Adaptive brain activity changes during tongue movement with palatal coverage from fMRI data

Successful adaptation to wearing dentures with palatal coverage may be associated with cortical activity changes related to tongue motor control. The purpose was to investigate the brain activity changes during tongue movement in response to a new oral environment. Twenty-eight fully dentate subjects (mean age: 28.6-years-old) who had no experience with removable dentures wore experimental palatal plates for 7 days. We measured tongue motor dexterity, difficulty with tongue movement, and brain activity using functional magnetic resonance imaging during tongue movement at pre-insertion (Day 0), as well as immediately (Day 1), 3 days (Day 3), and 7 days (Day 7) post-insertion. Difficulty with tongue movement was significantly higher on Day 1 than on Days 0, 3, and 7. In the subtraction analysis of brain activity across each day, activations in the angular gyrus and right precuneus on Day 1 were significantly higher than on Day 7. Tongue motor impairment induced activation of the angular gyrus, which was associated with monitoring of the tongue's spatial information, as well as the activation of the precuneus, which was associated with constructing the tongue motor imagery. As the tongue regained the smoothness in its motor functions, the activation of the angular gyrus and precuneus decreased.

Cortical Regions Encoding Hardness Perception Modulated by Visual Information Identified by Functional Magnetic Resonance Imaging With Multivoxel Pattern Analysis

Recent studies have revealed that hardness perception is determined by visual information along with the haptic input. This study investigated the cortical regions involved in hardness perception modulated by visual information using functional magnetic resonance imaging (fMRI) and multivoxel pattern analysis (MVPA). Twenty-two healthy participants were enrolled. They were required to place their left and right hands at the front and back, respectively, of a mirror attached to a platform placed above them while lying in a magnetic resonance scanner. In conditions SFT, MED, and HRD, one of three polyurethane foam pads of varying hardness (soft, medium, and hard, respectively) was presented to the left hand in a given trial, while only the medium pad was presented to the right hand in all trials. MED was defined as the control condition, because the visual and haptic information was congruent. During the scan, the participants were required to push the pad with the both hands while observing the reflection of the left hand and estimate the hardness of the pad perceived by the right (hidden) hand based on magnitude estimation. Behavioral results showed that the perceived hardness was significantly biased toward softer or harder in >73% of the trials in conditions SFT and HRD; we designated these trials as visually modulated (SFTvm and HRDvm, respectively). The accuracy map was calculated individually for each of the pair-wise comparisons of (SFTvm vs. MED), (HRDvm vs. MED), and (SFTvm vs. HRDvm) by a searchlight MVPA, and the cortical regions encoding the perceived hardness with visual modulation were identified by conjunction of the three accuracy maps in group analysis. The cluster was observed in the right sensory motor cortex, left anterior intraparietal sulcus (aIPS), bilateral parietal operculum (PO), and occipito-temporal cortex (OTC). Together with previous findings on such cortical regions, we conclude that the visual information of finger movements processed in the OTC may be integrated with haptic input in the left aIPS, and the subjective hardness perceived by the right hand with visual modulation may be processed in the cortical network between the left PO and aIPS.

Effects of pseudoexperience on the understanding of hemiplegic movements in physical therapists: An fMRI study

Physical therapists (PTs) are required to obtain an accurate understanding of the physical and mental states of their patients through observational assessment. To perform comprehensive observational assessments of patients' movements, PTs likely need to engage their own neural systems involved in action understanding and theory of mind, such as the action observation network (AON) and the right temporoparietal junction (rTPJ). Both systems are modulated by the observer's actual experience with the observed movements. Although, most PTs do not have physical experience with neurological disabilities, they routinely examine hemiplegic movements in stroke patients, and are thus considered to have acquired pseudoexperience with hemiplegia. We hypothesized that the PTs' pseudoexperience with hemiplegia would modulate the neural system associated with the understanding of others to elaborately comprehend the physical and mental states associated with hemiplegia. To investigate our hypothesis, we recruited 19 PTs and 19 naïve participants (NPs) to undergo functional MRI (fMRI) for cortical activity measurement while viewing videos of hemiplegic (HHM) and non-hemiplegic (non-HHM) hand movements. The participants subsequently viewed the same videos again outside the MRI scanner, and evaluated the observed hand movements via a questionnaire. Compared to the NPs, the PTs showed greater activation in the AON and rTPJ while observing HHMs. Psychophysiological interaction analyses revealed increased connectivity between the rTPJ and AON when the PTs viewed the HHMs. Behavioral analyses further indicated that the PTs more accurately assessed feeling states associated with HHMs than did NPs. These findings suggest that the PTs' pseudoexperience modulates the AON and rTPJ, enabling them to better understand hemiplegia-associated feeling states.

