Increased cognitive workload evokes greater neurovascular coupling responses in healthy young adults

Abstract

Understanding how the brain allocates resources to match the demands of active neurons under physiological conditions is critically important. Increased metabolic demands of active brain regions are matched with hemodynamic responses known as neurovascular coupling (NVC). Several methods that allow noninvasive assessment of brain activity in humans detect NVC and early detection of NVC impairment may serve as an early marker of cognitive impairment. Therefore, non-invasive NVC assessments may serve as a valuable tool to detect early signs of cognitive impairment and dementia. Working memory tasks are routinely employed in the evaluation of cognitive task-evoked NVC responses. However, recent attempts that utilized functional near-infrared spectroscopy (fNIRS) or transcranial Doppler sonography (TCD) while using a similar working memory paradigm did not provide convincing evidence for the correlation of the hemodynamic variables measured by these two methods. In the current study, we aimed to compare fNIRS and TCD in their performance of differentiating NVC responses evoked by different levels of working memory workload during the same working memory task used as cognitive stimulation. Fourteen healthy young individuals were recruited for this study and performed an n-back cognitive test during TCD and fNIRS monitoring. During TCD monitoring, the middle cerebral artery (MCA) flow was bilaterally increased during the task associated with greater cognitive effort. fNIRS also detected significantly increased activation during a more challenging task in the left dorsolateral prefrontal cortex (DLPFC), and in addition, widespread activation of the medial prefrontal cortex (mPFC) was also revealed. Robust changes in prefrontal cortex hemodynamics may explain the profound change in MCA blood flow during the same cognitive task. Overall, our data support our hypothesis that both TCD and fNIRS methods can discriminate NVC evoked by higher demand tasks compared to baseline or lower demand tasks.

Sleep deprivation impairs cognitive performance, alters task-associated cerebral blood flow and decreases cortical neurovascular coupling-related hemodynamic responses

“…In addition, an n -back approach-based cognitive test was used to evoke NVC responses during TCD assessment and results of the n -back test were also analyzed for cognitive performance. The n -back test is designed to assess working memory, as previously described 11 , 17 . Briefly, after explanation of the assessment, participants were seated in front of a 22-inch monitor, with their dominant hand on the computer mouse.…”

“…Loss of sleep may affect several domains of cognitive functioning, however, reaction time and working memory are reported to be the most sensitive to short-term sleep deprivation 8 – 10 . Working memory is the cognitive domain that is responsible for temporarily holding information available for manipulating, processing, and is also involved in the transition of information to long-term memory 9 , 11 . Appropriate amount and quality of sleep is, therefore, essential for healthy neurocognitive function and memory consolidation, and lack of sleep is recognized to be associated with the increased risk of various neurocognitive disorders 12 .…”

Does task complexity impact the neurovascular coupling response similarly between males and females?

“…As the “ Where's Waldo? ” and 0.5‐s tasks were shown to elicit activity in brain regions in addition to the occipital regions of the cortex (Figure 4 ), future research should utilize functional near‐infrared spectroscopy (fNIRS) to assess and accurately detect specific locations of cortical activation in the superficial layers of the brain (Csipo et al, 2021 ). It is suggested that fNIRS is capable of creating a cortical map with respect to specific regions engaged in an NVC task (Phillips et al, 2016 ).…”

“…By utilizing these two measures (TCD and fNIRS) in a concurrent manner, future studies can objectively measure the deep and superficial blood supply to the cerebrum, in order to examine both the activation of the cortices and the corresponding CBV response. However, it should be noted previous TCD/fNIRS studies, while imperative, have been conducted independently rather than concurrently (Csipo et al, 2021 ). Anecdotally, a small subsample of individuals (n = 6) within the study had consistent and augmented Mayer waves present during all tasks (Figure 6 ).…”

Capillary Stalling: A Mechanism of Decreased Cerebral Blood Flow in AD/ADRD

“…Impaired neurovascular coupling is also associated with cerebral hypoperfusion. Neurovascular coupling, or functional hyperemia, is the process of an increase in neural activity leading to an increase in local CBF [ 12 ]. Functional hyperemia is necessary for normal brain function and is deficient in the elderly and AD patients [ 13 ].…”