Biology subjects

Vayssiere, N.

Publications and source records attributed to Vayssiere, N..

3 recordsLinked to original sources

bioRxiv2025

Cortical Processing for the Vestibular and Visual Input of Egomotion in Macaque Monkeys: Separate Networks with Targeted Convergence

The integration of visual and vestibular inputs during egomotion is fundamental for both postural and navigational control. In the present study, we used functional magnetic resonance imaging (fMRI) in four macaque monkeys to investigate cortical activation in response to galvanic vestibular stimulation (GVS), applied through transmastoid electrodes, and egomotion-compatible (EC) optic flow patterns. Visual and vestibular stimulations activate two largely independent cortical networks: the vestibular network encompasses the insular cortex, superior parietal lobule, frontal lobe, and cingulate cortex, while optic flow primarily activates regions in the superior temporal sulcus, temporo-parietal junction, inferior parietal lobule, and restricted portions of the cingulate and frontal cortices. Despite this segregation, several areas exhibit visuo-vestibular convergence: VPS in the temporo-parietal junction, area 7 in the inferior parietal lobule, VIP and LIP in the intraparietal sulcus, MSTd in the superior temporal sulcus, CSv in the cingulate sulcus, and FEFsem in the frontal cortex. These findings demonstrate that visual and vestibular signals generated by egomotion are processed in extended and distinct cortical networks with several narrow convergence sites, consistent with the idea that multisensory integration during self-motion is achieved through selective convergence rather than general network overlap.

neuroscience↗

bioRxiv2025

Motion processing in visual cortex of maculopathy patients

Previous studies on animal models suggested that visual areas involved in motion processing could undergo important cortical reorganizations following retinal damages. This could have major implications for patients suffering from macular degeneration (MD), one leading cause of vision loss. Here, we performed fMRI recordings in a group of maculopathy patients (including individuals suffering from age-related macular degeneration or from Stargardts Disease) and a control group to characterize the motion processing cortical network in MD patients and determine whether this network is modified following the onset of the scotoma. We used an experimental protocol based on random-dot kinematograms (RDKs) classically employed to characterize motion-selective areas in the brain. To ensure that the visual information processed by the two groups was equivalent, the visual field in each control participant was masked using an artificial scotoma directly derived from clinical measurements in their paired patient. We found that in MD patients, translational motion elicited significant and robust activations in a restricted cortical network which included the human V5/MT+ complex (hMT+), areas V3A and V6, and a portion of primary visual areas (V1, V2 and V3) connected to peripheral vision. Importantly, the same patterns of responses were also observed in control participants. Moreover, the extent and strength of activation within these motion-selective areas did not differ significantly between the two groups. Altogether, these results suggest that in humans, the motion-selective network does not undergo significant large-scale cortical reorganizations following the onset of MD. Significance statementMotion processing in the visual cortex of patients with macular degeneration has never been characterized. Here, we performed fMRI recordings in 7 maculopathy patients and found robust motion-selective activations in a cortical network which included the human V5/MT+ complex (hMT+), areas V3A and V6, and a portion of primary visual areas connected to peripheral vision. These activations closely align with those reported in participants with normal vision in the literature and do not significantly differ from those measured in a group of age and gender-matched control participants who viewed the motion stimuli with a matched artificial scotoma. Altogether, our results suggest that the motion-selective network does not undergo significant large-scale reorganizations in maculopathy patients following the onset of the scotoma.

neuroscience↗

bioRxiv2024

Visuo-Vestibular Integration for Self-Motion: Human Cortical Area V6 Prefers Forward and Congruent Stimuli

BACKGROUNDThe integration of visual and vestibular input is crucial for self-motion. Information from both sensory systems merges early in the central nervous system. Among the numerous cortical areas involved in processing this information, some (V6 and VIP) respond specifically to vestibular anteroposterior information. OBJECTIVETo further understand the involvement of these and other areas in self-motion processing when vestibular and visual information are combined with varying congruence and direction parameters. METHODSFifteen subjects underwent an MRI session while receiving visual (optic flow patterns) and galvanic vestibular stimuli mimicking six conditions: (1) visual forward, (2) visual backward, visual forward with (3) congruent or (4) incongruent vestibular information, visual backward with (5) congruent or (6) incongruent vestibular information. RESULTSThe combination of concurrent vestibular stimulation and fully consistant optic flow patterns activated several bilateral cortical areas found predominantly in the insula. Among these vestibular areas and those previously defined in our initial study, the large majority do not show any specifity for the forward/backward direction or for the visuo-vestibular congruency. A notable exception was the parieto-occipital area V6, which showed a marked preference for congruent visuo-vestibular signals and for cues signaling forward motion. CONCLUSIONSBy showing that V6 is more active when visuo-vestibular signals are more ecological (i.e. when both signals specify the most common self-motion direction), our results support the view that this area plays a crucial role in visuo-vestibular integration during self-motion.

neuroscience↗