The effect of adrenergic blockade on blushing and facial flushing

Red Backgrounds Enhance Dominance in Human Faces and Shapes

Red color signals dominance in both animals and humans. This study investigated whether a red background color influences the perception of dominance in human faces and geometric shapes. The facial stimuli consisted of computer-generated faces, quantitatively morphed into nine levels of dominance, ranging from less dominant to more dominant. This included East-Asian female faces in Experiment 1 and male faces in Experiment 2. The face stimuli were presented against three background colors: red, green, and gray. Participants were instructed to categorize the faces as either obedient or dominant by pressing the corresponding labeled keys. The results showed that faces were more likely to be perceived as dominant when presented against a red background than against green or gray backgrounds, for both female and male faces. Additionally, two questionnaire surveys showed that the perception of dominance also increased for shapes presented against a red background. However the effect of red diminished in the absence of the actual perception of the color red. These results suggest that the perception of dominance in both human faces and objects is enhanced by the presence of red, possibly due to evolutionary factors related to the perception of red.

Neural cell-types and circuits linking thermoregulation and social behavior

Understanding how social and affective behavioral states are controlled by neural circuits is a fundamental challenge in neurobiology. Despite increasing understanding of central circuits governing prosocial and agonistic interactions, how bodily autonomic processes regulate these behaviors is less resolved. Thermoregulation is vital for maintaining homeostasis, but also associated with cognitive, physical, affective, and behavioral states. Here, we posit that adjusting body temperature may be integral to the appropriate expression of social behavior and argue that understanding neural links between behavior and thermoregulation is timely. First, changes in behavioral states-including social interaction-often accompany changes in body temperature. Second, recent work has uncovered neural populations controlling both thermoregulatory and social behavioral pathways. We identify additional neural populations that, in separate studies, control social behavior and thermoregulation, and highlight their relevance to human and animal studies. Third, dysregulation of body temperature is linked to human neuropsychiatric disorders. Although body temperature is a "hidden state" in many neurobiological studies, it likely plays an underappreciated role in regulating social and affective states.

Characterization of forehead blood flow bias on NIRS signals during neural activation with a verbal fluency task

The major problem of near-infrared spectroscopy (NIRS) for brain activity measurement during verbal fluency task is the overlapping forehead scalp blood flow (FBF) on the target cerebral blood flow (CBF). There could be among-individual differences in the influence of FBF on CBF. We investigated effects of FBF on CBF by comparing signals obtained through a laser Doppler flowmeter (LDF) and NIRS using the modified Beer-Lambert Law (MBLL). Among 25 healthy individuals, 7 participants showed a strong correlation between LDF and NIRS signals (r_s >0.500). There were no significant differences according to age or sex. Subsequently, we applied the hemodynamic separation method to the values calculated using the MBLL (Δ[oxy-Hb]_M): to separate the concentration of oxygenated hemoglobin in the forehead (Δ[oxy-Hb]_F) and cerebral cortex (Δ[oxy-Hb]_C). First, we found that the influence of Δ[oxy-Hb]_F on Δ[oxy-Hb]_C in the high r_s group was almost twice as large as that in the low r_s group. Second, presence of sex and age differences in the influence of Δ[oxy-Hb]_F on Δ[oxy-Hb]_C were suggested. Based on the results, we discuss the factors affecting FBF and the resulting variations in NIRS signals.

Does facial redness really affect emotion perception? Evidence for limited generalisability of effects of facial redness on emotion perception in a large sample

We conducted a preregistered study (N = 609) to conceptually replicate and extend prior research regarding the effects of facial redness on emotion perception. In a within-subjects design, participants saw emotion faces (anger, happiness, fear, neutral) of a random female and a random male target with default facial colouration and increased facial redness and were asked to simultaneously rate the intensity of six emotions (happiness, surprise, sadness, fear, disgust, anger) for each emotion face. The emotion intensity was rated higher, when the emotion face and the rated emotion matched than when the emotion face and the rated emotion did not match. However, increased facial redness did not influence the intensity of the rated emotion. The results of this conceptual replication limit the generalisability of previous findings, challenge the assumption that facial redness is used as a cue to infer emotions, and point to the necessity to develop a more nuanced theoretical account of contextual boundaries.

