Continuous wavelet transform of laser-Doppler signals from facial microcirculation reveals vasomotion asymmetry

Deep and surface hemodynamic signal from functional time resolved transcranial near infrared spectroscopy compared to skin flowmotion

“…Subsequently, the preliminary test on the information carried by the two LDF signals collected on the two temples showed that vasomotion related dynamics detected by the two probes were highly correlated and comparable. Given that it would be virtually impossible to thoroughly map the entire forehead by an empiric approach aimed at finding potential discrepancies in local vasomotor responses [24], these results basically revealed the affinity in the information conveyed by the two LDF recordings, thus suggesting that typical vasomotor and autoregulation dynamics in the two measurement sites could be considered homogeneous. This preliminary experiment also showed the effects of the strong hemodynamic perturbation induced by VM: (a) a sharp synchronization of central and peripheral oscillations during the forced expiration, indicated by the high value of correlation between the two LDF channels; and (b) a marked desynchronization following VM, during recovery.…”

“…The rationale of the preliminary experiment was to validate that two LDF measurements, apart from the site where the fNIRS probe is placed, are sufficiently correlated to be assumed as acceptable surrogates of a LDF measurement in the same location of the fNIRS measure, which was not possible due to optic crosstalk between the two devices, and to the disturbance on fNIRS measurements by LDF. The homogeneity of LDF measurements in different sites of human face was to be tested because human face is an heterogeneous microvascular region: angiographic characteristics of deep horizontal sub-dermal plexus, endothelial and vascular smooth muscle cell heterogeneity, and plasticity of the microvasculature, autonomic asymmetry and facial neuropsychological asymmetry are possible causes of microvascular asymmetry [24].…”

Facial thermal and blood perfusion patterns of human emotions: Proof-of-Concept

“…In the face, there is an increase in the diameter of the pupils to increase the visual field, the muscles contract, and vasoconstriction occurs, which generates an increase in resistance and a reduction in the blood flow [40]. A study by Mitja Benedičič et al [57] reported asymmetry in the face's average blood flow and statistically significant differences in the spectral amplitude of the vasomotion (defined as spontaneous lowfrequency oscillatory constrictions of the microvascular smooth muscle), which depend on intrinsic cardiac, respiratory, and myogenic activities and neural and endothelial mechanisms. The authors reported a higher degree of vasomotion activity on the right side of the forehead and a greater level of blood flow and vasomotion in the cheeks than on the forehead [57].…”

The presence of synchronized perfusion dips in the microcirculation of the resting nail bed

“…Microcirculatory differences were also noted between the digits of left and right hand in the present study. Previous work has shown that there are microcirculatory differences in other parts of the body as well, such as the microcirculation of the face, when vasomotion has been studied using LDF [35]. This raises a few questions, particularly since the presence of perfusion dips seem to be centrally mediated while there also is a local difference between anatomical sites.…”