Abstract
- Top of page
- Abstract
- INTRODUCTION
- SUBJECTS AND METHODS
- RESULTS
- DISCUSSION
- ACKNOWLEDGMENTS
- REFERENCES
Abstract The objective of the present study was to evaluate the effect on the electroencephalogram (EEG) of a chewing gum with and without our prepared new flavor. Electroencephalograms were obtained after the following three tests: chewing pure gumbase with sucrose (standard gumbase), chewing flavored standard gum and the inhalation of flavored aromatic oil. As the control, we used the pre-stimulus control EEG record without a stimulus. We examined the relationship between the pre-stimulus control record and the post-stimulus record using the changes of power in four bands. Chewing the standard gumbase led to an increase in the alpha wave and a decrease in the beta wave. Chewing the flavored standard gum and inhaling the flavored aromatic oil each increased the alpha and beta waves. In addition, chewing the flavored standard gum led to a change in the ratio of theta wave in the frontal area. The difference in the theta, alpha and beta bands in chewing gum with and without the added flavor suggested that the flavor as well as chewing could induce concentration with a harmonious high arousal state in brain function.
INTRODUCTION
- Top of page
- Abstract
- INTRODUCTION
- SUBJECTS AND METHODS
- RESULTS
- DISCUSSION
- ACKNOWLEDGMENTS
- REFERENCES
It is generally thought that the act of mastication, even without calorie intake, has beneficial psychosomatic effects and increases brain function. Gum chewing is thought to alter brain function, mood, and to induce arousal. Mastication also reportedly improves learning ability,1 and increases the regional cerebral blood flow.2,3 Changes in the functional state of the brain have been detected in its electrical activity by means of global omega-complexity after the subjects chew gum.4 Self-rating results have demonstrated that subjects felt more refreshed and comfortable after chewing flavored gum than after chewing pure gumbase.5 It has been demonstrated in a self-reported psychological test that the arousal effect of gum chewing is a harmonious high arousal state in brain function (excellent and expedient).6 We recently reported a change in arousal observed on electroencephalogram (EEG) by chewing a marketed gum and the brain function with high efficiency, the so-called relaxed concentration, induced by chewing gumbase with added sucrose.7,8 However, the induction of arousal by chewing gum is still debated. Objective data are required to substantiate such claims of subtle subjective changes.
Our objective was to explain the effects of chewing gum with and without our prepared new flavor on the EEG of healthy subjects.
SUBJECTS AND METHODS
- Top of page
- Abstract
- INTRODUCTION
- SUBJECTS AND METHODS
- RESULTS
- DISCUSSION
- ACKNOWLEDGMENTS
- REFERENCES
Nine healthy Japanese adult volunteers, six men and three women, age range 27–33 years, gave informed consent for participation in the present study. The protocol was approved by the Institutional Review Committee of Kagoshima University Dental School. The study was conducted in accordance with the Helsinki Declaration of 1975 (1983 revision). No subject had a history of behavioral disturbance, abuse of drug or alcohol, diabetes, or other pre-existing medical condition. Their bodyweight, height, and build were all within the normal range. Six hours before the study they were forbidden to eat or drink any caffeine-containing beverages or alcohol, take drugs or medications, or use any form of tobacco.
The EEG was recorded before and after each of three stimuli with reference to linked ear electrodes from Fp1, Fp2, O1, O2, T3, T4, F3, F4, P3, P4, Fz, and Pz of the international 10–20 system (MME-3124; Nihon Kohden, Tokyo, Japan). The order of testing was as follows: (i) chew pure gumbase with sucrose but without flavored aromatic oil additives (standard gumbase); (ii) chew a standard gum with added flavored aromatic oil (flavored standard gum); and (iii) inhale the scent on a square of gauze (25 cm2) that had been soaked with flavored aromatic oil. Chewing was performed at a rate of approximately 70 times for 1 min. Tests of the three stimuli were separated by 7-day intervals. The composition of standard gumbase is polyvinyl acetate, natural resin, synthetic rubber, ester gum, natural wax, softener, calcium carbonate, and sucrose. Our prepared new flavored aromatic oil is shown in Table 1. Electroencephalogram recordings were obtained between 17:00 and 19:00 h with the subject resting quietly with eyes closed. Data were collected as follows: session I, 1 min at rest; session II, first 5 min recording (pre-stimulus control record); session III, each stimulus acting for 3 min; session IV, 1 min at rest; session V, 5 min recording (post-stimulus record). There was no interval between sessions.7,8 In the study by Masumoto et al. regarding this testing procedure, there was no significant difference in each wave (theta, alpha and beta) between the recordings in session II and session V (post-resting record) after resting instead of each stimulus in session IV.7 In addition, they also indicated the reproducibility in the recording method and the intra-individual reproducibility of EEG at the 7-day intervals. Therefore, arousal level in session II and session V was almost the same in the testing method.7 Artifacts were removed from the EEG by a 60 Hz notch filter at a sensitivity of 50 μV/mm. Electroencephalogram activity was filtered with 0.54 Hz highpass, 30 Hz lowpass filter. All data were carefully checked visually on the screen epoch-by-epoch for any artifacts caused by movement of the eyes or muscles. Any epochs that showed artifacts were eliminated from analyses.
