Mitsuo Tonoike

Frontal midline theta rhythms reflect alternative activation of prefrontal cortex and anterior cingulate cortex in humans

Frontal midline theta rhythm (Fm theta) often appears on electroencephalogram (EEG) during consecutive mental tasks. To clarify the source of rhythmic activity, magnetoencephalogram (MEG) and EEG were simultaneously measured in six healthy volunteers during different mental tasks using whole head MEG system. MEG records were averaged every one cycle of Fm theta rhythms using individual positive peaks of Fm theta waves in Fz EEG as a trigger. Averaged theta components of MEG signals were analyzed with a multi-dipole model. Two sources were estimated to the regions both of the prefrontal-medial superficial cortex and anterior cingulate cortex (ACC). These regions were alternatively activated in about 40 to 120 degrees phase shift during one Fm theta cycle. From above results, we hypothesize that appearance of Fm theta during consecutive mental tasks reflects alternative activities of the medial prefrontal cortex and ACC.

Ipsilateral Dominance of Human Olfactory Activated Centers Estimated from Event‐Related Magnetic Fields Measured By 122‐Channel Whole‐Head Neuromagnetometer Using Odorant Stimuli Synchronized with Respirations

ABSTRACT: The aim of this study was to measure and analyze olfactory event‐related magnetic fields using a whole‐cortex biomagnetometer (122‐channel SQUID gradiometer). Amyl‐acetate gas (approx. 1%) was administered for 300 msec into either the right or left nostril in synchronization with respiration using a mask and an optical fiber sensor. Clear olfactory event‐related magnetic fields were asymmetrically obtained on both sides of the forehead in all six subjects. The generators of olfactory magnetic fields were estimated at two regions located fairly asymmetrivally near the bilateral frontal deep areas. The goodness‐of‐fit was better for the two‐dipole model than the one‐dipole model in all experiments.

Local distribution of odor responsivities of mouse olfactory receptor neurons

The local distribution of odor responsivity was studied in isolated mouse olfactory neurons retaining their original spatial relationships in intact tissue. The selectivity for three odorants and population of responsive cells were estimated from the odor-induced increase in cytoplasmic calcium. It was found that cells with different odor selectivities coexisted with a shorter distance than cells of the same type. Cells with a similar odor responsivity were arranged somewhat more densely than a complete random distribution. The results indicated the coexistence of different subtypes of odor responsive cells in the septal epithelium with sparse clustering of similarly responsive cells.

Olfactory Event-Related Potentials and Olfactory Neuromagnetic Fields in Humans

It is very important to measure human olfactory responses noninvasively to determine their origins and deficiencies accurately. Olfactory evoked potentials have been investigated since 1966–1976 by Finkenzeller [1] and Allison and Goff [2]. Plattig [3], Kobal [4], and Hummel [5] have reported recording chemosensory evoked potentials. We [6,7] have also measured olfactory event-related potentials using an odorant pulse synchronized with subject respiration. However, these studies have provoked controversial discussion.

Analyses of gustatory-related brain magnetic fields induced by taste sensation

Abstract Recent studies on noninvasive recordings from human brain have shown the existence of taste-elicited activation areas in the cerebral cortex. While functional MRI (f-MRI) and positron CT (PET) are often used for these studies, the magnetoencephalogram (MEG) is the most commonly used instrument for these noninvasive measurements. One advantage of the MEG measurements is the ability to measure rapid taste-elicited time-course data. In this current study, we used brain magnetic fields to quantitate the stimulus latencies evoked by different taste stimuli that use different peripheral transduction mechanisms. Recent work has shown that taste stimuli that presumably act through different transduction processes show different MEG-measured latencies. Here, we measured the latencies due to citric acid and sucrose and compared these with the latency due to the action of the taste-modifying substance contained in miracle fruit during stimulation by citric acid. Miracle fruit has the property of changing the sour taste of acids to sweet taste. The use of this taste-modifying substance allows us to compare the latency of two very different sweet-taste-evoking substances.

Study of Olfactory Transduction by Analysis of Dynamics of Odor-Induced [Ca2+]i Increases in Receptor Neurons

The regulation of odor-induced changes in cytosolic free Ca2+ ([Ca2+]i) and odor-responsiveness was studied by analyzing the dynamics of the fluorescence intensity of intracellular fura-2 in the knobs and/or somata of isolated olfactory receptor neurons. Isolated olfactory receptor cells were enzymatically obtained from the olfactory epithelia of wild bullfrog or newt anesthetized with MS-222, or from an adult female mouse anesthetized with Ketalar 50, using the tissue-printing method. Fura-2 was loaded to isolated cells by incubation with fura-2/AM solution. The measurement of [Ca2+]i was carried out at seven positions, as described in our previous reports [1,2]. Odorants dissolved in normal Ringer’s solution (NR) were applied to the cells by perfusion of the bath solution.

