Optically Pumped Magnetometers to characterize neurophysiological correlates of psychiatric treatment effects

Psychiatric disorders are characterised by a clinically significant disturbance
in an individual's cognitive, affective or behavioural function and the
interaction with their environment. The mechanisms by which biological
psychiatric treatment such as electroconvulsive therapy (ECT) and psychotherapy
reduce psychiatric symptoms are only partially understood. Unravelling this
process may facilitate the development of biomarkers for psychiatric treatment
response allowing improved therapeutic efficacy. Numerous fMRI studies and
studies with a selected group of patients with deep brain stimulation shows
high potential of subcortical neurophysiological activity in understanding
psychiatric pathophysiology. However, these methods are limited in their
ability to non-invasively track (subcortical) brain activity with high
precision and in real-time. Moreover, they require patients to be motionless
positioned in an non-naturalistic testing environment, that does not allow a
patient*s cognitive, affective or behavioral function to be investigated while
interacting with the environment.
Newly developed magnetoencephalography (MEG) sensors, so-called
Optically Pumped Magnetometers (OPMs), provide an unprecedented opportunity to
overcome these issues. These sensors are smaller, lighter, and cheaper, yet
have superior sensitivity over cryogen-based MEG systems that use
Superconducting Quantum Interference Devices (SQUIDs). Importantly, they can be
placed directly on the scalp, thereby improving the sensitivity to, and
localisation accuracy of, activity in subcortical sources. Moreover, with a
wearable OPM-based array, one could record during movement, or even during
participation in (virtual reality) tasks and real-life interaction. Therefore,
OPM-MEG may enable us to understand the mechanism by which psychiatric
treatments reduce symptoms while considering interaction between the patient
and their environment.
Because MDD is one of the most common psychiatric disorders that has a
highly effective biological treatment, i.e. ECT, this disorder is of particular
interest. In patients undergoing ECT, changes in hippocampal volume are
observed, which are correlated with symptom severity and treatment-related
temporary cognitive side-effects. Yet, neuro-anatomical changes occur gradually
during ECT treatment. In contrast, pilot DBS studies demonstrated that
neurophysiological activity in various neuro-anatomical areas is almost
directly related to the depressive symptoms at the moment of measurement. Thus,
non-invasive neurophysiological MEG recordings targeting the hippocampus might
be a feasible approach to further explore the effect of ECT on depression.

The main goal is to demonstrate that OPM-MEG can be used successfully in
patients with psychiatric disorders, by allowing subjects to move whilst
recording magnetic electrophysiological activity, and has potential as a novel
diagnostic method in psychiatric care. Our primary objective is to investigate
if ECT modulates neurophysiological resting-state activity from the hippocampus
in patients with MDD. Secondarily, we investigate whether hippocampal activity
correlates with cognitive side effects and depression symptom reduction during
ECT treatment.

This is a longitudinal correlation pilot study where patients undergo OPM-MEG
recordings before and after ECT.

Specific study population: Adult patients with MDD voluntarily treated with
ECT and for whom reasonable effectivity of treatment is expected (based on
patient history or clinical judgement).
Study procedures: Patient are included for a pre- and post-treatment OPM-MEG
resting-state measurement. Study duration will be 8-10 weeks, in accordance
with duration of ECT treatment.
Risks: MEG is a safe non-invasive technique to record brain signals. The use of
OPMs has negligible risks.
Burden: Patients will have to travel to the VUmc in Amsterdam. The OPM
recording will take place in a magnetically shielded room (which is about the
size of a large freight elevator). Patients will wear a plastic cap with the
OPMs attached and will undergo resting-state recording sessions. Duration of a
data acquisition procedure will be 60 minutes.
Benefits: There is no direct benefit for the patient to be expected.