Neuroimaging
In the team, we use various neuroimaging methods, both in healthy participants and patient studies. Here is an overview.
Magnetic resonance imaging (MRI)
Functional MRI (fMRI)
Functional MRI is used in the team mainly in healthy participants to investigate the neural bases of high-level cognitive functions. Participants complete behavioral experiments while undergoing an fMRI acquisition and we then analyze the data by looking at differences of brain activity between conditions, or correlations of brain activity with experimental variables (parametric modulation).
Here is an example of a study from the lab in which we used fMRI:
Here is an example of a study from the lab in which we used functional connectivity in fMRI:
Resting-state MRI (rsMRI)
Resting-state MRI corresponds to the recording of the BOLD signal while participants are lying down in the scanner and asked to do nothing. This type of recording is mainly used in the lab to investigate the functional connectivity of the brain.
We investigate healthy brain connectivity patterns and functional connectivity of frontal brain regions. We also compare those brain connectivity patterns to the ones recorded in patients with frontal pathologies.
Diffusion tensor imaging (DTI)
Diffusion tensor imaging (DTI) is a type of magnetic resonance imaging (MRI) technique that allows for the visualization of the white matter tracts in the brain. It works by measuring the diffusion of water molecules in brain tissue, which can provide information about the structural integrity and organization of white matter fibers.
DTI generates a "tensor" that describes the direction and magnitude of water diffusion in each voxel of the brain. This tensor can be used to create color-coded maps of the brain's white matter tracts, which can help us to better understand the connectivity between different brain regions.
DTI has a variety of applications in both research and clinical settings. For example, it can be used to investigate changes in white matter integrity associated with neurological disorders, or to study the development of white matter connectivity during childhood and adolescence. DTI can also be used in neurosurgery planning, where it can help identify the location of important white matter tracts that need to be preserved during surgery.
Lara Migliaccio is the lab reference person for DTI.
Brain morphometry
Under construction
Example of publication in healthy individuals:
Electro-encephalography (EEG)
Intracranial EEG
In an effort to bridge across techniques and species, we investigate the human brain with intracranial electroencephalography (iEEG), which gives access to local field potentials in deep structures of the human brain. Thus, iEEG recordings avoid the attenuation and spatial diffusion of electrical signals that are collected with scalp electrodes. In addition, contrary to hemodynamic signals recorded using fMRI, they offer much better temporal resolution (milliseconds rather than seconds).
Such recordings can be obtained in patients being treated for drug-resistant focal epilepsy, who are implanted with intracranial electrodes for up to 2 weeks before surgery. This period provides a unique window into iEEG dynamics during performance of cognitive tasks in humans.
Alizée Lopez-Persem, Julien Bastin, Mathilde Petton, Raphaëlle Abitbol, Katia Lehongre, Claude Adam, Vincent Navarro, et al. « Four Core Properties of the Human Brain Valuation System Demonstrated in Intracranial Signals ». Nature Neuroscience 23, no 5 (mai 2020): 664‑75. https://doi.org/10.1038/s41593-020-0615-9.
Maëlle Gueguen, Alizée Lopez-Persem, Pablo Billeke, Jean-Philippe Lachaux, Sylvain Rheims, Philippe Kahane, Lorella Minotti, Olivier David, Mathias Pessiglione, et Julien Bastin. « Anatomical Dissociation of Intracerebral Signals for Reward and Punishment Prediction Errors in Humans ». Nature Communications 12, no 1 (7 juin 2021): 3344. https://doi.org/10.1038/s41467-021-23704-w.
Intra-operative cognitive mapping
Diffuse low-grade glioma are slowly growing tumors. The diagnosis is made after a first seizure, in a young adult with a normal socio-professional life. Surgery is the first line of treatment, as it has been demonstrated that the larger the resection, the better the survival. However, the extent of resection should be tailored according to each tumor location and patient's way of life, so that patients could resume the same life as before. To this end, the best methodology is to awake the patient in order to monitor continuously his cognitive and sensori-motor abilities and to perform brain mapping with electrical stimulation, allowing to detect critical areas that should not be resected. All the patients undergo, both before and after the surgery, and as a standard of clinical practice, extensive cognitive evaluations, as well as advanced MRI sequences of functional and structural connectivity.
In this context, it has been observed that while most patients do experience marked cognitive deficits in the immediate postoperative period, a vast majority recover at the late examination, four months after the surgery.