Cortical hemodynamic mapping of subthalamic nucleus deep brain stimulation in Parkinsonian patients, using high-density functional near-infrared spectroscopy

Subthalamic nucleus deep brain stimulation (STN-DBS) is an effective treatment for idiopathic Parkinson's disease. Despite recent progress, the mechanisms responsible for the technique's effectiveness have yet to be fully elucidated. The purpose of the present study was to gain new insights into the interactions between STN-DBS and cortical network activity. We therefore combined high-resolution functional near-infrared spectroscopy with low-resolution electroencephalography in seven Parkinsonian patients on STN-DBS, and measured cortical haemodynamic changes at rest and during hand movement in the presence and absence of stimulation (the ON-stim and OFF-stim conditions, respectively) in the off-drug condition. The relative changes in oxyhaemoglobin [HbO], deoxyhaemoglobin [HbR], and total haemoglobin [HbT] levels were analyzed continuously. At rest, the [HbO], [HbR], and [HbT] over the bilateral sensorimotor (SM), premotor (PM) and dorsolateral prefrontal (DLPF) cortices decreased steadily throughout the duration of stimulation, relative to the OFF-stim condition. During hand movement in the OFF-stim condition, [HbO] increased and [HbR] decreased concomitantly over the contralateral SM cortex (as a result of neurovascular coupling), and [HbO], [HbR], and [HbT] increased concomitantly in the dorsolateral prefrontal cortex (DLPFC)-suggesting an increase in blood volume in this brain area. During hand movement with STN-DBS, the increase in [HbO] was over the contralateral SM and PM cortices was significantly lower than in the OFF-stim condition, as was the decrease in [HbO] and [HbT] in the DLPFC. Our results indicate that STN-DBS is associated with a reduction in blood volume over the SM, PM and DLPF cortices, regardless of whether or not the patient is performing a task. This particular effect on cortical networks might explain not only STN-DBS's clinical effectiveness but also some of the associated adverse effects.

Treatment Options for Fear of Blushing

PURPOSE OF REVIEW

To review mechanisms of blushing and fear of blushing from physiological, neuropharmacological and psychological viewpoints, and to evaluate current forms of treatment for blushing-related fear.

RECENT FINDINGS

Blushing appears to be driven primarily by sympathetic adrenomedullary and neural vasodilator discharge, possibly in association with secondary neurovascular inflammation. Psychological risk factors for fear of blushing include social anxiety, coupled with heightened self-focused attention and inflated beliefs about the likelihood and social costs of blushing. In addition, schemas of emotional inhibition, social isolation and alienation may underlie blushing-related fears. Established psychological treatments for fear of blushing include task concentration training, exposure, cognitive therapy, social skills training, psychoeducation and applied relaxation. More novel approaches include mindfulness and mindful self-compassion, video feedback and imagery rescripting. There are no established pharmacological treatments specifically for fear of blushing. However, selective serotonin reuptake inhibitors and serotonin-norepinephrine reuptake inhibitors are effective treatments for social anxiety disorder and may thus help some patients manage their fear of blushing. A reactive sympathetic nervous system may interact with psychological predispositions to intensify fear of blushing. These physiological and psychological risk factors could be promising targets for treatment.

Does α1-adrenergic receptor blockade modulate sweating during incremental exercise in young endurance-trained men?

PURPOSE

Human eccrine sweat glands respond to α₁-adrenergic receptor agonists. We recently reported that adrenergic mechanisms contribute to sweating in endurance-trained men during an incremental exercise to volitional fatigue. However, it remains unclear if this response is mediated by α₁-adrenergic receptor activation.

METHODS

Twelve endurance-trained men performed an incremental cycling bout until exhaustion while wearing a water-perfused suit to clamp skin temperature at ~ 34 °C. Bilateral forearm sweat rates were measured wherein the distal area was treated with either 1% terazosin (α₁-adrenergic receptor antagonist) or saline solution on the opposite limb (Control) via transdermal iontophoresis. We also measured proximal bilateral forearm sweat rate in untreated sites to confirm that no between-limb differences in forearm sweat rate occurred. Once sweat rate returned to pre-exercise resting levels at ~ 20 min postexercise, 0.25% phenylephrine (α₁-adrenergic receptor agonist) was iontophoretically administered to skin to verify α₁-adrenergic receptor blockade.

RESULTS

Sweat rates at the proximal untreated right and left forearm sites were similar during exercise (interaction, P = 0.581). Similarly, no effect of terazosin on sweat rate was measured relative to control site (interaction, P = 0.848). Postexercise administration of phenylephrine increased sweat rate at the control site (0.08 ± 0.09 mg cm^-2 min^-1), which was suppressed by ~ 90% at the terazosin-treated site (0.01 ± 0.02 mg cm^-2 min^-1) (P = 0.026), confirming that α₁-adrenergic receptor blockade was intact.

CONCLUSION

Our findings demonstrate that α₁-adrenergic receptors located at eccrine sweat glands do not contribute to eccrine sweating during incremental exercise in young endurance-trained men.

