Background: Alzheimer’s disease’s (AD) prevalence is projected to increase as the population ages and current treatments are minimally effective. Transcranial photobiomodulation (t-PBM) with near-infrared (NIR) light penetrates into the cerebral cortex, stimulates the mitochondrial respiratory chain, and increases cerebral blood flow. Preliminary data suggests t-PBM may be efficacious in improving cognition in people with early AD and amnestic mild cognitive impairment (aMCI). Methods: In this randomized, double-blind, placebo-controlled study with aMCI and early AD participants, we will test the efficacy, safety, and impact on cognition of 24 sessions of t-PBM delivered over 8 weeks. Brain mechanisms of t-PBM in this population will be explored by testing whether the baseline tau burden (measured with ¹⁸F-MK6240), or changes in mitochondrial function over 8 weeks (assessed with ³¹P-MRSI), moderates the changes observed in cognitive functions after t-PBM therapy. We will also use changes in the fMRI Blood-Oxygenation-Level-Dependent (BOLD) signal after a single treatment to demonstrate t-PBM-dependent increases in prefrontal cortex blood flow. Conclusion: This study will test whether t-PBM, a low-cost, accessible, and user-friendly intervention, has the potential to improve cognition and function in an aMCI and early AD population.

Traumatic brain injury (TBI) is a common cause of neurologic morbidity for which few effective therapies exist, especially during the chronic stage. A potential therapy for chronic TBI is transcranial photobiomodulation (tPBM). tPBM is a noninvasive neuromodulation technique that uses light to stimulate the cortex and increase blood flow and metabolism while also enhancing cognition and improving affect. There has been much work focusing on the efficacy of tPBM in acute TBI in small animals, but much less work has focused on chronic TBI. Patients with chronic TBI manifest microvascular injury, which may serve as a modifiable treatment target for tPBM. There is a need to study and improve tPBM, as the currently implemented protocols targeting microvascular injury have been relatively unsuccessful. This review includes 16 studies, which concluded that after tPBM application, there were improvements in neuropsychological outcomes in addition to increases in cerebral blood flow. However, these conclusions are confounded by differing tPBM parameters, small sample sizes, and heterogenous TBI populations. While these results are encouraging, there is a need to further understand the therapeutic potential of tPBM in chronic TBI.

The decisional reference point, the central mechanism underlying behavioral economics, conditions our evaluations of all reinforcers. Whether a given event is experienced as positive or negative depends on this reference point. A pathological elevation of the reference point would lead a person to experience once pleasurable activities as negative reinforcers. Thus, it has been hypothesized that a reference point pathology may play a critical role in the symptomology of major depressive disorder (MDD). Here, we test the hypothesis that the reference point is pathologically elevated and dynamically inflexible in patients suffering with MDD compared to healthy controls. We find that depression is associated with a significant elevation of the reference point, and the magnitude of this elevation correlates with disease severity. The ability of patients with MDD to dynamically adjust their reference point to the environment is also dysfunctional. Our findings link the previously demonstrated treatment of depression by deep brain stimulation to modulation of the reference point in the anterior cingulate cortex and identify pathology in the dynamics of reference point setting as a potential cognitive mechanism in the disorder. Finally, these results reveal that a three-minute video game-like task measuring the reference point strongly correlates with depression severity. After further testing for clinical validity, this rapid assay may serve as a potential tool for assessing and monitoring depression.

Alzheimer’s disease (AD) is the most common type of dementia worldwide, accounting for 60–70% of cases (World Health Organization, 2025). Although treatments for AD have emerged (for a review, see ...