Tatsu Kobayakawa

Enhancement of Sweetness Ratings of Aspartame by a Vanilla Odor Presented Either by Orthonasal or Retronasal Routes

When taste stimuli are presented with specific odor stimuli, the perceived intensity of taste is enhanced, a phenomenon called odor-induced taste enhancement. There is a possibility, however, that the odor substances might have stimulated the taste receptors in the oral cavity as well as odor receptors in the nasal cavity because the odor substances were dissolved in the taste solutions in some preceding studies. Schifferstein and Verlegh (1996) found that the odor-induced taste enhancement effect was not found when the subjects wore a nose clip to prevent the olfactory perception. Thus, it was suggested that the odor-induced taste enhancement did not result from the stimulation of receptors in the oral cavity. To confirm and extend their study, we presented the odor stimuli simultaneously with, but not dissolved in, the taste stimuli with a more advanced approach to stimulus presentation. The participants reported enhancement of sweetness ratings for aspartame when the taste stimuli were presented with a vanilla odor. This odor-induced taste enhancement was found when the gaseous odor stimuli were presented either by the retronasal route or by the orthonasal route. There was little possibility that the vanilla odor stimulated the taste receptors during the orthonasal stimulation because the odor stimuli were presented directly into the nasal cavity. Thus, we could show that the odor-induced taste enhancement is elicited by olfactory perception. These results also suggested that there is little functional difference between retronasal and orthonasal olfaction.

Cardiac sympathetic degeneration correlates with olfactory function in Parkinson's disease.

Autonomic and olfactory dysfunctions are considered markers for preclinical diagnosis in Parkinsons disease (PD), because pathological changes in these systems can start before motor symptoms develop. We investigated whether cardiac sympathetic function and olfactory function are associated in PD. Participants comprised 40 nondemented patients with idiopathic PD, and age‐matched controls. Cardiac sympathetic function was evaluated by 123 I‐metaiodobenzylguanidine (MIBG) uptake, in terms of the heart to mediastinum (H/M) ratio in both early and delayed images, and the washout rate (WR). Olfactory function was evaluated using the Odor Stick Identification Test for Japanese, which evaluates the detection of 12 odorants familiar to Japanese participants. Smell identification scores were significantly lower (P < 0.001) in patients with PD than in controls. Smell identification scores correlated positively with early (P < 0.05) and delayed H/M ratios (P < 0.01), and inversely with the WR (P < 0.005) especially in patients with early PD (below 5 years of the start of motor symptoms), whereas smell identification scores did not correlate with any parameters of MIBG in the advanced PD (above 5 years of the start of motor symptoms). There was no correlation between motor symptom scores and smell identification scores, H/M ratios, or WR. The results suggest that the cardiac sympathetic nervous system might degenerate in parallel with the olfactory system in patients with early PD, and that these two systems might degenerate at a different rate of speed in advanced PD.

Differences in odor identification among clinical subtypes of Parkinson's disease.

Objective:u2002 Olfactory dysfunction is a non‐motor symptom in idiopathic Parkinson’s disease (PD). We investigated whether this dysfunction differs among clinical subtypes of PD.

Effects of intermittent odours on cognitive-motor performance and brain functioning during mental fatigue

Effects of intermittent presentation of odours on cognitive-motor performance and brain activity during mental fatigue were examined using event-related brain potentials. Participants performed a Go/NoGo task for 60 min, in both odour and air control conditions. The time-on-task reaction time increase was significantly smaller in the odour condition than in the air control condition. Go- and NoGo-P3 amplitudes were larger in the presence of odours than during the air control, during mental fatigue. There were no effects of odours on error negativity (Ne)/error-related negativity (ERN) amplitude and latency. These results suggest that the presence of intermittent odours improves attentional/effortful control of response selection, and that this effect mitigates the deterioration of cognitive-motor performance during mental fatigue. Practitioner Summary: The present study provides evidence for a potentially effective strategy, the use of odours, to mitigate deficits in cognitive-motor performance during time-on-task. The results show that the presence of intermittent odours is an efficient tool for maintenance of attention and reaction time during a prolonged task.

Evaluation of card-type odor identification test for Japanese patients with olfactory disturbance.

Objectives: A card-type odor identification test, Open Essence (OE), was recently developed in order to examine olfactory function in the Japanese population. The purpose of this study was to validate the efficacy of this new test by comparison with established olfactory examinations. Methods: We administered Jet Stream Olfactometry (JSO), an intravenous olfaction test (Alinamin test), a visual analog scale of symptoms of olfactory dysfunction, and the OE test to 50 patients with complaints of olfactory disturbance and 50 healthy volunteers. After comparison of the OE test results with those of existing olfactory examinations and the symptom scores, we tried to estimate a cutoff value compatible with the JSO threshold. Results: The scores on the OE test showed significant correlations with the average detection thresholds of JSO (r = −0.738; p < 0.0001), the average recognition thresholds of JSO (r = −0.708; p < 0.0001), the symptom scores (r = 0.827; p < 0.0001), and the duration scores of the intravenous olfactory test (r = 0.673; p < 0.0001). The area under the receiver operating characteristics curve between the OE test results and the average recognition thresholds of JSO was highest when the OE tests cutoff value was set at 8. Conclusions: The OE test proved to be a useful tool for screening olfactory disturbance in the Japanese population. Scores of 8 or higher on the OE test should be judged as normal for screening.