Effects of storytelling on the childhood brain: near-infrared spectroscopic comparison with the effects of picture-book reading

In children, storytelling provides many psychological and educational benefits, such as enhanced imagination to help visualize spoken words, improved vocabulary, and more refined communication skills. However, the brain mechanisms underlying the effects of storytelling on children are not clear. In this study, the effects of storytelling on the brains of children were assessed by using near-infrared spectroscopy (NIRS). Results indicated significant decreases of the blood flow in the bilateral prefrontal areas during picture-book reading when the subjects were familiarized in comparison to the cases of the subject naïve to the stories. However, no significant differences in the blood flow were found during storytelling between the subjects naïve and familiarized to the stories. The results indicated more sustained brain activation to storytelling in comparison with picture-book reading, suggesting possible advantages of storytelling as a psychological and educational medium in children.

Effect of Visual Information on Active Touch During Mirror Visual Feedback

Several studies have demonstrated that observation of a dummy or mirror-reflected hand being stroked or moving at the same time as the hidden hand evokes a feeling that the dummy hand is one’s own, such as the rubber hand illusion (RHI) and mirror visual feedback (MVF). Under these conditions, participants also report sensing the tactile stimulation applied to the fake hands, suggesting that tactile perception is modulated by visual information during the RHI and MVF. Previous studies have utilized passive stimulation conditions; however, active touch is more common in real-world settings. Therefore, we investigated whether active touch is also modulated by visual information during an MVF scenario. Twenty-three participants (13 men and 10 women; mean age ± SD: 21.6 ± 2.0 years) were required to touch a polyurethane pad with both hands synchronously, and estimate the hardness of the pad while observing the mirror reflection. When participants observed the mirror reflection of the other hand pushing a softer or harder pad, perceived hardness estimates were significantly biased toward softer or harder, respectively, even though the physical hardness of the pad remained constant. Furthermore, perceived hardness exhibited a strong correlation with finger displacement of the mirrored, but not hidden, hand. The modulatory effects on perceived hardness diminished when participants touched the pad with both hands asynchronously or with their eyes closed. Moreover, participants experienced ownership of the mirrored hand when they touched the pad with both hands synchronously but not asynchronously. These results indicate that hardness estimates were modulated by observation of the mirrored hand during synchronous touch conditions. The present study demonstrates that, similar to passive touch, active touch is also modulated by visual input.

Prefrontal cortex activity during swallowing in dysphagia patients

Prefrontal cortex activity is modulated by flavor and taste stimuli and changes during swallowing. We hypothesized that changes in the modulation of prefrontal cortex activity by flavor and taste were associated with swallowing movement and evaluated brain activity during swallowing in patients with dysphagia. To evaluate prefrontal cortex activity in dysphagia patients during swallowing, change in oxidized hemoglobin (z-score) was measured with near-infrared spectroscopy while dysphagia patients and healthy controls swallowed sweetened/unsweetened and flavored/unflavored jelly. Total z-scores were positive during swallowing of flavored/unsweetened jelly and negative during swallowing of unflavored/sweetened jelly in controls but negative during swallowing of sweetened/unsweetened and flavored/unflavored jelly in dysphagia patients. These findings suggest that taste and flavor during food swallowing are associated with positive and negative z-scores, respectively. Change in negative and positive z-scores may be useful in evaluating brain activity of dysphagia patients during swallowing of sweetened and unsweetened food.

Effects of oral stimulation with capsaicin on salivary secretion and neural activities in the autonomic system and the brain

BACKGROUND/PURPOSE

Although it has been reported that capsaicin ingestion has effects of protecting stomach mucosa and promoting energy consumption, physiological responses to oral stimulation with capsaicin has not been elucidated. Therefore, we investigated the effect of oral capsaicin stimulation on oral health and mental conditions by measuring changes in salivation, autonomic nervous activity and electroencephalogram (EEG).

