Measuring acute effects of subanesthetic ketamine on cerebrovascular hemodynamics in humans using TD-fNIRS.

Quantifying neural activity in natural conditions (i.e. conditions comparable to the standard clinical patient experience) during the administration of psychedelics may further our scientific understanding of the effects and mechanisms of action. This data may facilitate the discovery of novel biomarkers enabling more personalized treatments and improved patient outcomes. In this single-blind, placebo-controlled study with a non-randomized design, we use time-domain functional near-infrared spectroscopy (TD-fNIRS) to measure acute brain dynamics after intramuscular subanesthetic ketamine (0.75 mg/kg) and placebo (saline) administration in healthy participants (n = 15, 8 females, 7 males, age 32.4 ± 7.5 years) in a clinical setting. We found that the ketamine administration caused an altered state of consciousness and changes in systemic physiology (e.g. increase in pulse rate and electrodermal activity). Furthermore, ketamine led to a brain-wide reduction in the fractional amplitude of low frequency fluctuations, and a decrease in the global brain connectivity of the prefrontal region. Lastly, we provide preliminary evidence that a combination of neural and physiological metrics may serve as predictors of subjective mystical experiences and reductions in depressive symptomatology. Overall, our study demonstrated the successful application of fNIRS neuroimaging to study the physiological effects of the psychoactive substance ketamine in humans, and can be regarded as an important step toward larger scale clinical fNIRS studies that can quantify the impact of psychedelics on the brain in standard clinical settings.

Patient motivation for participating in clinical trials for depression: validation of the motivation for clinical trials inventory-depression.

The motivation for clinical trials inventory-depression (MCTI-D) was developed and evaluated for assessing motivations to participate in clinical trials on depression. Sixty-four participants completed the MCTI-D: 40 individuals expressing interest in participating in a randomized clinical trial (RCT); and 24 clinic patients receiving traditional care for depression. Content validity was supported by feedback derived from a panel of experts in depression research and respondents completing the measure. The motivation most frequently endorsed for participating in an RCT was the desire to help others and/or to further science. The potential stigma associated with seeing a psychiatrist was reported to have the least influence. Patients expressed a greater likelihood to participate in RCTs that involved psychotherapy than in experimental medication or placebo-controlled trials. Data from the MCTI-D may provide useful information for depression researchers to consider as possible influences on patients' decisions about whether or not they will participate.