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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - DecodeRemapping (Decoding the neural mechanism of human spatial cognition using behavioural and hemodynamic signals)

Teaser

Summary

The aim of this project was to understand space constancy, that is the mechanisms used by the brain to build a stable and continuous percept of our environment despite frequent movements of our sensory receptors (eyes, ears). For example, each time we move our eyes, the image of the outside world sweeps across the retina, yet we see the world as stable. Studies using single cell recording in animals have shown that some visual neurons predict what the world will look like after an eye movement by remapping their receptive fields to the place they will occupy following the movement. By combining behavioral tools with fMRI imaging analysis, I aimed to determine the mechanisms our brains use to stabilize our percept of the world for visual and auditory objects.
This interdisciplinary project constituted a unique opportunity to link two strong and well developed scientific fields on a common question while giving me the chance to expend my skills and build a multifaceted profile of psychologist and neuroscientist.
The overall objectives were to determine on which mechanism this impression of space constancy relies and expend previous research towards more naturalistic environment including not only visual but also auditory and tactile stimulation.

Work performed

I first demonstrated using behavioral methods that every time we move our eyes, we predict the consequences of these movements. To do so, we estimated in advance where interesting objects will fall on the back of our eyes after the movement. This research led to a publication (Szinte et al., 2018, eLife) in which I took advantage of a new method to measure in human maps of the deployment of attention before a rapid eye movements.
Contrary to this first project which focused on visual mechanism, I next aimed at expanding the question of space constancy to the localization of sounds. Using only eye-tracking records, I found that oculomotor structures in charge of our eye movements represent sounds on visual maps. Moreover, these brain structures keep these sounds in an external reference frame by predicting the consequence of our movement (Szinte et al., under review in Current Biology).
The second part of the project involved the use of hemodynamical records using fMRI signals. In particular, I worked on developing a state-of-the-art methods to measure visuo-spatial information in the human visual cortex. Interestingly, while doing so, I encountered an unexpected finding, the fact that the default network (DN), a brain network with correlated activities spanning frontal, parietal and temporal cortical lobes displayed some typical and yet unknown visual organization (see attached Figure, Szinte & Knapen, submitted to Cerebral Cortex).
Finally, I applied these methods to the main project question and investigated the modulation of gaze direction on the representation of human visual field by means of hemodynamical records. I could find that both cortical, parietal and frontal nodes of the visual system only expressed a retinotopic organization which was not affected by the position of the eyes and this irrespective of whether attention was or wasnâ€™t devoted to the stimulus used to determine the visual system organization (Szinte et al., in preparation).

Final results

Together our results established the possibility to use both measured sensitivity and evoked hemodynamical activities to study to understand human prediction mechanisms at the core of our spatial vision. They establish that humans interact with their visual spatial environment through precise predictions operated by the attentional system. The 2 years of these projects allowed me to gain theoretical knowledge, scientific diversity, advanced methodological skills, students mentoring, communication skills and grant writing.
Because the proposed project was at the interface of experimental psychology and neuroscience, it allowed me to gain a unique multi-faceted profile of psychologists and neuroscientist. I established strong collaboration with the Vrije Universiteit and in particular the Spinoza Center for Neuroimaging in which Iâ€™m now an invited researcher. In these regards, my project allowed me to forge new connections and collaborations, enhanced the recognition of my supervisorsâ€™ department and university as well as the MSC Actions.
While the societal implications are rare, I demonstrate the possibility to combine two large and strong field of human cognition to improve our general knowledge of the human brain.