Iwao Kanno

Changes in human cerebral blood flow and myocardial blood flow during mental stress measured by dual positron emission tomography

Mental stress causes a substantial sympathetic response, thus increasing myocardial blood flow (MBF). However, the effects of mental stress on global CBF have not been elucidated. In this study, changes in CBF and MBF in relation to mental stress were measured by a dual positron emission tomography system that can measure CBF and MBF simultaneously. CBF and MBF were measured in 10 healthy men with O-15 labeled water at rest (baseline) and during the performance of a mental task that required subtraction of 7s serially from a four-digit number. Baseline global CBF and values obtained during the mental activity were 0.42±0.05 and 0.45±0.06 ml/ml/min (mean±SD), respectively. Baseline MBF and values obtained during mental activity were 0.61±0.12 and 1.09 ±0.58 ml/ml/min, respectively. Percent changes in CBF and MBF during mental stress were 6±11% and 78±73%, respectively. No significant difference was observed in PaCO2 level between the mental stress and baseline conditions. MBF, blood pressure, heart rate, and plasma concentrations of adrenaline and noradrenaline increased significantly during mental stress. Sympathetic stimulation is reported to cause cerebral vasoconstriction and reduce CBF in animals. Although such a sympathetic response was observed in relation to mental stress, no significant change in CBF was observed in our subjects.

Quantitative aspects of changes in cerebral blood flow induced by neuronal activation

Abstract We examined the quantitative aspects of neurovascular coupling by revisiting and reanalyzing published cerebral blood flow (CBF) data, measured by positron emission tomography (PET) and laser Doppler flowmetry (LDF). The proportional increase of absolute CBF with the baseline CBF even under constant stimulation suggests that the CBF increase is independent of the nutritional demand induced by neuronal activity. In contrast, the linearity of the normalized CBF relative to the baseline CBF in PET and the linearity of the relative CBF to the frequency of electrical stimulation in LDF, both suggest that relative CBF change is beautifully regulated by the strength of neuronal activity. In addition, we will discuss the features of the two CBF regulation factors, PaCO2 and neuronal activity.

Evoked cerebral blood flow is linear to neuronal activation but independent of metabolic oxygen demand

Abstract The purpose of this study was to test the hypothesis that the degree of evoked local cerebral blood flow (LCBF) is dependent on neuronal activity, but not on oxygen consumption. We measured the field potential and evoked LCBF using laser-Doppler flowmetry in alpha-chloralose anesthetized rats during activation of the somatosensory cortex. The findings of this study are: (1) change in response magnitude of evoked LCBF reflects the change in the integrated amplitude of field potentials; (2) hyperoxia enhances the evoked LCBF; and (3) the evoked LCBF is proportional to the baseline flow. These suggest that the evoked LCBF is not directed toward supplying oxygen and some substrates for oxidative metabolism, but it could be modified by mechanisms operating on the blood vessels, which are proportional to neuronal activity.

Physiological basis for mapping brain activation through vascular response

Abstract Functional brain mapping signals arise mainly because of changes in cerebral blood flow (CBF) and metabolism induced by neuronal activation. This paper reviews the physiological basis for these signals. These secondary signals, in contrast to the primary, or electrophysiological, signal of neuronal activity, are used as a tool to map brain function during psychophysiological tasks and have been investigated in temporal, spatial and magnitude aspects using various measurement methods. The hemodynamic signal can be measured directly as CBF change, and indirectly through changes of the oxygenation level of the blood. In this article, quantitative attributes of the secondary signal are examined. The linearity between the strength of neuronal activity and the magnitude of the signal is tested using PET-CBF and perturbation of the physiological environment. Absolute CBF does not directly reflect neuronal activity, whereas relative CBF (absolute CBF-normalized so that global CBF is constant across subjects) revealed a tight correlation with neuronal activity.

Effects of Fragrance of Whiskey: An Electrophysiological Study

We have already shown [1] that the alpha wave power at a frequency of 10 Hz was greater for the fragrance of whiskey than for the fragrances of distilled water, ethanol, and nonmature whiskey. Therefore, it was assumed that the fragrance of mature whiskey can bring about a moderate resting state, i.e., a relaxed condition without drowsiness, in those who like it. We have also demonstrated that the fragrance of whiskey can influence the rate of information processing in the brain. In the present study, we measured the regional cerebral blood flow (rCBF) of the limbic system, including the olfactory and the auditory systems, in ten subjects while they performed an auditory oddball task in the presence of an ambient fragrance. Event-related potentials (ERPs) were also recorded during the same task.

Cerebral Blood Volume Reactivity to Hypercapnia Measured by 11C-Labeled Carboxyhemoglobin and Positron Emission Tomography

The purpose of this study was to examine regional reactivity of cerebral blood volume (CBV) to changes in PaCO2. CBV was measured using an 11COinhalation method and positron emission tomography (PET) [1].