Vascular response to social cognitive performance measured by infrared thermography: A translational study from mouse to man

To assess complex social recognition in mice, we previously developed the SocioBox paradigm. Unexpectedly, 4 weeks after performing in the SocioBox, mice displayed robust social avoidance during Y-maze sociability testing. This unique "sociophobia" acquisition could be documented in independent cohorts. We therefore employed infrared thermography as a non-invasive method of stress-monitoring during SocioBox testing (presentation of five other mice) versus empty box. A higher Centralization Index (body/tail temperature) in the SocioBox correlated negatively with social recognition memory and, after 4 weeks, with social preference in the Y-maze. Assuming that social stimuli might be associated with characteristic thermo-responses, we exposed healthy men (N = 103) with a comparably high intelligence level to a standardized test session including two cognitive tests with or without social component (face versus pattern recognition). In some analogy to the Centralization Index (within-subject measure) used in mice, the Reference Index (ratio nose/malar cheek temperature) was introduced to determine the autonomic facial response/flushing during social recognition testing. Whereas cognitive performance and salivary cortisol were comparable across human subjects and tests, the Face Recognition Test was associated with a characteristic Reference Index profile. Infrared thermography may have potential for discriminating disturbed social behaviors.

Loratadine augments emotional blushing

The aim of this study was to determine whether loratadine, a selective inverse agonist of peripheral histamine H₁ receptors, would reduce emotional blushing. Loratadine (10 mg) or placebo was administered orally one hour before 31 healthy participants sang a children's nursery rhyme to evoke embarrassment and blushing. Skin blood flow was monitored via a laser Doppler probe attached to the cheek. Increases in facial blood flow while participants sang were greater in the loratadine than the placebo group (mean increase ± standard deviation 71 ± 52% in the loratadine group versus 35 ± 37%, p = .036). However, perceptions of blushing were similar in both groups. These findings suggest that loratadine augmented blushing rather than inhibiting it. Thus, histamine released during blushing may inhibit acute increases in facial blood flow by evoking H₁ receptor-mediated vasoconstriction.

Effects of Face and Background Color on Facial Expression Perception

Detecting others' emotional states from their faces is an essential component of successful social interaction. However, the ability to perceive emotional expressions is reported to be modulated by a number of factors. We have previously found that facial color modulates the judgment of facial expression, while another study has shown that background color plays a modulatory role. Therefore, in this study, we directly compared the effects of face and background color on facial expression judgment within a single experiment. Fear-to-anger morphed faces were presented in face and background color conditions. Our results showed that judgments of facial expressions was influenced by both face and background color. However, facial color effects were significantly greater than background color effects, although the color saturation of faces was lower compared to background colors. These results suggest that facial color is intimately related to the judgment of facial expression, over and above the influence of simple color.

Seeing a Blush on the Visible and Invisible Spectrum: A Functional Thermal Infrared Imaging Study

So far blushing has been examined in the context of a negative rather than a positive reinforcement where visual displays of a blush were based on subjective measures. The current study used infrared imaging to measure thermal patterns of the face while with the use of a video camera quantified on the visible spectrum alterations in skin color related to a compliment. To elicit a blush a three-phase dialog was adopted ending or starting with a compliment on a female sample (N = 22). When the dialog ended with a compliment results showed a linear increase in temperature for the cheek, and forehead whereas for the peri-orbital region a linear decrease was observed. The compliment phase marked the highest temperature on the chin independent of whether or not the experiment started with a compliment contrary to other facial regions, which did not show a significant change when the experiment started with a compliment. Analyses on the visible spectrum showed that skin pigmentation was getting deep red in the compliment condition compared to the serious and social dialog conditions for both the forehead and the cheeks. No significant association was observed between temperature values and erythrocyte displays on the forehead and cheek. Heat is the physiological product of an arousing social scenario, however, preconceived notions about blushing propensity seem to drive erythrocyte displays and not necessarily conscious awareness of somatic sensations.

Modelling confounding effects from extracerebral contamination and systemic factors on functional near-infrared spectroscopy

Haemodynamics-based neuroimaging is widely used to study brain function. Regional blood flow changes characteristic of neurovascular coupling provide an important marker of neuronal activation. However, changes in systemic physiological parameters such as blood pressure and concentration of CO2 can also affect regional blood flow and may confound haemodynamics-based neuroimaging. Measurements with functional near-infrared spectroscopy (fNIRS) may additionally be confounded by blood flow and oxygenation changes in extracerebral tissue layers. Here we investigate these confounds using an extended version of an existing computational model of cerebral physiology, ‘BrainSignals’. Our results show that confounding from systemic physiological factors is able to produce misleading haemodynamic responses in both positive and negative directions. By applying the model to data from previous fNIRS studies, we demonstrate that such potentially deceptive responses can indeed occur in at least some experimental scenarios. It is therefore important to record the major potential confounders in the course of fNIRS experiments. Our model may then allow the observed behaviour to be attributed among the potential causes and hence reduce identification errors.

