Saho Ayabe-Kanamura

The primary gustatory area in human cerebral cortex studied by magnetoencephalography

Magnetic fields (MFs) from gustatory stimulation with 1 M NaCl and 3 mM saccharin were recorded from the human brain by using a whole-cortex SQUID system. The averaged onset latency of MFs was 93 ms for NaCl and 172 ms for saccharin and no response was obtained for water. A high correlation coefficient was noted between the difference of onset MFs latencies in two tastants and that of behavioral reaction times, and responses to saccharin were delayed or abolished after treatment of a subjects tongue with a sweet-suppressing agent. This finding indicates that the MFs obtained were caused by gustatory stimulation. By plotting the estimated current dipole on the magnetic resonance image, we could locate the primary gustatory area at the transition area between the operculum and insula, as reported in macaque monkeys.

EFFECT OF VERBAL CUES ON RECOGNITION MEMORY AND PLEASANTNESS EVALUATION OF UNFAMILIAR ODORS

The experiment investigated the effect of verbal cues on recognition memory for unfamiliar odors. 58 participants learned 20 odors of chemical substances. The control group learned the odors without accompanying verbal labels whereas two other groups learned the odors with accompanying verbal labels. The labels referred to relatively pleasant or unpleasant odor sources. On a memory test, administered 15 min. and also 1 wk. after the learning phase, participants were asked to recognize 10 learned odors from 10 unlearned odors and to evaluate each odors pleasantness. Analysis showed (a) the verbal labels did not facilitate recognition of the unfamiliar odors, (b) recognition performance was lower after 1 wk. than after 15 min., and (c) rated pleasantness tended to be affected by the verbal label assigned to the odor in the learning phase.

Are Olfactory Images Sensory in Nature

We investigated the features of olfactory mental images by comparing odour images with perceptual and semantic representations. Participants who were assigned to three groups made similarity judgments about 17 common odours by smelling odours, imagining odours, or on the basis of the meaning of odour source names. In the smelling group, every pair of odours was compared. In the imagining group, imagined odours were compared twice, both before and after associative learning of the odour/name combinations. In the meaning group, the odour source names were compared in terms of general word meanings. Nonmetric multidimensional scaling analysis was applied to each group of similarity data and three-dimensional sensory, mental, and semantic spaces were composed. 17 elements in the mental and semantic spaces were super-imposed onto the sensory space by Procrustes rotation. We found that the averaged distances of the 17 elements between the sensory and the mental spaces (either before or after learning) were smaller than those between the sensory and semantic spaces. We suggest that odour images have sensory features, especially after associative learning between perceived odours and their names.

Smell Behavior During Odor Preference Decision

The present study investigated the orienting behaviors in perception of odors during a preference-based decision-making task. The focus of our study was on smell duration, especially during the first exposure. Participants were instructed to choose the most preferred odor among multiple alternatives. The alternatives in experiments 1, 2, and 3 were manipulated so that the similarity among alternatives became higher; in experiment 1, the alternatives were chosen from multiple categories (e.g., laundry detergents and beverages); in experiment 2, they were from a single category (six kinds of flavored tea); and in experiment 3, they were from a single subcategory (six kinds of jasmine tea). Results showed that the chosen odor was smelled longer than nonchosen odors (the smell bias effect) during the first exposure. However, this effect only occurred when alternatives consisted of different categories. Furthermore, the smell bias effect did not occur when participants chose the most intense odor. These results suggest that orienting behavior reflected participants’ preference only when the odors were relatively easy to discriminate from each other.

