Kaoru Kohyama

Three-dimensional probabilistic anatomical cranio-cerebral correlation via the international 10–20 system oriented for transcranial functional brain mapping

The recent advent of multichannel near-infrared spectroscopy (NIRS) has expanded its technical potential for human brain mapping. However, NIRS measurement has a technical drawback in that it measures cortical activities from the head surface without anatomical information of the object to be measured. This problem is also found in transcranial magnetic stimulation (TMS) that transcranially activates or inactivates the cortical surface. To overcome this drawback, we examined cranio-cerebral correlation using magnetic resonance imaging (MRI) via the guidance of the international 10-20 system for electrode placement, which had originally been developed for electroencephalography. We projected the 10-20 standard cranial positions over the cerebral cortical surface. After examining the cranio-cerebral correspondence for 17 healthy adults, we normalized the 10-20 cortical projection points of the subjects to the standard Montreal Neurological Institute (MNI) and Talairach stereotactic coordinates and obtained their probabilistic distributions. We also expressed the anatomical structures for the 10-20 cortical projection points probabilistically. Next, we examined the distance between the cortical surface and the head surface along the scalp and created a cortical surface depth map. We found that the locations of 10-20 cortical projection points in the standard MNI or Talairach space could be estimated with an average standard deviation of 8 mm. This study provided an initial step toward establishing a three-dimensional probabilistic anatomical platform that enables intra- and intermodal comparisons of NIRS and TMS brain imaging data.

Multimodal assessment of cortical activation during apple peeling by NIRS and fMRI

An intriguing application of neuroimaging is directly measuring actual human brain activities during daily living. To this end, we investigated cortical activation patterns during apple peeling. We first conducted a pilot study to assess the activation pattern of the whole lateral cortical surface during apple peeling by multichannel near-infrared spectroscopy (NIRS) and detected substantial activation in the prefrontal region in addition to expected activations extending over the motor, premotor and supplementary motor areas. We next examined cortical activation during mock apple peeling by simultaneous measurement using multichannel NIRS and functional magnetic resonance imaging (fMRI) in four subjects. We detected activations extending over the motor, premotor and supplementary motor areas, but not in the prefrontal cortex. Thus, we finally focused on the prefrontal cortex and examined its activation during apple peeling in 12 subjects using a multichannel NIRS. We subsequently found that regional concentrations of oxygenated hemoglobin significantly increased in the measured region, which encompassed portions of the dorsolateral, ventrolateral and frontopolar areas of the prefrontal cortex. The current study demonstrated that apple peeling as practiced in daily life recruited the prefrontal cortex but that such activation might not be detected for less laborious mock apple peeling that can be performed in an fMRI environment. We suggest the importance of cortical study of an everyday task as it is but not as a simplified form; we also suggest the validity of NIRS for this purpose. Studies on everyday tasks may serve as stepping stone toward understanding human activities in terms of cortical activations.

Prefrontal activity during taste encoding: an fNIRS study.

To elucidate the function of the lateral prefrontal cortex (LPFC) in taste encoding, it is worth applying to taste, the psychological paradigms of intentional memorization that have been used with other extensively studied senses, and thus updating current models for LPFC functions to include a taste modality. Using multichannel functional near-infrared spectroscopy (fNIRS), we examined the LPFCs of healthy volunteers (N = 18) during the intentional memorization of a basic taste. In order to minimize the confounding effects of verbal processes that are known to employ the left LPFC, we used quaternary taste mixtures that were difficult to verbalize, and confined analysis to those who did not use a verbal strategy during memorization (N = 10). In order to examine the results in association with data in the literature, the location of activity was probabilistically estimated and anatomically labeled in the Montreal Neurological Institute (MNI) standard brain space. By contrasting the cortical activation under encoding conditions with that under control conditions without memory requirement, we found activation in the bilateral ventro-LPFC and the right posterior portion of the LPFC. The activation pattern was consistent with previous studies on the encoding of nonverbal materials using other senses. This suggests that models for LPFC functions that derive from previous studies can be generalized to intentional encoding processes of taste information, at least at a macro-structural level. The current study also demonstrates that, by using fNIRS, LPFC functions on taste can be examined with experimental paradigms relevant to those used for other senses.

