Nobuki Murayama

Taste area in granular and dysgranular insular cortices in the rat identified by stimulation of the entire oral cavity

While applying natural stimulation to the entire oral cavity, we recorded responses from 489 neurons (400 mechanoreceptive, 84 taste and 5 cold neurons) in the insular cortex of urethane-anesthetized rats. Intermingled with the mechanoreceptive neurons was a major group of taste neurons located in the granular or dysgranular insular area at levels of 2.55-1.20 mm anterior to the bed nucleus of the anterior commissure as stereotaxically located. Most of the taste neurons were also sensitive to mechanical stimulation of the oral and/or perioral tissue.

Difference in taste quality coding between two cortical taste areas, granular and dysgranular insular areas, in rats

SummaryThe responses of 84 taste neurons to stimulation of the oral cavity in rats were examined; most taste neurons were found in either a granular insular area (area GI; n = 55) or dysgranular insular area (DI; n = 25), and the others (n = 4) were in an agranular insular area (area AI). The fraction of neurons responding to only one of the four basic stimuli was significantly larger in area GI than in area DI. When neurons were classified by the stimulus which most excited the neuron among the four basic stimuli, every “best-stimulus category” of neurons was found in both GI and DI areas. Quinine-best and “multistimulus-type” neurons, whose responses to some non-best stimulus exceeded 90% of the maximum, were more numerous in the cortex than in the thalamocortical relay neurons. When responses were plotted against taste stimuli arranged in the order of sucrose, NaCl, HCl, and quinine along the abscissa (taste coordinate), response profiles of taste neurons often showed two peaks. The double-peaked type of response profiles were found in every best-stimulus category of neurons in both areas; though, a significantly large fraction of quinine-best neurons in area GI were of the double-peaked type. Some taste neurons in area GI (n = 21) and in area DI (n = 7) were inhibited by one to two taste stimuli, particularly by the stimuli present next to the best one along the taste coordinate. In correlation profiles — correlation coefficients between sucrose and NaCl and between HCl and quinine — pairs of stimuli which were located next to each other on the taste coordinate were significantly smaller in area GI than in area DI. It is thus highly probable that area GI plays an important role in fine taste discrimination and area DI in integration of taste information.

Middle and long latency peak sources in auditory evoked magnetic fields for tone bursts in humans

The relative position of the P50m and the N100m sources of the auditory evoked magnetic field remains unclear. Magnetoencephalography was performed in 24 normal subjects. Contralateral P50m to left and right ear stimulus was observed in 21 and 19hemispheres, respectively. Ipsilateral P50m to left and right ear stimulus was observed in 17 and 16hemispheres, respectively. N100m was observed in all subjects for all stimuli. Relative position of the equivalent current dipole of the P50m was 1.0+/-7.6 (mean+/-SD) mm posterior, 2.0+/-5.8mm inferior and 1.8+/-8.0mm medial to the N100m dipole position considering all observations. We suggest that the P50m and N100m sources are colocated in an extended area of the cortex.

Gustatory evoked magnetic fields in humans

Magnetic fields evoked by taste stimuli of the human tongue were measured over the whole head using a helmet-shaped 64 channel magnetoencephalography system in five normal subjects. The stimuli were 10% glucose and 0.3 M NaCl solutions and distilled water. The most prominent peak (N175m) appearing over the bilateral hemispheres had a latency of 150-210 ms. The N175m sources were located using a two-dipole model in a spherical conducting medium based on the individual head dimensions and superimposed on magnetic resonance images. The N175m dipoles due to 10% glucose and 0.3 M NaCl stimuli were located at the operculum and circum-insular areas in both hemispheres, but those due to distilled water could not be located accurately.

Driver inattention monitoring system for intelligent vehicles: A review

This paper gives a review of the literature on driver inattention monitoring system for the purpose of active safe driving. In this paper driving inattention is classified into two categories: fatigue and distraction, while fatigue and distraction can also contain many types and levels. Individual difference on inattention phenomenon makes it more complicated to correctly detect and recognize driving inattention. Driver attention monitoring has been intensively researched in recent years and many approaches have been proposed, which include biological signal (EEG, ECG, EOG and sEMG) processing method, subjective report method, and behavior analysis method. This survey reviews a number of promising approaches and provides an overview of recent developments in this domain. The emphasis of this paper is to discuss the various methodologies to monitor driving inattention. We conclude with some thoughts about future directions.

