Biomedical subjects

Haruka Dan

Publications and source records attributed to Haruka Dan.

11 recordsLinked to original sources

PubMed2006

Interactive relationship between the mechanical properties of food and the human response during the first bite.

Biting is an action that results from interplay between food properties and the masticatory system. The mechanical factors of food that cause biting adaptation and the recursive effects of modified biting on the mechanical phenomena of food are largely unknown. We examined the complex interaction between the bite system and the mechanical properties. Nine subjects were each given a cheese sample and instructed to bite it once with their molar teeth. An intra-oral bite force-time profile was measured using a tactile pressure-measurement system with a sheet sensor inserted between the molars. Time, force, and impulse for the first peak were specified as intra-oral parameters of the sample fracture. Mechanical properties of the samples were also examined using a universal testing machine at various test speeds. Besides fracture parameters, initial slope was also determined as a mechanical property possibly sensed shortly after bite onset. The bite profile was then examined based on the mechanical parameters. Sample-specific bite velocities were identified as characteristic responses of a human bite. A negative correlation was found between bite velocity and initial slope of the sample, suggesting that the initial slope is the mechanical factor that modifies the consequent bite velocity. The sample-specific bite velocity had recursive effects on the following fracture event, such that a slow velocity induced a low bite force and high impulse for the intra-oral fracture event. We demonstrated that examination of the physiological and mechanical factors during the first bite can provide valuable information about the food-oral interaction.

Adaptation, Physiological↗

PubMed2006

Prefrontal activity during flavor difference test: application of functional near-infrared spectroscopy to sensory evaluation studies.

Sensory evaluation (SE) of food attributes involves various levels of cognitive functions, yet not much has been studied about its neural basis. Using multi-channel functional near-infrared spectroscopy (fNIRS), we examined the activation of the anterior portion of the lateral prefrontal cortex (LPFC) of 12 healthy volunteers during the SE of tea samples. The experimental task used corresponded to the early phase of the same-different test, and required subjects to attentively taste tea samples and memorize their flavors. To isolate activation associated with the cognitive functions involved in the task, we contrasted the results with those achieved by a control (Ctl) task during which subjects held familiar tea samples in their mouths without actively evaluating their flavor. We probabilistically registered the fNIRS data to the Montreal Neurological Institute standard brain space to examine the results as they correspond with other published neuroimaging studies. We found significant activation in the left LPFC and in the right inferior frontal gyrus. The activation pattern was consistent with earlier studies on encoding of other sensory stimuli, with cortical regions supposed to be involved in semantic and perceptual processing. This research makes a start on characterizing the cognitive process employed during SE from the neuroimaging perspective.

Adult↗

PubMed2006

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 LPFC's 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.

Adult↗

PubMed2005

Spatial registration of multichannel multi-subject fNIRS data to MNI space without MRI.

The registration of functional brain data to the common brain space offers great advantages for inter-modal data integration and sharing. However, this is difficult to achieve in functional near-infrared spectroscopy (fNIRS) because fNIRS data are primary obtained from the head surface and lack structural information of the measured brain. Therefore, in our previous articles, we presented a method for probabilistic registration of fNIRS data to the standard Montreal Neurological Institute (MNI) template through international 10-20 system without using the subject's magnetic resonance image (MRI). In the current study, we demonstrate our method with a new statistical model to facilitate group studies and provide information on different components of variability. We adopt an analysis similar to the single-factor one-way classification analysis of variance based on random effects model to examine the variability involved in our improvised method of probabilistic registration of fNIRS data. We tested this method by registering head surface data of twelve subjects to seventeen reference MRI data sets and found that the standard deviation in probabilistic registration thus performed for given head surface points is approximately within the range of 4.7 to 7.0 mm. This means that, if the spatial registration error is within an acceptable tolerance limit, it is possible to perform multi-subject fNIRS analysis to make inference at the population level and to provide information on positional variability in the population, even when subjects' MRIs are not available. In essence, the current method enables the multi-subject fNIRS data to be presented in the MNI space with clear description of associated positional variability. Such data presentation on a common platform, will not only strengthen the validity of the population analysis of fNIRS studies, but will also facilitate both intra- and inter-modal data sharing among the neuroimaging community.

Adult↗

PubMed2004

Measurement of bite force variables related to human discrimination of left-right hardness differences of silicone rubber samples placed between the incisors.

