The human brain has been considered to have strong functional lateralisation where language is dominant in the left hemisphere and visuospatial functions in the right hemisphere (REfs). This strict dichotomy has been challenged repeatedly by clinical data and individual patients (REfs). In addition, studies looking at language recovery after stroke indicated a dynamic shift in functional activation during recovery (Saur et al. 2006).
We, therefore, used structural and functional data from the Human Connectome Project (www.humanconnectomeproject.com) to study functional activation in both hemispheres using a naturalistic viewing task that showed Hollywood movie snippets to the participants.
In a first step, we parcellated the left and right hemispheres using the Atlas of Intrinsic Connectivity of Homotopic Areas (AICHA), a functional brain ROIs atlas developed by the host, Group d’imagerie neurofunctional (GIN) at the University of Bordeaux (
https://www.gin.cnrs.fr/en/tools/aicha/(s’ouvre dans une nouvelle fenêtre)).
Second, a time point of the fMRI was taken and for each voxel, a t-test was conducted across the whole study cohort. This analysis resulted in a t-map of the brain for that specific time point. This process was repeated for all time points in the fMRI resulting in a fine-grained 1-sec segmentation of the data. The result is a 4D volume (i.e. 3D plus time dimension) of the t-values across all healthy participants. From this 4D volume, the activation and deactivation that are common across the volunteers at a given time point can be extracted. Building on this innovative approach, we projected the functional activations on the cortical surface and matched the activation with each second of the movie. The results can be viewed as a movie and as individual sequences (see Figure 1). Adjusting the hemodynamic delay, we mapped the functional activations to the movie sequences that elicited them.
Putting these results together, we have mapped a comprehensive model of brain lateralisation across functions (e.g. language, visuospatial, motor), brain regions, and its dynamic course across time (WP1).
The statistical analysis of the functional time series and across brain areas has revealed that activation variability is linked with lateralisation. The results have shown that functional activation dynamically shifts to each hemisphere depending on the movie input (WP1). This is a groundbreaking finding that will have far-reaching implications.
In preparation for WP2 and 3, I summarised the literature on white matter connection variability and cognitive-clinical variability (Forkel et al., 2022). The conceptual shift from single cases to studying the white matter disconnection studies was published as a book chapter (Forkel, 2022). My integration into the host department has led to several co-publications .
During the first year of PERSONALISED, I disseminated the project and its results as MSCA ambassador for the European Research Night (24/09/2021) and 12 invited talks at international laboratories or conferences. In line with the project proposal, I organised an international workshop on ‘Brain anatomy - theories, methods, applications' that is freely available online through my Clinical Neuroanatomy Seminar YouTube channel (
https://www.youtube.com/c/ClinicalNeuroanatomySeminars(s’ouvre dans une nouvelle fenêtre)). On this channel, we also made several tutorials available to foster a mutual transfer of skills between the host and the awardee and have a wider impact on the community.