Longitudinal changes of motor cortical excitability and transcallosal inhibition after subcortical stroke

Objective: To study serial changes in motor cortical excitability and transcallosal inhibition during post-acute and chronic phases up to one year after subcortical stroke. Methods: Single-pulse and paired-pulse trans cranial magnetic stimulation (TMS) were performed 3 times in 20 patients to obtain multiple measures, such as motor threshold, contralateral and ipsilateral silent periods, and short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). Twenty-one healthy subjects were also studied. Results: The results suggest that overall excitability on the unaffected motor cortex was increased and transcallosal inhibition from the unaffected to affected hemisphere was enhanced in the post-acute phase. These changes on the unaffected side returned to be normal following recovery rehabilitation. Conclusion: Excitability changes from the unaffected hemisphere are strongly associated with motor recovery. The results may help improve individualized rehabilitation strategies after stroke.

Difference in receptive field features of taste neurons in rat granular and dysgranular insular cortices

SummaryReceptive fields (RFs) of 59 cortical taste neurons (35 in the granular insular area, area GI, 21 in the dysgranular insular area, area DI, and 3 in the agranular insular area, area AI) were identified in the oral cavity of the rat. The fraction of the neurons with RFs in the anterior oral cavity only was significantly larger in area GI (74.3%) than in area DI (42.9%). On the other hand, the fraction of neurons with RFs in both the anterior and posterior oral cavity was larger in area DI (42.9%) than in area GI (11.4%). On the whole, it is suggested that area GI is involved in discrimination of several taste stimuli in the oral cavity, whereas in area DI taste information originating from various regions of the oral cavity is integrated. When neurons were classified according to the best stimulus which most excited the neuron among the four basic tastes, different categories of taste neurons had RFs in different parts of the oral cavity. It is suggested that, in either taste area, different categories of taste neurons are involved in different sorts of taste coding. The majority of neurons in both areas had bilateral RFs. In area GI, neurons with RFs on single subpopulations of taste buds were significantly more numerous at the rostral region of the cortex than at the caudal region. There was no such relation between RF types and cortical localization in area DI. Otherwise, topographic representation of the oral cavity by taste neurons on the cortical surface was not obvious. RF features of taste neurons did not differ across layers in either cortical area.

A Comparison of Urinary Albumin-Total Protein Ratio to Phase-Contrast Microscopic Examination of Urine Sediment for Differentiating Glomerular and Nonglomerular Bleeding

BACKGROUND Hematuria can be classified as either glomerular or nonglomerular, depending on the bleeding source. We recently reported that urinary albumin-total protein ratio is potentially useful for identifying the source of hematuria. STUDY DESIGN Diagnostic test study. SETTING & PARTICIPANTS 579 fresh urine specimens with microhematuria (> or =5 red blood cells/high-power field) collected from patients with the source of the hematuria confirmed on histopathologic and/or imaging studies and clinical criteria assessed. INDEX TEST Each urine specimen was evaluated morphologically by using phase-contrast microscopy and biochemically by using urinary albumin-total protein ratio, albumin-creatinine ratio, and total protein-creatinine ratio. REFERENCE TEST Each patient had a definitive clinical diagnosis established by means of biopsy (64.4%), imaging studies (21.2%), and routine optimal microscopic examination of urine sediment (14.3%). RESULTS Of 579 specimens, 329 were obtained from patients with glomerular disease and 250 were obtained from patients with nonglomerular disease. Mean urinary albumin-total protein, albumin-creatinine, and total protein-creatinine ratios for those with glomerular versus nonglomerular diseases were 0.73 +/- 0.11 versus 0.41 +/- 0.14 mg/mg (P < 0.001), 1,110 +/- 1,850 versus 220 +/- 560 mg/g (P < 0.001), and 1,600 +/- 3,010 versus 480 +/- 1,160 mg/g (P < 0.001), respectively. The percentage of patients with greater than 3% glomerular red cells was 83.3% versus 24.8% (P < 0.001). Receiver operating characteristic curve analysis showed that areas under the curve for albumin-total protein ratio, albumin-creatinine ratio, and total protein-creatinine ratio were 0.992, 0.781, and 0.688, respectively (P < 0.001, albumin-total protein versus albumin-creatinine; P < 0.001, albumin-total protein versus total protein-creatinine). At cutoff values of 0.59 mg/mg, 71 mg/g, and 265 mg/g, albumin-total protein ratio, albumin-creatinine ratio, and total protein-creatinine ratio had sensitivities and specificities of 97.3% and 100%, 78.9% and 61.1%, and 68.8% and 62.0% for detecting glomerular disease, respectively. Phase-contrast microscopy had sensitivity of 83.3% and specificity of 75.2% for detecting glomerular disease. LIMITATIONS Albumin-total protein ratio cannot be used in patients with urinary total protein less than 5 mg/dL (<0.05 g/L). Use of only 1 sample from 1 patient may not be sufficient to obtain definitive results. CONCLUSIONS Urinary albumin-total protein ratio is much more useful than phase-contrast microscopy for differentiating between glomerular and nonglomerular disease in patients with microscopic hematuria.