A mixed system composed of different molecular weights konjac glucomannan and kappa carrageenan: large deformation and dynamic viscoelastic study

Abstract Rheological properties of mixed gels of konjac glucomannan (KGM) of four different molecular weights with kappa-carrageenan (CAR) were studied by dynamic viscoelastic measurements and tensile testing. Both storage and loss moduli for sol and gel state mixtures containing higher molecular weight KGM were highest. However variation in molecular weight of KGM produced little effect on the gel-to-sol and sol-to-gel transition temperatures of the mixtures. Two systems containing KGM of lower molecular weights showed almost the same stress—strain curves in tensile testing. The breaking stress and the breaking strain for mixed gels became larger with increasing molecular weight of KGM, and the difference was larger than that observed in the dynamic viscoelasticity measurements. It was suggested that weak junction zones are created by the addition of KGM and that the number of weak junction zones and the contour length of flexible chains connecting these weak junction zones increase with increasing molecular weight of KGM.

Mastication Effort Estimated by Electromyography for Cooked Rice of Differing Water Content

The objective of this study was to quantify the mastication effort for cooked rice. We analyzed mastication patterns while normal subjects ate a spoonful of cooked rice that had been prepared by cooking with different amounts of water (1.5, 2.0, 3.0, and 4.0 times the water to rice weight). The rice samples were served with the same weight, same volume and same solid content, and electromyography (EMG) of the masticatory muscles was measured. The texture of the four cooked rice samples was instrumentally analyzed by the two-bite method. The number of chews, masticatory time, and jaw-closing muscle activities per chew evaluated by EMG were higher in the rice sample cooked with least water, which exhibited a high firmness value in the instrumental test. Rice cooked with 4.0 times the amount of water exhibited the longest jaw-opening duration, which was related to the adhesiveness value in the instrumental test. The ratio of jaw-opening muscle activity to the preceding jaw-closing muscle activity was lower for the rice containing least water, this corresponding to the area ratio (balance degree) in the instrumental test. Softer rice containing more water reduced the total mastication effort until swallowing because it required a shorter mastication time. It was not difficult for the softer rice with high density to be ingested in greater weight, decreasing the mastication effort for a certain amount.

Effects of Environmental Temperature on Structure and Gelatinization Properties of Wheat Starch

ABSTRACT The effects of environmental temperature on gelatinization properties and amylopectin structures of wheat endosperm starch were examined by isolating starches from four wheat cultivars matured in growth chambers at daytime temperatures of 15, 20, 25, or 30°C. Kernel weight and starch content per kernel were reduced by high maturation temperature. Amylose content showed no significant change at high maturation temperature in some cultivars; in other cultivars, there was a slight increase. Principal component analysis of data on relative peak areas of debranched amylopectin showed that amylopectin from wheat grown at a lower temperature had a greater proportion of shorter chains. Amylopectin branch chains were classified into three groups based on the correlation coefficients between the data of branch chain length distribution and principal component scores, degree of polymerization (DP) of 6–12, DP 13–34, and DP ≥ 35. The gelatinization temperature of starches increased markedly at a higher matur...

Characterization of Food Physical Properties by the Mastication Parameters Measured by Electromyography of the Jaw-Closing Muscles and Mandibular Kinematics in Young Adults

The relationship between the physical properties of solid food and the masticatory parameters is clarified. Eight solid foods of varying physical properties were chosen. Electromyography of the jaw-closing muscles and mandibular kinematics in eleven young subjects were recorded. The masticatory parameters were derived from the recorded data for the entire mastication process, for the first bite, and in the early, middle, and late stages of mastication. After calculating values relative to the mean value for each subject, nine parameters representing each group were chosen through a cluster analysis. Three principal components were extracted, each of them related to the masticatory time and cycle, minimum jaw opening at the early stage of mastication, and masticatory force. The principal component scores for each food were different, except for one combination in which the physical properties under large and extra-large deformations were similar, despite different breaking properties or small deformation properties. The masticatory parameters did not correlate with the physical properties of food measured for small deformation.

