Spotlight on Pierre Marquet

New Chair at Laval working to prevent psychiatric disorders

At first glance, the link between photonics and psychiatry might not seem obvious. But, Pierre Marquet knows bringing these two disciplines together could help prevent psychiatric disorders in at-risk children.

“It is true there is a big gap between the disciplines,” says Marquet. “In fact, the challenge is not so much to combine them, but to develop new, cutting-edge technologies dedicated to a brand new field: neurophotonics.”

Marquet is the Canada Excellence Research Chair in Neurophotonics at the Université Laval. He comes to Quebec City from Switzerland, where he was director of a psychiatric neurosciences research unit at the University Hospital of Lausanne, as well as in charge of the hospital’s specialized section for treating mood and personality disorders.

He stresses that treatments currently available for major psychiatric disorders such as schizophrenia, bipolar disorders and major depression are “largely insufficient.” He believes one barrier to significant advancements in treatment is the lack of proper tools to identify biomarkers. This identification would help guide early diagnosis, and ensure that at-risk children are monitored.

 Psychiatric disorders are illnesses for which we have practically no reliable biomarkers right now. 

“I believe that, if we could detect a serious psychiatric disorder earlier, it is a good bet we would be able to improve the disease’s evolution for the sufferer,” he says.

While spectacular advances in neuroimaging (such as MRIs and PET scans) have given us a glimpse at relationships between our psyche and brain, the discrete brain changes that accompany changes in a person’s mental state are still hard to detect. Marquet, however, believes that “multimodal approaches,” combining existing brain-imaging tools with new—particularly, optical—techniques, could help drastically improve detection of these discrete brain changes. That would lead to earlier diagnosis—perhaps even before any disabling clinical symptoms appear. Such tools would also help doctors follow a disease’s progression in a patient.

“Advanced photonics or optics techniques can be of great help,” says Marquet. “We can, in combination with an MRI, use noninvasive techniques, such as near infrared spectroscopy, to study in detail the complex structural and functional organization of our brain [and] help identify and understand the complex neurobiological processes, in their early stages, that will slowly and significantly alter brain function and lead to the appearance of psychiatric disorders.”

Marquet is working to identify what he calls “new vulnerability biomarkers” (or indicators) of future psychiatric disease—especially in children from families where one or both parents suffer from a psychiatric disorder, since they are more at risk of developing a mental disorder later in life, as young adults.

“Psychiatric disorders are illnesses for which we have practically no reliable biomarkers right now,” says Marquet. “In contrast, for somatic illnesses like cancer or diabetes, you can often detect the illness early and follow its evolution, thanks, specifically, to biomarkers. The earlier we detect it, the better the chance there is of treating the disease—or, at least, of drastically improving its prognosis.”

The idea that major psychiatric disorders have biological determinants that are present in childhood has only recently gained acceptance. Marquet believes studying the dynamics of neuronal cells from patients and their children will make it possible to identify new cellular biomarkers of vulnerability for psychiatric illnesses.

Marquet will take samples through skin biopsies and children’s hair samples.

“Practically speaking, we can reprogram the harvested cells drawn from defined lineages,” he says, “and so obtain living neurons and astrocytes [the two main types of brain cells] with the necessary genetic makeup to let us observe certain characteristics—or phenotypes—of the disease.”

“This allows you to consider the hypothesis that some phenotypes are already found in vitro in the neuronal network, or at the neuron level itself,” says Marquet.

Incredibly, Marquet can do this analysis in a petri dish, using “digital holographic microscopy” (DHM). Marquet developed this noninvasive technique to explore the structure and dynamics of neuronal networks at the nanometric scale.

“If you use DHM to compare the neuronal network dynamics of patients and their offspring to a control group, you can extremely accurately explore the different phenotypes related to neuronal dynamics, as well as their underlying mechanisms,” he says. “You can also mimic stressful environments, and evaluate how the neuronal network reorganizes itself and adapts. From this, we can address, at a cellular level, the question of vulnerability or resilience to stress. And stress is a significant factor in the aggravation or relapse of a psychiatric illness.”

Marquet explains he will not be medicating identified offspring with classical psychotropic drugs.

“We are absolutely not going to give antipsychotic drugs to children,” he says. “Other than the fact that this practice could lead to their stigmatization, it also raises many ethical issues.”

“Our first task is to detect young children at risk by identifying a set of biomarkers of vulnerability that identify a trajectory of risk. We will then try to normalize some of the biomarkers of vulnerability in order to curb the trajectory of risk—particularly, using psychological or psychotherapeutic interventions that will also help these children cope with their everyday problems,” he says.

“Ideally, these interventions would help prevent the development of the psychiatric illness in its most disabling forms,” says Marquet. “Ultimately, considering the amazing plasticity of the brain during childhood, there is even hope that advances in this research will help lead to early interventions meant to cure.”