Table of contents
- Auditory cognition
- Visuomotor adaptation in real life and in virtual reality
- Brain reorganisation, effects of prism adaptation and virtual reality
Auditory cognition
In 2001 we were one of the first groups to demonstrate in human subjects that auditory information pertaining to the meaning and to the location of a sound is processed along two anatomically distinct streams, since then referred to as the What and Where streams. Several of our 68 original papers on this topic had deep impact on the field, as e. g. Rivier and Clarke 1997, with over 720 citations, and Maeder et al. 2001, with over 400 citations.
Currents projects
More recently we focused on the processing of semantic information within the What stream, including neural plasticity involved in encoding newly acquired expertise. With 7T fMRI we have were able to disentangle how meaning, emotional valence and locations are encoded in early-stage auditory areas. Several of these more recent papers had deep impact on the field, as r. g. Da Costa et al. 2011, with over 240 citations.
The dual stream model of auditory processing posits partial separate processing for semantic and spatial information and yet percept is that of combined representations. In a series of experiments we shown that within the What stream a neuronal population is dedicated to encoding the meaning of sound objects together with their position in space. This position-linked representation plays a role in sound object segregation and auditory spatial attention. It relies heavily on the left hemisphere, in contrast to the well know right hemispheric dominance for explicit sound localization. In a recent 7T fMRI study, we have were able to disentangle how meaning, emotional valence and locations are encoded in early-stage auditory areas.
Visuomotor adaptation in real life and in virtual reality
Currents projects
We are examining the effects of a promising rehabilitation method that can alleviate cognitive deficits of patients with brain damage. This method, called “prism adaptation” has recently received much attention as a potential method for the rehabilitation of unilateral neglect symptoms in patients with right hemispheric damage. Following promising results, this method is more and more widely used on these patients, but there is still a lack of knowledge about the changes following such intensive training in neural networks underlying cognitive functions. In our project, we are using functional magnetic resonance imaging to investigate the effects of prism adaptation on the neural networks underlying attention, and spatial and verbal working memory in patients with right hemispheric damage and in control subjects.
Ultimately, the knowledge gained from this project will lead to a better understanding of the mechanisms and effects of PA, and to a more specific application of PA therapy. Considering the high prevalence of persistent spatial attention deficits in stroke patients, it is important to determine if a wider portion of brain damage patients can benefit from this non-invasive, non-expensive and easy to use method.
In this project, we use a new virtual reality (VR) based adaptation (VRA) based on a spatial displacement of the user’s visual experience in a head-mounted VR display, mimicking the adaptation done in real life via of prismatic goggles. The aim of this project is to determine if a visuo-motor adjustment developed during a pointing task in virtual reality induces similar behavioural and neural modulations than those observed after standard PA. This project is done in collaboration with MySpace lab (wp.unil.ch/myspacelab/).
Brain reorganisation, effects of prism adaptation and virtual reality
In a series of successful studies leading to seminal publications we showed how a therapeutic intervention targeting attention deficit changes the organization of the brain regions involved in attention processing in healthy subjects and in stroke patients and age-matched healthy subjects. The therapeutic intervention used in these studies, called prism adaptation (PA), is one of the main methods used to alleviate spatial attention deficits in stroke patients.
Our studies determined the mechanisms behind this intervention, and further provided biomarkers based on the location of the lesions, to determine patients who will be good responders to this intervention. An important, but surprisingly under-explored, field in this domain concerns the dynamic interaction between brain networks in stroke patients, and how this interaction is modulated by therapeutic interventions. In healthy subjects, we showed that the cognitive therapeutic intervention using prism adaptation changes the interplay between attentional networks. Attention deficits after stroke are known to be proportional to the disruption of the networks underlying attention, however, how therapeutic interventions change the interaction between these networks remains to be determined and is one of the main topic of our projects.
Currents projects
Childhood is a period of considerable changes in the anatomy and connectivity of the brain including the regions underlying attention. Alertness is developed during the first months of life. Orienting includes the ability to detect spatial targets that develops between 6-9 months and the voluntary orientation of attention is developed between 6-8 years old. The executive control of attention reaches full maturity in the second decade of life.
The aim of our project is to investigate the effect of a visuomotor adaptation task in virtual reality (VR) on three attentional networks (alertness, orienting, executive control of attention) in normal children (7 to 14 years old). We showed that, in neurotypical children, the visuomotor adaptation leads to an increase of activation in the parietal and frontal lobes during alertness and orienting. The location of these modulations are similar to those observed in our previous findings on adults.