•

Confounding of fNIRS haemoglobin signals is simulated using a computational model.

•

Model is extended to simulate scalp haemodynamics.

•

Changes in blood pressure and CO₂ can mimic and mask functional activation.

•

Experimental recording of systemic factors is recommended to aid interpretation.

Hemodynamic signals in fNIRS

Near-infrared spectroscopy (NIRS) was originally designed for clinical monitoring of tissue oxygenation, and it has also been developed into a useful tool in neuroimaging studies, with the so-called functional NIRS (fNIRS). With NIRS, cerebral activation is detected by measuring the cerebral hemoglobin (Hb), where however, the precise correlation between NIRS signal and neural activity remains to be fully understood. This can in part be attributed to the situation that NIRS signals are inherently subject to contamination by signals arising from extracerebral tissue. In recent years, several approaches have been investigated to distinguish between NIRS signals originating in cerebral tissue and signals originating in extracerebral tissue. Selective measurements of cerebral Hb will enable a further evolution of fNIRS. This chapter is divided into six sections: first a summary of the basic theory of NIRS, NIRS signals arising in the activated areas, correlations between NIRS signals and fMRI signals, correlations between NIRS signals and neural activities, and the influence of a variety of extracerebral tissue on NIRS signals and approaches to this issue are reviewed. Finally, future prospects of fNIRS are described.

Differences in the Pulsatile Component of the Skin Hemodynamic Response to Verbal Fluency Tasks in the Forehead and the Fingertip

Several studies have claimed that hemodynamic signals measured by near-infrared spectroscopy (NIRS) on the forehead exhibit different patterns during a verbal fluency task (VFT) in various psychiatric disorders, whereas many studies have noted that NIRS signals can reflect task-related changes in skin blood flow. If such a task-related skin hemodynamic response is also observed in the fingertip, a simpler biomarker may be developed. Furthermore, determining the difference in the response pattern may provide physiological insights into the condition. We found that the magnitude of the pulsatile component in skin hemodynamic signals increased on the forehead (p < 0.001 for N = 50, p = 0.073 for N = 8) but decreased on the fingertip (p < 0.001, N = 8) during the VFT, whereas the rate in both areas increased (p < 0.02, N = 8). We also did not find a repetition effect in both the rate and the magnitude on the fingertip, whereas the effect was present in the magnitude (p < 0.02, N = 8) but not in the rate on the forehead. These results suggest that the skin vasomotor system in the forehead could have a different vessel mechanism to psychological tasks compared to the fingertip.

Intrapersonal and interpersonal concomitants of facial blushing during everyday social encounters

Facial blushing may usually be undesirable but may have an ameliorative function for some individuals under some circumstances. Researchers have studied the blush in laboratory settings, but not in daily life. In the present research, conducted with young adults, we employed for the first time an event-contingent recording method for assessing facial blushing during every-day social encounters. Blushing was associated with feeling embarrassed, ashamed, and exposed. These findings, though based on correlational analyses, are consistent with the idea that blushing is often unpleasant and can be maladaptive, and may contribute to the common belief that blushing is an undesirable response. Frequent blushers generally reported lower levels of dominant behavior, higher levels of submissive behavior, and perceived their social interaction partners as more powerful and less affiliative. This was independent of whether they blushed or not, suggesting that altered social behaviors and perceptions are associated with blushing-associated traits rather than with the blushing state. The experience of the blush varied as a function of the frequency with which a person blushed. Blushing was associated with higher levels of shame in frequent blushers than in infrequent blushers. In infrequent blushers, blushing was associated with higher levels of pleasant affect, suggesting that for infrequent blushers the blush may occur in positive social encounters.

Identifying and quantifying main components of physiological noise in functional near infrared spectroscopy on the prefrontal cortex