Optical Recordings of Calcium Responses in Neighboring Olfactory Receptors Suggest that the Distribution of Subtypes of Receptors is Heterogeneous

The cellular distribution of odor responsiveness in the olfactory epithelium is unclear. To obtain evidence for this distribution, we examined the odorant responsiveness of neighboring olfactory receptor neurons in mouse and frog. Using our new isolation method, “tissue printing” [1], we prepared samples in which many neurons were isolated while their original spatial relationship in intact tissue was retained. The enzymes used in the isolation procedure were papain (1 mg/ml, 5–10 min, for frog) and trypsin (0.025%, 12 min, for mouse). We made measurements of cytoplasmic free calcium concentration ([Ca2+]i) in isolated neurons, using the Ca2+ indicator dye, fura-2. The fluorescence intensity of fura-2 was recorded in the somata of several cells within the optical field of view (210 × 235 µm2) at \(\tfrac{1}{3}\)-s intervals. Each fluorescence intensity was the integrated value of 5 × 5 pixels (2 × 2.4 µm2 on a cell) in eight video frames (\(\tfrac{1}{{30}}\)-s intervals). The odor stimulus solutions used were: citralva (CT; 100µM), isoamyl acetate (AM; 10 mM), pyrazine (PY; 1 mM), and several fatty acids in normal Ringer’s solution. Cell viability and physiological intactness were confirmed by among others, determining the responses to high concentration potassium solution and forskolin, determining the stable resting level of [Ca2]i, and investigating cell morphology.

Topographic Analysis of Hemispheric Differences in Chemosensory Event-Related Potentials

The aim of this study was to analyze chemosensory event-related potentials (CHERPs), to show the origin of their peaks, and also to examine hemispheric differences in responses to odorants and differences in subjects by using topographic mapping. CHERPs were measured by our blast method, in which an odorant gas is administered directly into the nasal cavity by inserting a thin Teflon tube in synchronization with the subject’s respiration [1,2].

Olfactory Response to an Inorganic Metal Compound

Inorganic metal compounds are generally thought of as odorless since they do not meet the criteria of odorific substances, which are those that have vapor pressure and dissolve in water or lipids. In this study, we measured the changes in cytosolic free Ca2+ concentration in isolated murine olfactory cells and the changes in olfactory event related potentials (ERPs) in humans, and analyzed these to determine whether an inorganic metal compound, e.g., aluminum hydroxide, Al(OH)3, could be physiologically recognized as having an odor.

An Olfactory Stimulation Method Using Non-magnetized Materials and The Measurement of Olfactory Neuromagnetic Response

1. 研 究 の 日的 感 覚 計 測 の 中 で嗅 覚 ・味 覚 の 計 測 は 遅 れ て い た が 、我 々 は嗅 覚 を客 観 的 に 計 測 す るた め 脳 波 に よる研 究 を 開 発 ・推 進 して き た。 こ の結 果 、 人 間 の 嗅 感 覚 に対 応 す る客 観 的 生 理 的 応 答 が脳 波 か ら得 られ る こ とが 明 らか と な り、 この 手法 は 、 遅 れ てい た嗅 覚 ・味 覚 の 研 究 を急 速 に発 展 させ て き た。 しか し、今日 、 人 間 の 特 性 を一 層 科 学 的 ・ 客 観 的 に解 明 す る こ とが 求 め られ 、生 体 を無 侵 襲 に 且 つ よ り高 精 度 に計 測 す る こ とが 必 要 で あ る。 そ こ で 、 我 々 は極 め て高 感 度 で あ る 超 伝 導量 子干 渉 素子(SQUID)を 川 い て人 間 の嗅 覚 刺 激 に対 す る応 答 を脳 の 磁 界 反 応 で捉 え る 手 法 を 開発 して い る。 本 報 告 で は 、非 磁 性 材 料 を川 い た 新 嗅 覚 刺 激 法 とDC-SQUIDに よる 嗅 覚脳 磁 波 計 測 につ い て述 べ る。