Ginkobiloba extract improves working memory performance in middle-aged women: role of asymmetry of prefrontal cortex activity during a working memory task.

In order to clarify the mechanism through which extract of Ginkgo biloba leaves (EGb) improves cognitive function, we examined the effects of EGb on cerebral blood oxygenation in the prefrontal cortex (PFC) and on performance during a working memory task, using near-infrared spectrometry (NIRS). First, we evaluated differences in behavioral performance of the Sternberg working memory test (ST) and in the activation pattern of the PFC during ST between 15 young and 19 middle-aged healthy women. Then, we examined the effect of EGb (120 mg/day for 6 weeks) on ST performance and PFC activation pattern in the middle-aged group. The middle-aged group exhibited a longer reaction time (RT) in ST than the young group and showed a different PFC activation pattern during ST, i.e., the middle-aged group showed bilateral activation while the young group showed right-dominant activation. In the middle-aged group, administration of EGb for 6 weeks shortened the RT of ST and changed the PFC activation pattern to right-dominant, like that in the young group. The results indicate the PFC plays a role in the physiological cognitive function-enhancing effect of EGb. EGb might improve working memory function in middle-aged individuals by counteracting the occurrence of aging-related hemispheric asymmetry reduction.

Relation between working memory performance and evoked cerebral blood oxygenation changes in the prefrontal cortex evaluated by quantitative time-resolved near-infrared spectroscopy.

OBJECTIVES: The lateral prefrontal cortex (LPFC) plays a central role in working memory (WM). In the present study, we employed quantitative, near-infrared time-resolved spectroscopy (TRS) to evaluate the relation between LPFC activity during WM and the task performance in 19 healthy, middle-aged, female subjects (mean age of 46·8±2·1 years). METHODS: Concentration changes of oxyhemoglobin (oxy-Hb), deoxyhemoglobin, and total hemoglobin in the bilateral LPFC were measured by means of TRS during performance of Sternberg tests (ST) of one digit and six digits. The oxy-Hb changes were compared to performance in ST. In addition, we evaluated whether pathlength of the forehead and baseline concentration of oxy-Hb influenced WM performance. RESULTS: TRS revealed increases in oxy-Hb in association with a decrease in deoxy-Hb during ST. We found a significant negative correlation between the reaction time of six-digit ST and oxy-Hb changes in the bilateral LPFC (left, P = 0·0061; right, P = 0·0029); however, no significant correlation was observed with one-digit ST. In contrast, accuracy of ST did not correlate with the oxy-Hb changes in the prefrontal cortex. The optical pathlength of the forehead and concentration of oxy-Hb at rest in the LPFC did not correlate with either reaction time or accuracy in ST. CONCLUSION: The present results indicate that oxy-Hb changes in the LPFC during a WM task, as measured by TRS, correlated with WM performance. TRS is compact and less expensive than functional magnetic resonance imaging, and may be a useful tool to evaluate neural correlates of WM in normal adults.

Effects of aging on activity of the prefrontal cortex and autonomic nervous system during mental stress task.

We evaluated the effect of aging on the prefrontal cortex (PFC) activity and heart rate during the task. Employing near infrared spectroscopy (NIRS), we measured hemoglobin concentration changes in the bilateral PFC during a mental arithmetic task in young and older females. We selected the subjects who exhibited an increase in oxyhemoglobin with a decrease in deoxyhemoglobin during the task. We observed that right PFC activity predominantly modulates sympathetic effects during the task in both groups. However, the changes of oxyhemoglobin and heart rate during the task in older subjects were significantly smaller than those in young subjects. These results indicate that aging affects evoked cerebral blood oxygenation (CBO) response patterns of the PFC during a mental stress task. Aging did not affect the laterality of PFC activity in modulation of ANS function in the subjects who exhibited increases of oxyhemoglobin and deoxyhemoglobin associated with a decrease of deoxyhemoglobin during the task. However, aging reduced the heart rate increase during the task.

Effects of fragrance administration on stress-induced prefrontal cortex activity and sebum secretion in the facial skin.

Although fragrances have long been known to influence stress-induced psychosomatic disorders, the neurophysiological mechanism remains unclear. We evaluated the effect of fragrance on the relation between the level of sebum secretion in the facial skin and the stress-induced prefrontal cortex (PFC) activity, which regulates the activity of the hypothalamic-pituitary-adrenal axis. Employing near infrared spectroscopy, we measured hemoglobin concentration changes in the bilateral PFC during a mental arithmetic task in normal adults (n=31), and evaluated asymmetry of the PFC activity in terms of the laterality index (i.e., [(right-left)/(right+left)]) of oxyhemoglobin concentration changes (LI-oxyHb). We measured the level of sebum secretion in the facial skin before the task performance. There was a significant positive correlation between the LI-oxyHb and the level of sebum secretion (r=+0.44, p=0.01). We selected the subjects who exhibited high levels of sebum secretion and right-dominant PFC activity for the study on the fragrance effect (n=12). Administration of fragrance for four weeks significantly reduced the level of sebum (p=0.02) in the fragrance group (n=6). In addition, the LI-oxyHb decreased significantly from 0.11+/-0.07 to -0.10+/-0.18 (p=0.01), indicating that the dominant side of the stress-induced PFC activity changed from the right to left side. In contrast, neither LI-oxyHb nor the levels of sebum secretion changed significantly in the control group (n=6). These results suggest that administration of fragrance reduced the level of sebum secretion by modulating the stress-induced PFC activity. The PFC may be involved in the neurophysiological mechanism of fragrance effects on systemic response to mental stress.