Functional Near-Infrared Spectroscopy (fNIRS) is a promising method to study functional organization of the prefrontal cortex. However, in order to realize the high potential of fNIRS, effective discrimination between physiological noise originating from forehead skin haemodynamic and cerebral signals is required. Main sources of physiological noise are global and local blood flow regulation processes on multiple time scales. The goal of the present study was to identify the main physiological noise contributions in fNIRS forehead signals and to develop a method for physiological de-noising of fNIRS data. To achieve this goal we combined concurrent time-domain fNIRS and peripheral physiology recordings with wavelet coherence analysis (WCA). Depth selectivity was achieved by analyzing moments of photon time-of-flight distributions provided by time-domain fNIRS. Simultaneously, mean arterial blood pressure (MAP), heart rate (HR), and skin blood flow (SBF) on the forehead were recorded. WCA was employed to quantify the impact of physiological processes on fNIRS signals separately for different time scales. We identified three main processes contributing to physiological noise in fNIRS signals on the forehead. The first process with the period of about 3 s is induced by respiration. The second process is highly correlated with time lagged MAP and HR fluctuations with a period of about 10 s often referred as Mayer waves. The third process is local regulation of the facial SBF time locked to the task-evoked fNIRS signals. All processes affect oxygenated haemoglobin concentration more strongly than that of deoxygenated haemoglobin. Based on these results we developed a set of physiological regressors, which were used for physiological de-noising of fNIRS signals. Our results demonstrate that proposed de-noising method can significantly improve the sensitivity of fNIRS to cerebral signals.

Topical ibuprofen inhibits blushing during embarrassment and facial flushing during aerobic exercise in people with a fear of blushing

The flush that develops during whole-body heat stress depends partly on prostaglandins production in the skin. Variations in the strength of this local mechanism may contribute to individual differences in susceptibility to blushing and associated anxiety. To investigate this in the present study, the anti-inflammatory agent ibuprofen (which blocks prostaglandins formation) was applied topically to a small area of the cheek in 16 participants with a fear of blushing and in another 14 without this fear. Changes in skin blood flow were monitored at the ibuprofen-treated site and at a mirror image control site while participants sang (to induce embarrassment and blushing) and during aerobic exercise (to induce flushing). The topical ibuprofen treatment inhibited increases in cheek blood flow in both groups during both of these tasks. However, increases in cheek blood flow were greater in participants with high than low fear of blushing immediately after exercise. These findings suggest that prostaglandins contribute to dilatation of facial blood vessels both during emotional arousal (embarrassment) and aerobic exercise. Furthermore, fear of blushing may be associated with mechanisms that delay the resumption of normal vascular tone after a period of vasodilatation. Whether topical ibuprofen gel is suitable for intermittent or long-term use as an aid for blushing control requires further investigation.

Psychometrische Eigenschaften des Fragebogens zur Errötungsangst (FEA)

Der Fragebogen zur Errötungsangst (FEA) erfasst subjektiv wahrgenommenes Erröten und die Angst davor auf sieben nach klinischen Gesichtspunkten definierten Subskalen. Die psychometrischen Gütekriterienbestimmung erfolgte in drei Stichproben: 260 Studenten, 62 Errötungsängstliche und 71 Patienten mit Sozialer Angststörung mit Errötungsangst. Zur Konstruktvalidierung wurden die Variablen Soziale Ängstlichkeit, psychopathologische Symptombelastung, Selbstwert und Persönlichkeitsfaktoren erfasst. Die Subskalen wiesen überwiegend niedrige Skaleninterkorrelationen auf. Die interne Konsistenz war mit Ausnahme zweier Skalen zufrieden stellend (Cronbachs α ≥ .74), die Retest-Reliabilität mit einer Ausnahme gut (rtt ≥ .77). Die Konstruktvalidität variierte abhängig von den betrachteten Subskalen. Veränderungen durch Psychotherapie wurden sensitiv abgebildet. Studentische und klinische Stichproben konnten mittels Diskriminanzanalyse zu 90 % korrekt zugeordnet werden. Mittels ROC-Analyse wurde für die Subskala Errötungsangst ein Schwellenwert von 3.6 ermittelt. Angesichts guter psychometrischer Eigenschaften der Subskala Errötungsangst und gleichzeitiger Einschränkungen bei der Validierung einiger Teilskalen, wird je nach Verwendungszweck der Einsatz des FEA als Kurz- oder Langform vorgeschlagen.

Effect of task-related extracerebral circulation on diffuse optical tomography: experimental data and simulations on the forehead

The effect of task-related extracerebral circulatory changes on diffuse optical tomography (DOT) of brain activation was evaluated using experimental data from 14 healthy human subjects and computer simulations. Total hemoglobin responses to weekday-recitation, verbal-fluency, and hand-motor tasks were measured with a high-density optode grid placed on the forehead. The tasks caused varying levels of mental and physical stress, eliciting extracerebral circulatory changes that the reconstruction algorithm was unable to fully distinguish from cerebral hemodynamic changes, resulting in artifacts in the brain activation images. Crosstalk between intra- and extracranial layers was confirmed by the simulations. The extracerebral effects were attenuated by superficial signal regression and depended to some extent on the heart rate, thus allowing identification of hemodynamic changes related to brain activation during the verbal-fluency task. During the hand-motor task, the extracerebral component was stronger, making the separation less clear. DOT provides a tool for distinguishing extracerebral components from signals of cerebral origin. Especially in the case of strong task-related extracerebral circulatory changes, however, sophisticated reconstruction methods are needed to eliminate crosstalk artifacts.