MATERIALS AND METHODS

Eighteen healthy adults participated in this study. The stimulus concentrations of capsaicin and five basic taste solutions were determined based on the measured threshold of each stimulus in each subject. The weight of secreted saliva and the changes in concentrations of salivary secretory immunoglobulin A (SIgA) induced by capsaicin and taste stimuli were measured. Salivary α-amylase activity and heart rate variability (HRV) were measured as indicators of autonomic nervous activity. From EEG, psychological condition was analyzed by measuring the powers of theta, alpha, and beta bands.

RESULTS

The salivary secretion rate was significantly increased by stimulation with capsaicin, NaCl, and citric acid compared with deionized water, and capsaicin demonstrated the most potent effect among tested stimuli. The secreted amount of SIgA per minute was elevated by capsaicin stimulation. Salivary α-amylase activity and HRV analysis demonstrated an elevation of sympathetic nervous activity induced by capsaicin. EEG analysis showed a significant increase in beta band power.

CONCLUSION

These results suggest that oral stimulation with capsaicin may be effective in improving oral conditions by increasing salivary flow and SIgA secretion, and in enhancing physical and mental conditions as indicated by sympathetic nerve and EEG changes.

Chewing Stimulation Reduces Appetite Ratings and Attentional Bias toward Visual Food Stimuli in Healthy-Weight Individuals

Based on the theory of incentive sensitization, the exposure to food stimuli sensitizes the brain’s reward circuits and enhances attentional bias toward food. Therefore, reducing attentional bias to food could possibly be beneficial in preventing impulsive eating. The importance of chewing has been increasingly implicated as one of the methods for reducing appetite, however, no studies to investigate the effect of chewing on attentional bias to food. In this study, we investigated whether chewing stimulation (i.e., chewing tasteless gum) reduces attentional bias to food as well as an actual feeding (i.e., ingesting a standardized meal) does. We measured reaction time, gaze direction and gaze duration to assess attentional bias toward food images in pairs of food and non-food images that were presented in a visual probe task (Experiment 1, n = 21) and/or eye-tracking task (Experiment 2, n = 20). We also measured appetite ratings using visual analog scale. In addition, we conducted a control study in which the same number of participants performed the identical tasks to Experiments 1 and 2, but the participants did not perform sham feeding with gum-chewing/actual feeding between tasks and they took a rest. Two-way ANOVA revealed that after actual feeding, subjective ratings of hunger, preoccupation with food, and desire to eat significantly decreased, whereas fullness significantly increased. Sham feeding showed the same trends, but to a lesser degree. Results of the visual probe task in Experiment 1 showed that both sham feeding and actual feeding reduced reaction time bias significantly. Eye-tracking data showed that both sham and actual feeding resulted in significant reduction in gaze direction bias, indexing initial attentional orientation. Gaze duration bias was unaffected. In both control experiments, one-way ANOVAs showed no significant differences between immediately before and after the resting state for any of the appetite ratings, reaction time bias, gaze direction bias, or gaze duration bias. In conclusion, chewing stimulation reduced subjective appetite and attentional bias to food, particularly initial attentional orientation to food. These findings suggest that chewing stimulation, even without taste, odor, or ingestion, may affect reward circuits and help prevent impulsive eating.

Effects of periodontal treatment on carotid intima-media thickness in patients with lifestyle-related diseases: Japanese prospective multicentre observational study

Atherosclerosis, a chronic inflammatory disease in arterial blood vessels, is one of the major causes of death in worldwide. Meanwhile, periodontal disease is a chronic inflammatory disease caused by infection with periodontal pathogens such as P. gingivalis (Porphyromonas gingivalis). Several studies have reported association between periodontal infection and atherosclerosis, but direct investigation about the effects of periodontal treatment on atherosclerosis has not been reported. We have planned Japanese local clinics to determine the relationship between periodontal disease and atherosclerosis under collaborative with medical and dental care. A prospective, multicentre, observational study was conducted including 38 medical patients with lifestyle-related diseases in the stable period under consultation at participating medical clinics and 92 periodontal patients not undergoing medical treatment but who were consulting at participating dental clinics. Systemic and periodontal examinations were performed before and after periodontal treatment. At baseline, LDL-C (low-density lipoprotein cholesterol) levels and percentage (%) of mobile teeth were positively related to plasma IgG (immunoglobulin) antibody titer against P. gingivalis with multivariate analysis. Corresponding to improvements in periodontal clinical parameters after treatment, right and left max IMT (maximum intima-media thickness) levels were decreased significantly after treatment (SPT-S: start of supportive periodontal therapy, SPT-1y: at 1 year under SPT, and SPT-3y: at 3 years under SPT). The present study has clarified our previous univariate analysis results, wherein P. gingivalis infection was positively associated with progression of atherosclerosis. Thus, routine screening using plasma IgG antibody titer against P. gingivalis and periodontal treatment under collaborative with medical and dental care may prevent cardiovascular accidents caused by atherosclerosis.