Parallel inhibition of cortico-muscular synchronization and cortico-spinal excitability by theta burst TMS in humans

OBJECTIVE To investigate the after-effects of theta burst TMS (TBS) on cortico-muscular synchronization, and on cortico-spinal excitability, in humans. METHODS We studied 10 healthy subjects using a continuous paradigm of TBS (cTBS), i.e. 600 pulses in 40s. Before and after the cTBS, coherence function was computed as a measure of cortico-muscular synchronization by recording electroencephalogram (EEG) from 19 scalp sites and electromyogram (EMG) from right first dorsal interosseous (FDI) muscle during the isometric contraction. In a separate experiment, motor-evoked potentials (MEPs) in response to single TMS pulses were recorded from the FDI muscle before and after the cTBS, to measure cortico-spinal excitability. RESULTS When the cTBS was applied over the left primary motor cortex (M1), the beta-band cortico-muscular coherence for the C3 scalp site, as well as the MEP amplitude significantly decreased in 30-60 min, and then recovered to the original levels in 90-120 min. Neither sham stimulation nor cTBS applied over 2 cm posterior to M1 produced significant effects. CONCLUSIONS cTBS-over-M1 can inhibit the cortico-muscular synchronization in parallel with the decline of cortico-spinal excitability. SIGNIFICANCE Our results provide the first evidence that TBS can efficiently alter the functional cortico-muscular coupling in humans.

Effects of concurrent visual tasks on cortico-muscular synchronization in humans

To study the effects of external visual stimulation on motor cortex-muscle synchronization, coherence between electroencephalography (EEG) and electromyography (EMG) was measured in normal subjects under Before, Task (visual task: Ignore or Count, or arithmetic task) and After conditions. The control (Before and After) conditions required the subject to maintain first dorsal interosseous muscle contraction without visual stimulation. In the visual task, a random series of visual stimuli were displayed on a screen while the subjects maintained the muscle contraction. The subjects were asked to ignore the stimuli in the Ignore condition and to count certain stimuli in the Count condition. Also, in the arithmetic task, the subjects were asked to perform a simple subtraction. The EEG-EMG coherence found at C(3) site at 13-30 Hz (beta) was increased and sustained in magnitude during the Ignore and Count conditions, respectively. To examine the cause of the change of coherence, changes of EEG and EMG spectral power were computed for each frequency band. There was little change in the EMG spectral power in any frequency bands. While the spectral power of EEG unchanged in the beta band, it significantly increased and decreased in the range of 8-12 Hz and of 31-50 Hz, respectively, for both Ignore and Count conditions, not only at the C(3) site but at various sites as well. These results were in contrast to those obtained for the arithmetic task: the beta band EEG-EMG coherence was attenuated and the EEG spectral power at 4-7 Hz and at 31-50 Hz were significantly increased and decreased, respectively. As a conclusion, the present results are consistent with the idea that the enhanced 8-12 Hz/decreased 31-50 Hz oscillations affect strength of the beta band cortico-muscular synchronization by suppressing the visual processing.