Regional differences in facial skin blood flow responses to the cold pressor and static handgrip tests

We have previously reported the unique regional responses of facial skin blood flow (SkBF) to oral application of the basic tastes without simultaneous systemic circulatory changes. In the present study, we determined whether a systemic circulatory challenge due to sympathetic activation induces regional differences in facial SkBF by observing the responses in facial SkBF and blood pressure to a 2-min cold pressor test (CPT) and static handgrip exercise (HG) by right hand in 20 healthy subjects. The CPT significantly increased SkBF in the forehead, eyelid, cheek, upper lip and lower lip by 6 ± 2 to 8 ± 2 % (mean ± SEM) as compared to resting baseline, with a significant simultaneous increase (13 ± 2 %) in mean arterial pressure (MAP), whereas it significantly decreased the SkBF in the nose by 5 ± 2 %. The HG significantly increased SkBF in the forehead, cheek and lower lip by 6 ± 3 to 10 ± 3 %, with a significant simultaneous increase in MAP (13 ± 2 %), while it induced no significant change in the other regions. Increases in SkBF were greater in the right than left cheek during CPT. These results demonstrate that a systemic circulatory challenge via sympathetic activation elicits regional differences in the facial SkBF response.

The physiological origin of task-evoked systemic artefacts in functional near infrared spectroscopy

A major methodological challenge of functional near-infrared spectroscopy (fNIRS) is its high sensitivity to haemodynamic fluctuations in the scalp. Superficial fluctuations contribute on the one hand to the physiological noise of fNIRS, impairing the signal-to-noise ratio, and may on the other hand be erroneously attributed to cerebral changes, leading to false positives in fNIRS experiments. Here we explore the localisation, time course and physiological origin of task-evoked superficial signals in fNIRS and present a method to separate them from cortical signals. We used complementary fNIRS, fMRI, MR-angiography and peripheral physiological measurements (blood pressure, heart rate, skin conductance and skin blood flow) to study activation in the frontal lobe during a continuous performance task. The General Linear Model (GLM) was applied to analyse the fNIRS data, which included an additional predictor to account for systemic changes in the skin. We found that skin blood volume strongly depends on the cognitive state and that sources of task-evoked systemic signals in fNIRS are co-localized with veins draining the scalp. Task-evoked superficial artefacts were mainly observed in concentration changes of oxygenated haemoglobin and could be effectively separated from cerebral signals by GLM analysis. Based on temporal correlation of fNIRS and fMRI signals with peripheral physiological measurements we conclude that the physiological origin of the systemic artefact is a task-evoked sympathetic arterial vasoconstriction followed by a decrease in venous volume. Since changes in sympathetic outflow accompany almost any cognitive and emotional process, we expect scalp vessel artefacts to be present in a wide range of fNIRS settings used in neurocognitive research. Therefore a careful separation of fNIRS signals originating from activated brain and from scalp is a necessary precondition for unbiased fNIRS brain activation maps.

The effect of facial blood flow on ratings of blushing and negative affect during an embarrassing task: preliminary findings

Expecting to blush is a common source of social anxiety, and is associated with heightened perceptions of blushing and embarrassment. To assess whether sensory cues associated with heightened facial blood flow are an additional source of anxiety, the vasodilator niacin (100mg) or placebo was administered double-blind to 33 participants, and facial blood flow was investigated when they sang a children's song. Vasodilatation during singing was greater in the niacin than placebo condition, and niacin-evoked flushing and increases in pulse rate were greater in participants with high than low fear of negative evaluation. Nevertheless, ratings of embarrassment, anxiety, blushing and facial heat were similar in both drug conditions. This dissociation implies that cognitive appraisals or negative affect overrode more subtle physiological cues of blushing during embarrassment. Clarifying how judgments about blushing are made could be crucial for correcting faulty assumptions about blushing in people who are frightened of this response.

Blushing in rosacea sufferers

OBJECTIVE

Rosacea is characterized by extremely sensitive skin and persistent facial flushing, perhaps initiated or exacerbated by frequent or intense blushing. To investigate this, blushing was assessed in rosacea sufferers and controls during embarrassing laboratory tasks.

METHODS

Changes in forehead blood flow were monitored with laser Doppler fluxmetry in 31 rosacea sufferers (12 with severe symptoms and 19 with mild symptoms) and 86 controls while singing, giving an impromptu speech, and listening to recordings of these activities.