Visuomotor effects of body part movements presented in the first-person perspective on imitative behavior

Imitative stimuli presented from a first-person perspective (FPP) produce stronger visuomotor effects than those presented from a third-person perspective (TPP) due to the relatively greater response of the mirror neuron system (MNS) to FPP stimuli. Some previous studies utilizing TPP stimuli have reported no differences in MNS activity between moving and static bodies' stimuli. However, few studies have compared visuomotor effects of such stimuli when presented in the FPP. To clarify this issue, we measured cortical activation in 17 participants during a functional magnetic resonance imaging (MRI) imitation task involving three conditions: moving (a lifting finger was presented), static (an "X" appeared on a static finger), and control (an "X" appeared on a button). All stimuli were presented from the FPP or TPP. Participants were asked to lift the finger corresponding to the imitative stimulus. In the FPP condition, moving stimuli elicited greater MNS activation than static stimuli. Furthermore, such movement effects were stronger in the MNS and insula (a region associated with body-ownership) for FPP stimuli than for TPP stimuli. Psychophysiological interaction analysis revealed increased connectivity between the MNS and insula for moving stimuli in the FPP condition. These findings suggest that bodily movements presented in the FPP elicit a greater visuomotor response than static body presented in the FPP, and that the visuomotor effects of bodily movements were greater in the FPP condition than in the TPP condition. Our analyses further indicated that such responses are processed via the neural system underlying body-ownership. Hum Brain Mapp 38:6218-6229, 2017. © 2017 Wiley Periodicals, Inc.

Ventrolateral Prefrontal Cortex Updates Chosen Value According to Choice Set Size

Having chosen an item typically increases the subjective value of the chosen item, and people generally enjoy making choices from larger choice sets. However, having too many items to choose from can reduce the value of chosen items-for example, because of conflict or choice difficulty. In this study, we investigated the effects of choice set size on behavioral and neural value updating (revaluation) of the chosen item. In the scanner, participants selected items from choice sets of various sizes (one, two, four, or eight items). After they chose an item, participants rerated the chosen item, and we quantified revaluation by taking the difference of postchoice minus prechoice ratings. Revaluation of chosen items increased up to choice sets of four alternatives but then decreased again for items chosen from choice sets of eight alternatives, revealing both a linear and a quadratic effect of choice set size. At the time of postchoice rating, activation of the ventrolateral pFC (VLPFC) reflected the influence of choice set size on parametric revaluation, without significant relation to either prechoice or postchoice ratings tested separately. Additional analyses revealed relations of choice set size to anterior cingulate and insula activity during actual choice and increased coupling of both regions to revaluation-related VLPFC during postchoice rating. These data suggest that the VLPFC plays a central role in a network that relates choice set size to updating the value of chosen items and integrates choice overload with value-enhancing effects of larger choice sets.

<Original Article>Brain activity in patients with unilateral sensorineural hearing loss during auditory perception in noisy environments

Patients with unilateral sensorineural hearing loss (UHL) often complain of hearing difficulties in noisy environments. To clarify this, we compared brain activation in patients with UHL with that of healthy participants during speech perception in a noisy environment, using functional magnetic resonance imaging (fMRI). A pure tone of 1 kHz, or 14 monosyllabic speech sounds at 65‒70 dB accompanied by MRI scan noise at 75 dB, were presented to both ears for 1 second each and participants were instructed to press a button when they could hear the pure tone or speech sound. Based on the activation areas of healthy participants, the primary auditory cortex, the anterior auditory association areas, and the posterior auditory association areas were set as regions of interest (ROI). In each of these regions, we compared brain activity between healthy participants and patients with UHL. The results revealed that patients with right-side UHL showed different brain activity in the right posterior auditory area during perception of pure tones versus monosyllables. Clinically, left-side and right-side UHL are not presently differentiated and are similarly diagnosed and treated; however, the results of this study suggest that a lateralityspecific treatment should be chosen.

