I received a Talent grant from the Amsterdam Brain and Cognition centre (ABC) in 2019 (125K euro) to investigate conscious perception using 7T fMRI and pharmacological interventions.

This project will be hosted by Simon van Gaal at the University of Amsterdam and we will work in close collaboration with Anouk Schrantee at Amsterdam University Medical Centre (AMC) and Serge Dumoulin and Tomas Knapen at the Spinoza Centre for Neuroimaging in Amsterdam.

Project description:

Influential theories of consciousness propose that "recurrent processing", the dynamic information exchange between brain regions, is crucial for consciousness. What is so special about recurrent processing that it should yield conscious perception? In this project we will explore the role of recurrent processing in conscious perception by administering Memantine, an uncompetitive NMDA antagonist, to healthy subjects. NMDA receptors are uniquely involved in recurrent but not feedforward processing. Blocking NMDA receptors will therefore interfere directly and specifically with recurrent processing.

In the first part of this project we will assess the influence of Memantine on basic characteristics of visual responses by measuring population receptive fields using 7T-fMRI. For each voxel we will determine the location and shape (e.g. size of center and surround) of the aggregate response selectivity of the neurons in that voxel. Additionally, participants will perform psychophysical experiments to test the influence of Memantine on the perception of several visual illusions. As the perception of illusions occurs without direct "bottom-up" support from the stimulus, we hypothesize that hampering recurrent processing will reduce illusion-strength and reduce the likelihood that illusions will occur.

In the second part of this project we will perform population receptive field mapping in separate layers of visual cortex (laminar fMRI) while participants perceive a visual illusion. The most feasible illusion for laminar fMRI will be selected based on the psychophysical results of the first part of the project. Feedforward signals primarily involve the middle layers in visual cortex, while recurrent processing mostly involves the deep and superficial layers. Therefore, we hypothesize that Memantine specifically reduces perception-related activity in deep/superficial layers and not in middle layers. By combining pharmacological interventions with state-of-the-art human neuroimaging techniques we aim to directly link the biochemical (neurotransmitters) with the system-level (brain regions) mechanisms underlying conscious perception.