This study was designed to examine human subjects' ability to discriminate between spatially different bite pressures. We measured actual bite pressure distribution when subjects simultaneously bit two silicone rubber samples with different hardnesses using their right and left incisors. They were instructed to compare the hardness of these two rubber samples and indicate which was harder (right or left). The correct-answer rates were statistically significant at P < 0.05 for all pairs of different right and left silicone rubber hardnesses. Simultaneous bite measurements using a multiple-point sheet sensor demonstrated that the bite force, active pressure and maximum pressure point were greater for the harder silicone rubber sample. The difference between the left and right was statistically significant (P < 0.05) for all pairs with different silicone rubber hardnesses. We demonstrated for the first time that subjects could perceive and discriminate between spatially different bite pressures during a single bite with incisors. Differences of the bite force, pressure and the maximum pressure point between the right and left silicone samples should be sensory cues for spatial hardness discrimination.

Adult↗

PubMed2004

Transient exposure to ethylene stimulates cell division and alters the fate and polarity of hypocotyl epidermal cells.

After transient exposure to the gaseous hormone ethylene, dark-grown cucumber (Cucumis sativus) hypocotyls developed unusual features. Upon ethylene's removal, the developing epidermis showed significant increases in cell division rates, producing an abundance of guard cells and trichomes. These responses to ethylene depended on the stage of development at the time of ethylene exposure. In the upper region of the hypocotyl, where cells were least differentiated at the onset of ethylene treatment, complex, multicellular protuberances formed. Further down the hypocotyl, where stomata and trichomes were beginning to develop at the onset of ethylene exposure, an increase in the number of stomata and trichomes was observed. Stomatal complexes developing after the ethylene treatment had a significant increase in the number of stomatal subsidiary cells and the number of cells per trichome increased. Analysis of division patterns in stomatal complexes indicated that exposure to ethylene either suspended or altered cell fate. Ethylene also altered cell division polarity, resulting in aberrant stomatal complexes and branched trichomes. To our knowledge, the results of this study demonstrate for the first time that transient treatment with physiological concentrations of ethylene can alter cell fate and increase the propensity of cells to divide.

Cell Differentiation↗

PubMed2004

Effects of sample hardness on human chewing force: a model study using silicone rubber.

This study aims to clarify the effects of sample hardness on chewing force of humans. Silicone rubber was chosen as a food model, and three silicone rubber samples of varying hardness were chewed between the upper and lower incisors or molars in a natural way. Chewing force, contact area between a specimen and teeth, and pressure applied into the specimen were dynamically measured with a multiple-point sheet sensor. The multiple-point measurement revealed that a harder sample evoked higher peak force, longer duration, higher impulse, and higher active pressure values, whereas the chewing cycle and time to peak were not affected by sample hardness. The contact area between the sample and teeth decreased for the harder sample during incisor chewing. The peak force and force-related parameters, contact area, time to peak and bite force duration showed higher values for molar bites than for incisor bites, while the chewing cycle was similar in both cases. The measurement with the sheet sensor system clearly indicated that sample hardness modified chewing force of humans. We hypothesise that the effect of sample hardness is mainly mediated by mechanoreceptors in the periodontal ligament.

Adult↗

PubMed2004

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.

Adult↗

PubMed2004

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.

Activities of Daily Living↗

PubMed2003

Ethylene stimulates endoreduplication but inhibits cytokinesis in cucumber hypocotyl epidermis.

The effects of ethylene on cell division are generally considered inhibitory. In this study, we demonstrate that transient ethylene exposure, while suppressing cytokinesis, stimulates DNA synthesis. We monitored DNA synthesis and cytokinesis in the epidermis of cucumber (Cucumis sativus) hypocotyls, an organ whose post-germination development involves strictly limited cell division. During exposure to ethylene, DNA synthesis, assessed by the incorporation of the thymidine homolog 5-bromo-2'-deoxyuridine, was detected in 20% of the epidermal cells, whereas DNA synthesis was nearly undetectable in normal air. Cytofluorometric analysis of nuclei in affected cells showed an up to 8-fold increase in DNA content. During this time, new cell plate formation was not detected. However, shortly after ethylene was removed, DNA content was rapidly restored to 2C (diploid) levels in all cells, and new cell plate formation dramatically increased. These results demonstrate that ethylene promotes DNA synthesis and its endoreduplication but inhibits cytokinesis, thereby maintaining some cells in G2 phase.

Cell Division↗

PubMed2003

Active stress during compression testing of various foods measured using a multiple-point sheet sensor.

Using a multiple-point sheet sensor (MSS), load and contact area were directly measured for compression of four different foods. The MSS provided temporal and spatial changes in stress applied on the sample surface during the testing. The sum of load value detected by the MSS corresponded to the load measured by a universal testing machine during the compression. The contact area between a flat probe and food surface varied with the variety of foods even though under a small strain, and increased as compression strain increased. The active stress, that is, the load divided by the contact area, was different from conventional stress, that is, the load divided by the initial cross-sectional area. The value of active stress provided a better explanation of textural characteristics of food, because texture is often sensed under a large deformation and mixed assessment of mechanical and geometrical properties.

Agar↗