RESULTS

Changes in forehead blood flow were similar in rosacea sufferers and controls, and were similar in subgroups with mild and severe rosacea. Even so, rosacea sufferers thought that that they blushed more intensely and were more embarrassed than controls during most of the tasks. Likewise, changes in forehead blood flow were similar in participants with mild and severe rosacea. Nevertheless, ratings of embarrassment and blushing were greater in those with severe than mild symptoms. Within the rosacea group, increases in blood flow while singing were greatest in participants with the highest blushing ratings, whereas increases in blood flow while listening to the speech were greatest in the most embarrassed participants.

CONCLUSIONS

These findings do not support the hypothesis that blushing is abnormal in rosacea but, nevertheless, suggest that rosacea sufferers are more aware of and embarrassed by blushing than controls. This might contribute to social anxiety in rosacea sufferers.

Basic taste stimuli elicit unique responses in facial skin blood flow

Facial expression changes characteristically with the emotions induced by basic tastes in humans. We tested the hypothesis that the five basic tastes also elicit unique responses in facial skin blood flow. Facial skin blood flow was measured using laser speckle flowgraphy in 16 healthy subjects before and during the application of basic taste stimuli in the oral cavity for 20 s. The skin blood flow in the eyelid increased in response to sweet and umami taste stimuli, while that in the nose decreased in response to a bitter stimulus. There was a significant correlation between the subjective hedonic scores accompanying these taste stimuli and the above changes in skin blood flow. These results demonstrate that sweet, umami, and bitter tastes induce unique changes in facial skin blood flow that reflect subjective hedonic scores.

Oxygenated-blood colour change thresholds for perceived facial redness, health, and attractiveness

Blood oxygenation level is associated with cardiovascular fitness, and raising oxygenated blood colouration in human faces increases perceived health. The current study used a two-alternative forced choice (2AFC) psychophysics design to quantify the oxygenated blood colour (redness) change threshold required to affect perception of facial colour, health and attractiveness. Detection thresholds for colour judgments were lower than those for health and attractiveness, which did not differ. The results suggest redness preferences do not reflect a sensory bias, rather preferences may be based on accurate indications of health status. Furthermore, results suggest perceived health and attractiveness may be perceptually equivalent when they are assessed based on facial redness. Appearance-based motivation for lifestyle change can be effective; thus future studies could assess the degree to which cardiovascular fitness increases face redness and could quantify changes in aerobic exercise needed to increase facial attractiveness.

Blushing during social interactions in people with a fear of blushing

Changes in facial blood flow were investigated during an introductory conversation, delivering a speech, and listening to the speech afterwards in 16 people with a fear of blushing and 16 controls. It was hypothesized that fear of blushing would be associated with high ratings of self-reported blushing intensity and embarrassment during the tasks, and with persistence of the blushing reaction between tasks. Embarrassment and self-reported blushing intensity were greater in the fear-of-blushing group than in controls throughout the experiment. Increases in facial blood flow were similar in the two groups during each of the tasks. However, blushing dissipated more slowly after each task in the fear-of-blushing group than in controls, resulting in an incremental increase in facial blood flow over the course of the experiment. The slow recovery after an episode of blushing might result in physiological or social cues that help to maintain a fear of blushing.

Immersion of the hand in ice water releases adrenergic vasoconstrictor tone in the ipsilateral temple

Immersion of the hand in painfully cold water induces cutaneous vasodilatation in the temples, more so ipsilaterally than contralaterally. To investigate the mechanism of this response, guanethidine or saline was administered by transcutaneous iontophoresis to a recording site in the temple of ten participants before they immersed one of their hands in ice water. Guanethidine displaces noradrenaline from sympathetic nerve terminals and inhibits sympathetic noradrenergic neurotransmission. Therefore, it was hypothesized that guanethidine pre-treatment would block vasodilatation mediated by release of sympathetic vasoconstrictor tone in cutaneous vessels in the temple. During hand immersion, increases in the amplitude of the pulse waveform detected by laser Doppler flowmetry were greater in the ipsilateral than contralateral temple (86% vs. 34% above baseline, p<0.05), and pre-treatment with guanethidine prevented this asymmetric response (ipsilateral response 21% above baseline and contralateral response 32%, difference not significant). Guanethidine also inhibited ipsilateral increases in cutaneous blood flow during hand immersion in responsive participants. These findings suggest that limb pain inhibited ipsilateral adrenergic vasoconstrictor outflow in the temple. Thus, the findings challenge the concept of the sympathetic nervous system as a "mass action" system that discharges in unison to meet environmental demands. Instead, they suggest that the sympathetic nervous system is highly differentiated, with separate control of discrete reflex pathways on each side of the body.