The Influence of Olfactory Contexts on the Sequential Rating of Odor Pleasantness

When we sequentially evaluate the characteristics of sensory stimuli, our evaluation of a current stimulus is influenced by those preceding it. One such effect is called hedonic contrast, whereby stimuli are rated more negatively (negative contrast) or positively (positive contrast) if they are preceded by more or less pleasant stimuli. The present study investigated the characteristics of hedonic contrast for olfaction and compared these characteristics with those of a more oft-studied modality, vision. The results from two experiments indicated that both positive and negative contrasts occurred in the sequential rating of picture pleasantness, whereas only negative contrast occurred for olfactory ratings. Notably, overrating of hedonically negative odors following a positive olfactory context was observed even when participants had already rated these same negative odors beforehand; conversely, this did not occur for positive contrast for either sense. These findings indicate that negative odors are more strongly influenced than positive ones, and the rating of positive stimuli may be adjusted to the preceding rating independent of stimulus context. The findings of this study revealed the unique characteristics of hedonic contrast for the olfactory senses.

Characteristics of Haptic Peripersonal Spatial Representation of Object Relations

Haptic perception of space is known to show characteristics that are different to actual space. The current study extends on this line of research, investigating whether systematic deviations are also observed in the formation of haptic spatial representations of object-to-object relations. We conducted a haptic spatial reproduction task analogous to the parallelity task with spatial layouts. Three magnets were positioned to form corners of an isosceles triangle and the task of the participant was to reproduce the right angle corner. Weobserved systematic deviations in the reproduction of the right angle triangle. The systematic deviations were not observed when the task was conducted on the mid-sagittal plane. Furthermore, the magnitude of the deviation was decreased when non-informative vision was introduced. These results suggest that there is a deformation in spatial representation of object-to-object relations formed using haptics. However, as no systematic deviation was observed when the task was conducted on the mid-saggital plane, we suggest that the perception of object-to-object relations use a different egocentric reference frame to the perception of orientation.

Changes in Detection Thresholds of Androstenol and Pentalide During the Menstrual Cycle

Fluctuations in women’s sensory sensitivity, feelings, and behavior during the menstrual cycle have been suggested. Most studies of olfactory sensitivity have suggested increased sensitivity during the ovulatory phase [1,2,3]. However, several reports have noted a secondary peak during the luteal phase [1] and some have reported no changes during the menstrual cycle [3]. The physiological mechanisms for these responses related to each phase are not fully understood. Some authors have suggested that changes in olfactory sensitivity might be due to peripheral mechanisms that limit the access of odorant molecules to olfactory receptors [2], while others have indicated that these changes might be directly related to the central nervous system, which is affected by sexual hormones [3]. The possible involvement of human pheromones is very interesting. Androstenol and androstenone, which have musk-like odors, occur both in urine and as a product of the apocrine glands in humans and are secreted more by men than by women. Although these pheromones are implicated in the sexual behavior of the boar, their effects on humans are not well known. Some studies [3] have suggested that there is no relationship between the menstrual cycle and olfactory sensitivity for non-human odors, but that sensitivity does change for particular human odors, such as that of androstenone.

Position of the egocenter in the perception of peri-personal space using haptics

Spatial representations of peri-personal space formed from haptics are known to show non-veridical characteristics, which have been suggested to be the result of the egocentric reference frame. The current study investigated the position of the egocenter when perceiving space through haptics in order to understand how positions in space are encoded and whether there are positions in space that are easily perceived with arm movements. Understanding of human characteristics in the perception of space using haptics will shed light into user friendly designs of interfaces which are manipulated using the hands.

Measurement of Gustatory-Evoked Magnetic Fields with Sharp Stimulation

Non-invasive methods to measure brain function, particularly the methods of magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI), have improved rapidly and remarkably. With these methods, researchers have measured higher cortical functions of the living human brain, especially visual and auditory functions. MEG has the special advantage that it can trace the movement of cortical activity.

The Relation Between Gustatory-Evoked Magnetic Fields and Reaction Times to Different Taste Qualities

Kobayakawa et al. reported the development of a new gustatory stimulation apparatus for which the rise-time was less than 20 ms for a measurement of EEG [1]. They also modified the apparatus for a measurement of MEG, and reported the estimation of the source of the gustatory-evoked magnetic fields (GEMs) in the human cerebral cortex [2] [3]. In the present study we measured the reaction times (RTs) to the different taste qualities and compared them with the GEMs of different taste qualities to find the mutual relation between the reaction times and the onset of GEMs.