High-speed gas sensor for chemosensory event-related potentials or magnetic fields

The observation of odor and air exchange with high temporal accuracy is necessary to obtain strict chemosensory event-related potentials (CSERPs) or magnetic fields, as proposed by Evans et al. [Evans W, Kobal G, Lorig T, Prah J. Suggestions for collection and reporting of chemosensory (olfactory) event-related potentials. Chem Senses, 1993; 18: 751- 6]. No suitable method for real time observation of gas stimuli, however, has been available until now. We have developed a technique to measure accurately gas molecule concentrations with a high temporal resolution. We determined that attenuation of sound amplitude varies in a manner dependent on the average molecular weight through which the sound wave passes. Based on this principle, we have designed a high-speed gas concentration sensor utilizing ultrasound. We investigated the practical potential of this sensor using a chemosensory stimulator (olfactometer); we succeeded in observing rapid gas exchange between air and nitrogen with a 2 kHz sampling rate. The signal/noise ratio of the stimulus was greater than 42 dB. In a 20 min experiment we determined that, for this olfactometer, the gas onset latency was 79 ms and the rise time was 16 ms. No significant artifact to magnetic fields was observed, even when the sensor was situated near a whole head magnetoencephalography (MEG) system. These results indicate that this sensor could be used for the observation of odor and air exchange, as well as, for real time monitoring of odor stimuli during actual experiments with a participant.

Temporal Characteristics of Neural Activity Associated with Perception of Gustatory Stimulus Intensity in Humans

We previously reported that cortical activities of the transition between the parietal operculum and the insula (area G) showed to increase in a concentration-dependent manner using stimuli containing 30xa0mM to 1xa0M NaCl. We investigated, in this study, the relationship between the magnitude of the activity with the shortest latency and the perceived gustatory stimulus intensity. We also examined the latencies at which activities correlated significantly with neural processes encoding perceived intensity and estimated the locations of the cortical areas associated with these latencies.

Construction of a measurement system for simultaneity judgment using odor and taste stimuli

BACKGROUNDnThe modalities examined in previous simultaneity judgment (SJ) were limited to vision, audition, and touch. By contrast, olfaction and gustation have not been addressed to date in SJ.nnnNEW METHODnIn this study, we constructed a measurement system for performing SJ with three cross-modal, combinations of odor, taste, and light stimuli. Odor and taste stimulators were able to stimulate to only the receptors corresponding to the modalities of each stimulus, without inducing tactile sensation. Furthermore, in order to precisely calculate the time points at which stimulus reached receptors in each trial, we monitored the presented stimuli in real time. After we calculated the actual values of stimulus onset asynchrony (SOA) between standard and comparison stimuli on the basis of the records of real-time monitoring, we evaluated the temporal distributions of simultaneous response rates in each cross-modal combination.nnnRESULTSnWhen we fitted a Gaussian distribution to these temporal distributions, we observed low error rates in all cross-modal combinations, as demonstrated in SJ using visual, audio, and tactile stimuli.nnnCOMPARISON WITH EXISTING METHOD(S)nSJ using chemical stimuli and SJ using physical stimuli exhibit the same degree of measurement accuracy.nnnCONCLUSIONSnWe succeeded in development a high accurate measurement system for SJ using chemical stimuli. We attribute this success to the use of strict real-time monitoring of stimulus presentation.

Clinical application of a card-type odor identification test to olfactory assessment in Parkinson's disease

OBJECTIVESnCurrent studies have provided valuable evidence that Parkinsons disease (PD) is closely associated with olfactory loss and that the use of olfactory testing is regarded as one of the potential screening tools for early diagnosis of PD.nnnMETHODSnTwenty-six patients with PD, age- and sex-matched 14 patients with other neurological diseases and 10 healthy controls were evaluated the sense of smell by the Open Essence (OE).nnnRESULTSnThe motor performance of the patients with PD was assessed using the Hoehn and Yahr scale. The OE scores for patients with PD were significantly lower than those with both the patients with other neurological diseases and controls. There was no significant difference of the OE scores between patients with other neurological diseases and controls. In the PD group, the OE score was not correlated with gender, smoking habit, disease duration, age at examination, or cognitive status. However, the OE scores were significantly correlated with Hoehn and Yahr stages.nnnCONCLUSIONnOE was found to be practically self-administered, time-saving, reliable, and inexpensive method for correct diagnosis of olfactory dysfunction associated with PD.

A high-concentration NaCl solution does not stimulate the human trigeminal nerve at the tip of the tongue.

Conclusion. A 3 M NaCl solution does not stimulate the trigeminal nerve in the human tongue. Objectives. In rats, the trigeminal nerve has been reported to respond when the tongue is stimulated by a solution with an NaCl concentration of 0.4 M or greater. We have attempted to clarify whether or not relatively high concentrations of NaCl stimulate the trigeminal nerves of the human tongue. Materials and methods. We examined four patients whose bilateral chorda tympani nerves were resected during middle ear surgeries. We performed subjective tactile and taste tests. Next, we conducted objective examinations of the subjects’ tactile and gustatory functions by magnetoencephalography (MEG). Results. The subjective examination confirmed that all four subjects maintained normal tactile sensory functions in their tongues and that the gustatory sensation at their lingual apexes was totally abolished. Furthermore, the objective examination of the tactile function using MEG indicated that their brain responses to trigeminal nerve stimulations were normal. Further examination using MEG failed to produce brain responses to a 3 M NaCl solution in spite of their normally functioning trigeminal nerves. Therefore, we concluded that a 3 M NaCl solution does not stimulate the trigeminal nerve at the tip of the human tongue.