Relation between mental stress-induced prefrontal cortex activity and skin conditions: a near-infrared spectroscopy study.

Although psychological stress affects skin condition, the neurophysiological mechanism involved is unclear. In this study, we evaluated the relationship between skin condition and left/right asymmetry in prefrontal cortex (PFC) activity during mental stress tasks since recent studies have suggested that the right PFC dominates the regulation of the stress response system, including the hypothalamic-pituitary-adrenal (HPA) axis. Using near-infrared spectroscopy, we measured hemoglobin concentration changes in the bilateral PFC during a mental arithmetic task in normal adults and evaluated the laterality scores (i.e., [(right-left)/(right+left)]) of oxyhemoglobin concentration changes. Elicitation of stress was verified by the State-Trait Anxiety Inventory (STAI) and heart rate. The sebum levels and Propionibacterium acnes populations in the facial skin were measured before the task. The task significantly increased the STAI-II scores (p=0.00079) and heart rate (p=0.0000049). The oxyhemoglobin concentration increased in the bilateral PFC during the task, associated with a decrease in deoxyhemoglobin concentration. The laterality scores of oxyhemoglobin concentration changes were positively correlated with sebum levels (r=+0.50, p=0.026) and P. acnes populations (r=+0.49, p=0.029) in the facial skin before the task. There was a significant positive correlation between heart rate changes and the laterality scores of oxyhemoglobin concentration changes (r=+0.54, p=0.015). These results demonstrate that the subjects with higher sebum levels and higher P. acnes populations in the facial skin have a right dominant PFC activity during a mental stress task and suggest that such subjects are sensitive to mental stress associated with hyperactivity of the stress response system, including the HPA axis system.

Relation between asymmetry of prefrontal cortex activities and the autonomic nervous system during a mental arithmetic task: near infrared spectroscopy study.

The present study evaluated the relationship between asymmetry of the prefrontal cortex activity and the automatic nervous system (ANS) response during a mental arithmetic (MA) task. Employing near infrared spectroscopy, we compared cerebral blood oxygenation changes in the right and left prefrontal cortices during a mental arithmetic task with HR changes. During the MA task, eight subjects (high-HR group) showed large HR increases (14.2 +/- 3.0) while eight subjects (low-HR group) showed small HR increases (3.6 +/- 2.8) (P < 0.00001). In both the high-HR and low-HR groups, near infrared spectroscopy (NIRS) demonstrated increases of oxyhemoglobin and total hemoglobin (=oxyhemoglobin + deoxyhemoglobin) associated with decreases of deoxyhemoglobin in the bilateral prefrontal cortices during MA task. In the high-HR group, the laterality ratio scores, i.e., [(R - L)/(R + L) of oxyhemoglobin and total hemoglobin], showed positive values (0.17 +/- 0.11 and 0.17 +/- 0.17, respectively), while in the low-HR group, the laterality ratio scores showed negative values (-0.28 +/- 0.21 and -0.35 +/- 0.24, respectively). In addition, there were significant positive correlations between HR changes and the laterality ratio scores of oxyhemoglobin (r = +0.87, P < 0.0001) and total hemoglobin (r = +0.85, P < 0.0001). These results indicate that the MA task-induced activity in the right prefrontal cortex was larger than that in the left prefrontal cortex in the subject with high HR increases, suggesting that the right prefrontal cortex activity during the MA task has a greater role in cerebral regulation of HR by virtue of decreasing parasympathetic effects or increasing sympathetic effects.

Regulation of plasma substance P and skin mast cells by odorants.

BACKGROUND: Mast cells stimulate inflammation and itch sensation in the skin by releasing various mediators when they are activated. Stress exacerbates some skin diseases. We have reported that inhalation of certain odorants modulates immune reactions in the skin. OBJECTIVE: The possible usage of odorants in the regulation of skin inflammation and itch sensation was to be examined. METHODS: Female volunteers were subjected to interview stress with or without odorant inhalation. Mice were immobilized while inhaling odorants. Toluidene blue-stained sections were analyzed for activated mast cells. Plasma substance P level was determined by enzyme-linked immunoassay. RESULTS: Interview stress induced plasma substance P only in volunteers who did not inhale odorants containing 2% 1,3-dimethoxy-5-methyl benzene (DMMB). Immobilization stress induced mast cell activation in mice and the activation was blocked by exposure to DMMB. CONCLUSIONS: Stress causes mast cell activation via an increase in substance P. The effect of stress is suppressed by inhalation of DMMB.