The matching of vascular supply to neuronal metabolic demand during cognitive engagement is known as neurovascular coupling (NVC). Arterial stiffness is a prominent determinant of pulsatility in the systemic circulation and may thus indirectly impact NVC. In this pilot investigation, we explored changes in carotid artery stiffness and cerebrovascular hemodynamic pulsatiltiy during cognitive engagement in healthy adults.METHODS
Twenty-seven adults (age 39±3 years, BMI 24±1kg/m2) underwent Doppler ultrasonography of the common carotid artery (CCA) combined with applanation tonometry to derive (i) CCA elastic modulus (Ep) and β-stiffness index; (ii) CCA flow pulsatility index (PI); (iii) CCA pulse pressure, (iv) CCA augmentation index (AIx). Cerebral PI was assessed using transcranial Doppler at the middle cerebral artery (MCA). All measures were made at rest and during an incongruent Stroop task.RESULTS
CCA PI was reduced (1.75±0.06 to 1.57±0.06, P < 0.05) while MCA PI was unchanged (0.75±0.02 to 0.75±0.02, P > 0.05) during Stroop. Brachial pulse pressure increased during Stroop (43±1 to 46±1mm Hg, P < 0.05) while CCA pulse pressure was unchanged (36±1 to 35±1mm Hg, P > 0.05). Similarly, CCA Ep (54.5±5.5 to 53.8 ± 4.9 kPa, P > 0.05) and β-stiffness index (4.4±0.4 to 4.2±0.3 aU, P > 0.05) were unchanged. CCA AIx increased (1±4 to 13±4%, P < 0.05).CONCLUSION
Carotid pressure pulsatility is unaltered while carotid flow pulsatility is reduced during cognitive engagement. Carotid artery stiffness does not change suggesting that factors other than the dynamic elastic properties of the CCA buffer cerebrovascular hemodynamic pulsatility during cognitive engagement.