Matthijs Bossong

Matthijs Bossong obtained his Master’s degree in Biomedical Sciences in 2003 at Utrecht University, the Netherlands. After having worked at the Dutch institute for mental health and addiction, Matthijs started his PhD in April 2007 at the Department of Neurology and Neurosurgery of the University Medical Center Utrecht, under supervision of Prof. Nick Ramsey and Prof. René Kahn. He obtained his PhD entitled “Role of the endocannabinoid system in human brain functions relevant for psychiatric disorders” in January 2012. After his PhD, Matthijs acquired a fellowship which enabled him to work at the Institute of Psychiatry at King’s College London for three years. There he was involved in two multimodal neuroimaging projects with people who are at an ultra-high risk of developing psychosis, one of which involved treatment of at-risk individuals with cannabidiol (CBD).

Since September 2014, Matthijs has been working as postdoctoral researcher in the group of Prof. René Kahn at the Brain Center Rudolf Magnus of the UMC Utrecht, coordinating a large European multi-centre study in which the effectiveness of omega-3 fatty acids in adolescent at-risk individuals is examined. Recently, Matthijs has been awarded a Dutch fellowship for young scientists, which allows him to continue his research on the functioning of the cannabinoid system in the context of psychosis.

The endocannabinoid (eCB) system, consisting of cannabinoid receptors and accompanying ligands, has been implicated in cognitive functions which are also affected in various psychiatric disorders. In addition, behavioural evidence from healthy subjects indicates that modulation of the eCB system by administration of eCB agonists such as Δ9-tetrahydrocannabinol (THC) impairs performance on cognitive paradigms. However, the neurophysiological mechanisms underlying these effects are unknown. Here, I will present a series of functional MRI studies in which we investigated the acute effects of THC on cognitive brain function of healthy volunteers. Results of these studies show that the impact of THC administration depends on the difficulty of the task performed. Impaired performance of cognitive paradigms is demonstrated on more challenging tasks, which is associated with both activity deficits in temporal and prefrontal areas and a failure to deactivate regions of the default mode network. Normal performance levels after THC administration demonstrated for less demanding tasks are shown to be related to either increased neural effort in task-specific regions (‘neurophysiological inefficiency’) or recruitment of alternative brain areas, which suggests a change in strategy to meet cognitive demands. Together, these results provide compelling support for endocannabinoid involvement in the control of higher cognitive functions.