Page 85 - JSOM Spring 2026

course compared to a control condition. The differences in findings, which align closely with the current study, suggest
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findings between this study and those of Gauthier et al. are that the prolonged driving task resulted in central fatigue
likely a result of key differences in the testing protocol, as the and novel activation patterns, thus reducing the available ox-
NVGs were comparable and the population similar between ygenation within the stimulated regions of the brain. Both
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studies. In contrast to Gauthier et al., who required participants rationales underlying the NVG-induced decrease in rScO are
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to navigate a simulated residential home while identifying ob- plausible; however, based on the worsening marksmanship
jects, the current study used a predetermined course designed to performance presently observed and the previously reported
place a cognitive load on the PFC and determine the impact of reduction in visual, navigation, and cognitive performance, it
visual input on processing. Therefore, the current study sug- is likely that NVG use stimulated neural pathways that are not
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gests that modern NVGs do not negatively impact basic work- typically activated, increasing metabolic demand to complete
ing memory and sequential processing. The conflicting results the cognitive tasks. 8,10,36
highlight the need to understand how NVG use impacts tasks
specific to warfighters, such as tactical combat casualty care, Similar to the cognitive assessment tasks, the rScO response
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vehicle operation, or artillery targeting. during marksmanship 2 was lower than the control condition.
This suggests a culmination of difficulty as marksmanship 2 and
Neuroimaging cognitive assessment tasks 1 and 2 all succeeded marksmanship
The rScO measured the cortical activation over the PFC during 1. This may indicate that strenuous tasks compound over time
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the cognitive assessment, which combined working memory and disproportionately affect the performance of subsequent
and sequential processing. The control and NVG conditions tasks, resulting in worsening performance. As described previ-
exhibited opposing changes in rScO : the control condition in- ously, these findings may result from reduced cognitive process-
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creased from Baseline, whereas the NVG condition decreased ing due to limited sensory information, 29–31 or reflect increased
from baseline for both cognitive assessment 1 and 2 (Figure 4). metabolic demand from the novelty of the task. 32–35 Coupled
As this is the first study to examine fNIRS activation during with reduced marksmanship performance, the decrease in rScO 2
NVG use, the findings were compared with relevant measures can be attributed to the multifaceted and compounding diffi-
(i.e., electroencephalogram) and tasks (working memory, se- culty of this obstacle-avoidance course, including its marksman-
quential processing). For example, the control condition aligns ship and cognitive assessment components. Further research is
with Herff et al., who reported greater cerebral oxygenation necessary to clarify these underlying mechanisms and their oc-
over the PFC throughout repeated n-back working memory currence during NVG use by investigating differences between
tasks in healthy adults under normal light conditions. The novice and experienced NVG users, and by assessing the effects
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increase in rScO reflects a fundamental increase in metabolic of NVG training interventions on cerebral activation.
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demands, which has been associated with neurovascular cou-
pling, a process where greater dilation and shunting of blood Limitations
occurs to the region in need to meet metabolic demands. This study has several limitations that should be considered
Causse et al. demonstrated that hemodynamic responses mea- before applying to military populations. Specifically, the short
sured by fNIRS are sensitive to rising cognitive load, with duration, controlled indoor setting, small sample size, and
more challenging tasks typically leading to increased cere- lack of targeting lasers, which are commonly used operation-
bral oxygenation. In addition, Causse et al. indicated that ally, may not accurately reflect all scenarios. Future research
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hemodynamic responses are often more sensitive to changes that includes these additions to the study design may yield
in cognitive performance than the outcomes of the cognitive different cognitive and neural responses. Neural imaging was
assessment. Thus, the increase in rScO during the Control limited to the PFC due to the standard NVG helmet, which
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condition likely reflects an increased metabolic demand in the restricted whole-brain assessment; future studies should target
PFC compared to the Baseline timepoint. additional regions and consider alternative helmet or fNIRS
designs. Additionally, only white phosphor NVGs were used,
In contrast to the control condition, the NVG condition ex- which may not be directly comparable to green-phosphor
hibited significantly lower rScO during cognitive assessment devices. Future research should not only examine both NVG
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tasks 1 and 2 (Figure 4). This condition-induced difference in types and longer operational periods to better assess their per-
rScO over the PFC occurred without a detectable difference formance and limitations but also consider larger populations
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in cognitive assessment performance (Figure 5). The observed with NVG experience performing tactically relevant tasks such
lower rScO over the PFC in the NVG condition compared to as applying a tourniquet or reassembling a firearm.
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the control can be explained by two differing fundamental fac-
tors, both supported by the current literature. Specifically, the Conclusion
lower rScO may reflect a reduced need for cognitive process-
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ing due to limited sensory information, similar to effects seen This study examined the impact of NVG use on gait biome-
in reduced-stimulation environments (where fewer external chanics, marksmanship, cognitive performance, and PFC ox-
stimuli decrease processing requirements). 29–31 For example, ygenation during a dynamic obstacle avoidance course. The
Chen et al. examined fNIRS and electroencephalogram (EEG) primary findings indicated that NVG use significantly impaired
responses following varying levels of auditory and visual stim- performance and increased task difficulty among NVG-naïve
ulation and found that decreases in either stimulus resulted in participants. Altered lower limb biomechanics were observed,
lower fNIRS and EEG activation. Alternatively, the unique which may increase the risk of injury and falls during NVG
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and challenging nature of the NVG task might engage neural use. Marksmanship performance decreased by 58.2% during
pathways that are not typically activated, resulting in increased NVG use, reflecting the need for enhanced training and aiming
difficulty and greater metabolic demand. 32–35 For example, Li technologies. Cognitive assessment scores were similar across
et al. reported a progressive decrease in rScO over the PFC conditions, indicating the maintenance of basic working mem-
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during a novel, complex driving task in healthy adults. These ory and sequential processing during NVG use. Notably, rScO
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