Table 1. Constituent of flavored aromatic oil we prepared| Constituent of flavored aromatic oil | % |
|---|
| Peppermint | 6.5 |
| Lavender | 3.0 |
| Lemon balm | 0.3 |
| Chamomile | 0.1 |
| Lemon verbena | 0.1 |
| Middle Chain Tri-glyceride | 90.0 |
Electroencephalogram signals were recorded on a magnetic tape recorder (KS-616; Sony, Tokyo, Japan), and stored as digitized signals by an A/D converter at a 1 kHz sampling rate on the hard disk of a computer (PC9821-Xa13; Nihon Denki, Tokyo, Japan) for off-line analysis. We selected 180 s of artifact-free record in 300 s. Fast Fourier transformation (FFT) analysis was carried out for 1024 points with a Hanning window. We used the Finite Impulse Response (FIR) bank method to calculate the EEG power between 1.0 and 30.0 Hz in 1 Hz steps. The frequency components of the power spectrum were totaled into four frequency bands: delta, 1.0 under 3.0 Hz; theta, 3.0 under 8.0 Hz; alpha, 8.0 under 13.0 Hz; and beta, over 13.0 under 30.0 Hz. The subtle psychosomatic effects of each stimulus were evaluated in a combination of changes in these four bands on the EEG. The ratio of the frequency power of each band classified by the electrode position to the total frequency power of all electrode positions was determined.
We compared the differences between the prestimulus control record and each post-stimulus record by statistical testing. The comparison of map data with the ratio of the frequency power before and after stimulus in each band used the Significance Probability Mapping (SPM) process, which is based on the paired t-statistic.10,11 The established power was calculated by Coon's two-dimensional interpolation method for each frequency power band in two-dimensional plates projected according to the electrode placement.7 The SPM were color-coded and graded on an 8-point scale, with 1 (purple) representing the lowest P value and 8 (red) the highest. Purple (level 1 as the lowest probability) corresponded to P = 0.10, yellow (level 6) corresponded to P = 0.05, and red (level 8) corresponded to P = 0.001.
DISCUSSION
- Top of page
- Abstract
- INTRODUCTION
- SUBJECTS AND METHODS
- RESULTS
- DISCUSSION
- ACKNOWLEDGMENTS
- REFERENCES
Chewing the standard gumbase led to an increase in alpha waves and a decrease in beta waves. Chewing the flavored standard gumbase as well as inhaling the flavored aromatic oil led to an increase in the alpha and beta waves. The ratio of theta waves decreased after chewing the flavored standard gumbase. These results agree with those reported by Masumoto et al.8
Previous studies demonstrated an association between the alpha power and the psychosomatic state as reflected on the EEG.12–14 The changes in alpha power are related to the arousal level in the brain.15,16 The decrease in alpha power is closely related to attention, tension, and anxiety. Beta waves may be a useful measure of the cognitive and emotional processes.16 Therefore, the changes in EEG in the present study that were seen after chewing the standard gumbase suggested a lower arousal status in the brain and relaxation with respect to psychosomatic status as compared with pre-stimulus control EEG record. Chewing the flavored standard gumbase as well as inhaling the flavored aromatic oil suggested heightened arousal status as well as high cognitive and emotional status. However, there were differences in the theta and alpha wave ratios between chewing the flavored standard gumbase and inhaling the flavored aromatic oil. The theta waves after inhaling the flavored aromatic oil showed no significant change, while that observed after chewing the flavored standard gumbase showed a statistically significant decrease at eight positions. Furthermore, the significant changed positions in the alpha wave after inhaling the flavored aromatic oil decreased as compared with those observed after chewing the flavored standard gumbase. These differences may be related to chewing and also to the way of inhaling.17,18 However, we could not clearly explain these differences in the present study.
Buddhist monks with experience in Zen showed an increase in theta waves with a lessened degree of increase in slow alpha wave during meditation.19 The powers of the theta and the low frequency alpha bands were reported to be higher during pleasant than during unpleasant sounds.20 Thus, changes in theta and alpha waves also reflect the psychosomatic changes. The changes of theta wave after chewing the flavored standard gumbase were contradictory to the above reports that the changes on EEG in relaxation were described. However, the significant decrease in theta wave after chewing the flavored standard gumbase could be related to the high arousal level. Overall, the changes observed after inhaling the flavored aromatic oil could be suggested to reflect a higher arousal status, while the contradictory change among theta, alpha and beta that was observed after chewing the flavored standard gum may be interpreted as reflecting the harmonious status of arousal and relaxation, the so-called relaxed concentration.21
Gum chewing is not a simple voluntary act, but rather is a complex sequence of movements involving highly controlled brain functions.1,22 Gum chewing also involves several types of sensory stimulation such as the sense of smell, as well as taste and touch in the oral area.