A mixed system composed of different molecular weights konjac glucomannan and κ-carrageenan. II. Molecular weight dependence of viscoelasticity and thermal properties

Abstract Rheological and thermal properties for 5:5 mixed gels of konjac glucomannan (KGM) with five different molecular weights and κ-carrageenan (CAR) were studied. Molecular weight distribution was analysed by gel permeation chromatography (GPC). Dynamic and static viscoelastic moduli for the mixed gels were much smaller than those for gels of CAR alone and became larger with increasing molecular weight of KGM. Gel—sol transition for mixed systems with total gum content 1.5% w/w occurred at the temperatures between the transition temperature for 0.75% w/w CAR and that for 1.5% w/w CAR. Gel-to-sol and sol-to-gel transition temperatures for the mixed systems were slightly increased with increasing molecular weight of KGM in the mixture observed in differential scanning calorimetry (DSC). One exothermic peak was observed in cooling DSC curves, while two endothermic peaks appeared in heating DSC curves for 5:5 mixed systems. The intensity of the lower peak increased with increasing KGM proportion in the mixture and with increasing molecular weight of KGM at a given mixing ratio. This fact confirms that the mixed gels involve two crystalline regions: some are made by CAR molecules in the helical structure and others are formed by the interaction between helical CAR and KGM. On heating, the latter is broken at a lower temperature and then the former melts at a higher temperature. The junction zone formed by CAR and KGM is easily made in a gel containing KGM with a higher molecular weight or in a higher ratio to CAR, or a system of lower total gum content.

Textural evaluation of rice cake by chewing and swallowing measurements on human subjects

The difficulty in masticating and swallowing rice cake was quantified. Healthy subjects ate pieces of rice cake (9 g and 3 g) and a modified product (9 g). We used electromyography to measure the activity of the jaw-closing and -opening muscles during chewing, as well as the suprahyoid muscle activity, laryngeal movement, and sound during swallowing. The smaller the rice cake, the shorter the mastication time, the fewer the number of chews, and the less the jaw-closing muscle activity. A modified rice cake product (9 g) was consumed with less mastication effort than the standard rice cake (9 g) and with the same effort as the standard (3 g). Both the sample amount and texture influenced mastication, although neither factor caused a significant difference in swallowing characteristics. These observations suggest that swallowing was induced when the bolus properties became suitable for swallowing, as healthy subjects could adjust their mastication technique according to the food amount and texture.

Rheological study on the rennet-induced gelation of casein micelles with different sizes

Abstract Casein forms a gel in the presence of rennet. Kappa-casein existing on the surface of casein micelles liberates glycomacropeptide (GMP), and para -casein micelles aggregate to form a three-dimensional network. The effects of micellar size on the gelation were examined in the present work. Casein micelles with different sizes were prepared from skimmed milk by differential centrifugation. Micelle sizes were determined by turbidity measurements. The amount of GMP was estimated by high-performance liquid chromatography (HPLC). Complex rigidity G ∗ = G ′ + iG ″ was observed as a function of time after rennet was added to casein micelle solutions. Small micelles liberated more GMP per unit weight than large micelles. The growth of the storage modulus was well approximated by first order kinetics. The gel time for small micelles was shorter than that for large micelles, and was a decreasing function of temperature. The gelation rate constant K g was proportional to the concentration of rennet, and larger for small micelles. It is increased with increasing temperature. The final value of G ′ was proportional to the square of concentration, and showed a maximum at 27°C as a function of temperature. It is suggested that whilst hydrogen bonding is not negligible in the gelation of casein micelles, this event is governed mainly by hydrophobic interaction. Smaller micelles from a more solid-like gel than larger micelles.