The Psychomotor Vigilance Test (PVT) is considered the gold standard for objectively assessing behavioral alertness and sustained attention. Because it is a simple reaction-time task, it is uniquely resistant to practice effects, making it a highly reliable tool for tracking cognitive recovery and stability over long periods. During the test, participants must respond as quickly as possible to visual or auditory stimuli that appear at unpredictable intervals. The primary outcomes are response speed (often measured as reciprocal reaction time, or $1/RT$), attentional lapses (delayed responses exceeding 500 ms), and false starts.

In the study of traumatic brain injury (TBI), the PVT is valued for its extreme sensitivity to "attentional instability"—the fluctuating and unpredictable ability to maintain a state of readiness. Individuals with TBI frequently exhibit slower response speeds, significantly higher performance variability, and frequent lapses compared to healthy controls. Neuroimaging shows that these performance drops are tied to altered cerebral blood flow in frontal and thalamic networks. This suggests a compensatory neural cost, where the injured brain must work harder and recruit extra resources to achieve the same level of focus that a healthy brain maintains effortlessly. While the standard test lasts 10 minutes to capture "fatigability" (decline over time), a brief 3-minute version (PVT-B) is often utilized for rapid screening in busy clinical or operational environments.

Analogy for Attentional Instability:Performing a sustained attention task with a brain injury is like trying to listen to a weak radio signal during a storm. While the music may come through clearly for a few moments (the fast responses), unpredictable static (the lapses) constantly interrupts the broadcast. To keep the signal clear, the listener must constantly get up and adjust the antenna (compensatory effort), a process that is mentally draining and eventually leads the listener to give up entirely as the storm worsens (fatigability).

This episode discusses sources provide an overview and structured literature review concerning the complex relationship between trauma-induced hypervigilance and performance on the BrainSherpa.app Psychomotor Vigilance Task (PVT). The first source introduces hypervigilance as a state of heightened alertness often linked to past trauma, explaining its impact on cognitive functions like sustained attention, and noting that it generally impairs PVT performance, leading to increased lapses and slower response times. The second, more formal review synthesizes evidence, concluding that while hypervigilance causes trauma survivors to exhibit increased threat monitoring and scanning, this does not translate to improved PVT results; instead, individuals with chronic hypervigilance often experience greater fatigue and impaired sustained attention due to high cognitive and physiological costs. Both texts emphasize that understanding this interplay is vital for developing effective therapeutic interventions for trauma survivors, such as Cognitive Behavioral Therapy (CBT).

This episode is from a research article titled "Illuminating Cognitive Performance: Assessing the Role of Transcranial Photobiomodulation in Augmenting Cognition," published in MILITARY MEDICINE in 2025. This study investigates the use of transcranial photobiomodulation (tPBM), a noninvasive technique utilizing near-infrared light, to potentially improve cognitive performance. Using a small sample of eight predominantly female participants, the researchers compared a tPBM group to a sham group across various cognitive assessments and psychological measures. Key findings include statistically significant improvements in processing speed (Reaction Time) and plasticity for the tPBM group on the Brain Gauge test, as well as enhanced working memory on high-load orientation tasks. Furthermore, the tPBM group demonstrated greater consistency and a significant increase in pupil dilation from session one to session two, suggesting an effect on sustained attention and the underlying neural systems. The authors conclude that tPBM shows promise for enhancing cognitive function, especially under high cognitive demand, and recommend further research with larger samples, particularly for military and clinical applications.

https://doi.org/10.1093/milmed/usaf227