While it has been demonstrated that chewing a pure gumbase induces changes in the EEG,4,8 the psychosomatic effect was inconclusive. In the study by Masumoto et al. the EEG changes recorded after chewing the pure gumbase showed a beta activity significantly increased in almost all the electrode positions, while the mean frequency on the alpha band was decreased.8 These changes did not clearly indicate either arousal or relaxation.8 No other reports are available on the effects of chewing the gumbase on EEG.
The sense of smell, which involves the stimulation of olfactory chemosensory receptor cells, can induce changes in the EEG and evoked potentials.23–25 Exposure of the subject to an odor is reliable in manipulating neurophysiological response systems; odor can affect the performance and mood of the human subject.26 Subliminal odors cause differing of the EEG characteristics among electrode positions (e.g. the scent of spiced apple produces more posterior beta than does the scent of lavender).25
Peppermint oil in combination with eucalyptus and ethanol was applied to large areas of the forehead and temples with a small sponge.17 The inhalation through the nose of peppermint oil increased cognitive performance and had a muscle and mentally relaxing effect in combination with eucalyptus oil and ethanol.17 Therefore, the scent of peppermint oil, which is the principal constituent within the flavored aromatic oil in the present study, may alter the EEG. Such changes may be also related to an inducing in cognitive brain function and in mental relaxation.
Lavender oil exhibits potent and reliable effects on the EEG.18 These effects are related to the duration of exposure.27 Interestingly, EEG alpha activity in the left hemisphere related to relaxation is reduced in those individuals who inhale through the nose rather than through the mouth.26 The psychophysiological effects of odor on the EEG resemble the effects of concentrated thought or a highly emotional state on the EEG,26 when the beta waves are dominant and the alpha waves are depressed. Therefore, the psychophysiological effects of the scent of lavender within the flavored aromatic oil in the present study may also be associated with an increase in cognitive brain function and mental relaxation. Actually, the significant position change after inhaling the flavored aromatic oil through the nose decreased in alpha wave compared with those after chewing the standard gumbase without the flavored aromatic oil. The decrease in alpha waves induced the relatively dominant beta wave. As a result, these changes could be related to the psychophysiological effects of odor indicated by Lorig et al.26 However, we could not clearly elucidate these differences in the present study.
Concerning the effect of sucrose in the standard gumbase, the ingestion of glucose causes greater EEG effects than does the ingestion of other carbohydrates.28 The absolute blood level of glucose is the primary determinant of the electrocortical changes observed mainly in the left parietal occipital and left temporal cortical region.28 A study that investigated effects for stress and relaxation induced by oral digestion of a complex-carbohydrates cereal, as evaluated by physiological and salivary measure, showed that chewing for the digestion of complex carbohydrates was more important to obtain deep relaxation.28,29 In the present study, the ingestion of sucrose in the standard gumbase had no significant effects on the EEG characteristics. The EEG was recorded only at 1 min after the ingestion of sucrose, which may not have been long enough for the blood glucose level to be affected. Therefore, the effect of the blood glucose level on the EEG could not be confirmed from the present results. However, the EEG changes in the present study also observed a greater left-sided activation after chewing the standard gumbase. These results in alpha wave after chewing the standard gumbase in the present study bore resemblance to a previous report that showed that the ingestion of sucrose produced a greater left-sided activation in both the frontal and parietal regions compared with water.30 Therefore, the present results suggested that the sucrose in standard gumbase may have been related to the taste of sucrose, not to the blood level of glucose.
The taste also has an important effect on the EEG. It has been reported that the degree of increase in alpha power depends upon the subjects' taste preference.31 A previous study has also shown that food images, especially the subject's favorite dessert, had a relaxant effect, as determined by EEG changes and self-reported assessment.32
We inferred from our comprehensive analysis of four bands on the EEG in chewing gum‚ with and without the added flavor, that chewing the flavored standard gum could induce concentration with a harmonious high arousal state in brain function. Although we could not be conclusive in our results, we believe that these changes depend on the combination of chewing, taste, smell, and food imagery. The observed effects on the EEG may also involve some direct chemical and/or pharmacological effects of the flavor that do not involve sensory perception.
We concede that further investigation needs to be undertaken to clarify the present inferences in the effects of chewing the flavored standard gum.
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