Relationship Between Cerebral Blood Oxygenation and Electrical Activity During Mental Stress Tasks: Simultaneous Measurements of NIRS and EEG

Stress Reduction Effects during Block-Tapping Task of Jaw in Healthy Participants: Functional Near-Infrared Spectroscopy (fNIRS) Measurements of Prefrontal Cortex Activity

The purpose of this study was to explore the influence of simple jaw opening and closing task of chewing movements on the activities of the prefrontal cortex (PFC) from the viewpoint of stress reduction. We measured cerebral blood flow (CBF) in the PFC during a block-tapping task of the jaw in healthy participants. Eleven young healthy individuals with normal dentition (7 males and 4 females, mean age 28.0 ± 3.7 years) volunteered for this study. CBF was measured using a wearable, functional near-infrared spectroscopy device. Measurements were taken using the central incisors and first molars at interocclusal distances of 5 and 10 mm. The participants were asked to bite a hard/soft block. CBF in all conditions showed limited variability or decreasing trend compared to resting state before the task. The main effect was observed for interocclusal distance (p = 0.008), and there were no significant differences for measurement area of the PFC, tooth type, and material type. An interaction was found between tooth type and material type. In conclusion, these results suggest that simple and rhythmical chewing motion has an effect of reducing CBF in the PFC and resting the PFC, which is an especially notable aspect of periodontal sensory information in the molar.

Stress Evaluation by Hemoglobin Concentration Change Using Mobile NIRS

Previous studies have reported a relationship between stress and brain activity, and stress has been quantitatively evaluated using near-infrared spectroscopy (NIRS). In the present study, we examined whether a relationship exists between salivary amylase levels and brain activity during the trail-making test (TMT) using mobile NIRS. This study aimed to assess stress levels by using mobile NIRS. Salivary amylase was measured with a salivary amylase monitor, and hemoglobin concentration was measured using Neu’s HOT-2000. Measurements were taken four times for each subject, and the values at each measurement were evaluated. Changes in the values at the first–second, second–third, and third–fourth measurements were also analyzed. Results showed that the value of the fluctuations has a higher correlation than the comparison of point values. These results suggest that the accuracy of stress assessment by NIRS can be improved by using variability and time-series data compared with stress assessment using NIRS at a single time point.

Cardiac output and cerebral blood flow during carotid surgery in regional versus general anesthesia: A prospective randomized controlled study

OBJECTIVE

Carotid endarterectomy (CEA) is a preventive procedure aimed at decreasing the subsequent risk of fatal or disabling stroke in patients with significant carotid stenosis. It is well-known that carotid surgery under ultrasound-guided regional anesthesia (US-RA) causes a significant increase in blood pressure, heart rate and stress hormone levels owing to increased sympathetic activity. However, little is known about the effects on cardiac output (CO), cardiac index (CI), and cerebral blood flow (CBF) under US-RA as compared with general anesthesia (GA).

METHODS

Patients scheduled for CEA were randomized prospectively to receive US-RA (n = 37) or GA (n = 41). The primary end point was the change in CI after induction of anesthesia and the change from baseline over time at four different times during the entire procedure in the respective randomized US-RA and GA groups. In addition to systolic blood pressure and heart rate, we also recorded peak systolic velocity, end-diastolic velocity, and minimum diastolic velocity as seen from transcranial Doppler ultrasound examination, as well as regional cerebral oxygenation (rSO₂) as seen from near-infrared refracted spectroscopy to evaluate cerebral blood flow.

RESULTS

In the US-RA group, the CI increased after induction of anesthesia (3.7 ± 0.8 L/min/m²) and remained constant until the end of the procedure. In the GA group CI was significantly lower (2.4 ± 0.6 L/min/m²; P < .001). After induction of anesthesia, the rSO₂ remained constant in the GA group on both the ipsilateral (63 ± 9 rSO₂) and the contralateral (65 ± 7 rSO₂) sides; in contrast, it significantly increased in the US-RA group (ipsilateral 72 ± 8 rSO₂; P < .001; contralateral 72 ± 6 rSO₂; P < .001). The transcranial Doppler ultrasound parameters (peak systolic velocity, end-diastolic velocity, and minimum diastolic velocity) did not differ between the US-RA and the GA group. The clinical outcome was similarly favorable for both groups.

CONCLUSIONS

CI was maintained near baseline values throughout the procedure during US-RA, whereas a significant decrease in CI values was observed during CEA under GA. Near-infrared refracted spectroscopy values, reflecting blood flow in small vessels, were higher in US-RA patients than in those with GA. These differences did not influence clinical outcome.

Evaluation of olive oil effects on human stress response by measuring cerebral blood flow

In this paper, we evaluated the effects of olive oil on human's stress level. In recent years, mental stress from harsh working environment have been causing serious problems to human health, both mentally and physically. Symptoms of stress may include feelings of worthlessness, agitation, anxiety, lethargy, insomnia, and behavioral changes. Additionally, the harsh working environments may cause the workers to adopt unhealthy dietary habits, contributing to the health issue. On the other hand, olive oil has been known to provide stress-relieving effects both by ingestion and by inhaling the scent. Here, we examined the effects of extravirgin olive oil ingestion for mitigating stress from deskwork. Three best-selling extravirgin olive oil in Japan were tested, and typing task was selected to emulate deskwork situation. Near-infrared spectroscopy (NIRS) is utilized in this study to visualize the response in brain via cerebral blood flow analysis and to measure participants' stress level. Statistical analysis showed that the stress levels were lower during the olive oil ingestion experiment compared to no-oil experiment, even when measured one hour after the ingestion.