poorer reorientation performance among older adults. Signatures of age-related modulation of EEG activity imputable to scene-selective regions were predominantly observed within the right hemisphere. EEG analysis disclosed a tripartite worsening of scene processing accounting for older adults difficulties. Firstly, a delayed and reduced P1 component likely reflects a slower and less efficient stimulus discrimination. Secondly, an increased N1 amplitude and theta-band activity suggest a higher demand on cognitive resources associated with more effortful processing of visuospatial information. Thirdly, a decreased P2 amplitude may imply deficient attentional mechanisms to select task-relevant stimuli.

neuroscience↗

bioRxiv2023

Scene-selective regions encode the vertical position of navigationally relevant information in young and older adulthood

Position within the environment influences the navigational relevance of objects. However, the possibility that vertical position represents a central object property has yet to be explored. Considering that the upper and lower visual fields afford distinct types of visual cues and that scene-selective regions exhibit retinotopic biases, it is of interest to elucidate whether the vertical location of visual information modulates neural activity in these high-level visual areas. The occipital place area (OPA), parahippocampal place area (PPA) and medial place area (MPA) demonstrate biases for the contralateral lower visual field, contralateral upper visual field, and contralateral hemifield, respectively. Interesting insights could also be gained from studying older adulthood as recent work points towards an age-related preference for the lower visual field. In the present study, young and older participants learned the position of a goal in a virtual environment that manipulated two variables: the vertical position of navigationally-relevant objects and the presence of non-relevant objects. Results revealed that all three scene-selective regions parsed the vertical position of useful objects independently of their subtending retinotopic biases. It therefore appears that representations in the higher-level visual system combined information about vertical position and navigational value for wayfinding purposes. This property was maintained in healthy aging emphasizing the enduring significance of visual processing along the vertical dimension for spatial navigation abilities across the lifespan.

neuroscience↗

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↗

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↗