Symptomatic treatment of idiopathic and rosacea-associated cutaneous flushing with propranolol

Flushing has been associated with medications, rosacea, menopause, carcinoid syndrome, pheochromocytoma, polycythemia, and mastocytosis, although it can occur without known cause. There are no known specific treatments available, but beta-blockers have suppressed flushing reactions in some patients, particularly when associated with anxiety. The medical histories and clinical characteristics of 9 patients with either idiopathic flushing or flushing associated with rosacea were reviewed. Eight patients experienced subjective improvement with propranolol therapy.

Do blushing phobics overestimate the undesirable communicative effects of their blushing?

Previous research indicated that blushing has socially threatening revealing effects in ambiguous situations. To explain blushing phobics' fearful preoccupation with blushing, we tested the hypothesis that blushing fearful individuals overestimate its revealing effects. High (n = 20) and low (n = 20) blushing fearful individuals read vignettes describing prototypical mishaps and ambiguous social events. Participants were prompted in the perspective of the actor, and were asked to indicate their expectations of the observers' judgments (meta-perceptions). Blushing fearful individuals overestimated the probability and the costs of undesirable outcomes. However, this judgmental bias was not inflated by displaying a blush. Thus, the results provide no evidence to support the idea that fear of blushing is fuelled by a biased conception of its communicative effects.

Personality, affective response, and facial blood flow during brief cognitive tasks

Blood pressure, heart rate, and changes in facial and finger blood flow were monitored in 58 women during three laboratory tasks, i.e., reading out a neutral text, a personally relevant speech (including a silent preparation phase), and a tracking task. Participants rated the tasks as mild to moderate with regard to affect intensity. Significant effects of personality on affect states were demonstrated, indicating higher levels of anxiety, depression, and anger in the high-neuroticism group, and more curiosity in the high-extraversion group. Arterial pressure, heart rate, and facial blood flow increased during task performance in all three conditions. No relationship between facial blood flow changes and muscle activity measured by m. masseter electromyography (EMG) were demonstrated. Digital vasoconstriction occurred in parallel with facial vasodilatation during tracking and in the preparation phase before the speech. There were no moderator effects of neuroticism or extraversion on blood flow or other cardiovascular responses.

Effects of repeated electrocutaneous pain stimulation on facial blood flow

The purpose of the study was to examine the effects of repeated electrocutaneous pain stimulation of the hand on facial blood flow responses in healthy human subjects (58 adult women). Finger blood flow, mean arterial blood pressure, and heart rate were also monitored. To investigate the influence of psychological factors, the subjects' affect states were assessed, and physiological responding was explored during cognitive distraction, i.e., when attention was turned away from the unpleasant stimulus. Consistently, electrocutaneous stimulation elicited vasodilatation in the cheek, together with finger vasoconstriction. This response pattern was evident even at non-painful stimulation intensities. The facial blood flow response showed habituation across stimulation trials and was largely unrelated to systemic cardiovascular changes, affect states, and attentional manipulation. These findings indicate (1) that the experimentally induced facial blood flow changes are part of a non-specific physiological response pattern elicited during noxious stimulation, and (2) that they are not dependent on regional (orofacial) stimulation for their occurrence.

Staring at one side of the face increases blood flow on that side of the face

To investigate the effect of observation on blushing, an experimenter sat next to 28 participants and looked closely at one cheek while the participant sang (embarrassing) or read aloud (not embarrassing). Increases in cheek temperature were greater on the observed than the unobserved side during both tasks. Changes in cheek temperature were symmetrical when the experimenter sat next to another 23 participants and looked straight ahead, as well as when the experimenter stared at one side of the participant's face through a glass window while the participant sang. However, increases in cutaneous blood flow were greater on the observed than the unobserved side of the forehead during singing. These findings suggest that staring at one side of the face triggers an ipsilateral increase in facial blood flow.

Embarrassment and social phobia: the role of parasympathetic activation

The few studies on the psychophysiology of embarrassment have suggested involvement of parasympathetic activation. However, blushing, the hallmark of embarrassment and a prominent symptom in social phobia, is more likely to be produced by cervical sympathetic outflow. Hitherto, there has been no evidence of parasympathetic innervation of the facial blood vessels. In this study, a group of social phobics and control participants watched, together with a 2-person audience, a previously made videotape of themselves singing a children's song. Self-report measures confirmed that this task induced embarrassment. While two measures of respiratory sinus arrhythmia (RSA) during the task did not indicate heightened parasympathetic tone, increased heart rate (HR) and skin conductance marked sympathetic activation. Thus, our data do not support the notion that an increase in parasympathetic activation plays a significant role in social phobia and embarrassment. Social anxiety and embarrassment both resulted in sympathetic activation.