[Interface Between Brain and Outside]

Areas 5 and 7 are the association cortices which are located in the parietal lobe and process somatosensory and visual information, respectively. The location of area 7 differ in the Brodmann's human and monkey brain map, in the human brain map area 7 is located in the superior parietal lobe, while it is in the inferior parietal lobe in the monkey brain map. Thus, it is difficult to discuss the function of these areas.

Chewing-side Preference is Involved in Differential Cortical Activation Patterns during Tongue Movements after Bilateral Gum-chewing: a Functional Magnetic Resonance Imaging Study

Contralateral dominance in the activation of the primary sensorimotor cortex (S1/M1) during tongue movements (TMs) has been shown to be associated with a chewing-side preference (CSP). However, little is known about its interaction with chewing-related cortical activation. Functional magnetic resonance imaging was performed before and after gum-chewing in six subjects who exhibited a left CSP to determine the relationship between the CSP and activation patterns in the S1/M1 during TMs. Before the subjects chewed the gum, activation foci were found in the bilateral S1/M1. In the left hemisphere, both signal intensity and the area of activation significantly increased during TMs within 10 min after subjects chewed gum. Moreover, this augmented activation significantly decreased within 20 min during tongue protrusion and leftward movement. In the right hemisphere, there were no marked changes during TMs. These results suggest that bilateral gum-chewing enhances activation of the S1/M1 ipsilateral to the CSP during TMs.

Activation of the Human MT Complex by Motion in Depth Induced by a Moving Cast Shadow

A moving cast shadow is a powerful monocular depth cue for motion perception in depth. For example, when a cast shadow moves away from or toward an object in a two-dimensional plane, the object appears to move toward or away from the observer in depth, respectively, whereas the size and position of the object are constant. Although the cortical mechanisms underlying motion perception in depth by cast shadow are unknown, the human MT complex (hMT+) is likely involved in the process, as it is sensitive to motion in depth represented by binocular depth cues. In the present study, we examined this possibility by using a functional magnetic resonance imaging (fMRI) technique. First, we identified the cortical regions sensitive to the motion of a square in depth represented via binocular disparity. Consistent with previous studies, we observed significant activation in the bilateral hMT+, and defined functional regions of interest (ROIs) there. We then investigated the activity of the ROIs during observation of the following stimuli: 1) a central square that appeared to move back and forth via a moving cast shadow (mCS); 2) a segmented and scrambled cast shadow presented beside the square (sCS); and 3) no cast shadow (nCS). Participants perceived motion of the square in depth in the mCS condition only. The activity of the hMT+ was significantly higher in the mCS compared with the sCS and nCS conditions. Moreover, the hMT+ was activated equally in both hemispheres in the mCS condition, despite presentation of the cast shadow in the bottom-right quadrant of the stimulus. Perception of the square moving in depth across visual hemifields may be reflected in the bilateral activation of the hMT+. We concluded that the hMT+ is involved in motion perception in depth induced by moving cast shadow and by binocular disparity.

Analysis of resting salivation rate in patients with amyotrophic lateral sclerosis using tracheostomy invasive ventilation

Patients with amyotrophic lateral sclerosis (ALS) often suffer from salivation problems such as drooling and dry mouth. We examined resting salivation rate cross-sectionally in 66 advanced ALS patients with tracheostomy invasive ventilation using a cotton roll method, and investigated clinical factors associated with salivation rate. Resting salivation rate in the patients was well preserved (median value 0.6 g/min), and was significantly more increased in patients with impairment of jaw movement (P = 0.007) or mouth opening (P = 0.003) than in patients with less impairment, and in patients with the mouth being constantly open ≥ 10 mm in rostrocaudal length than in patients with < 10 mm. These data indicate that salivation rate was increased with progression of dysfunction of voluntary jaw movement. Appropriate oral care is required in advanced ALS patients to maintain their oral hygiene and to avoid penetration of saliva into the airway.

Spatial and Temporal Brain Responses to Noxious Heat Thermal Stimuli in Burning Mouth Syndrome

Burning mouth syndrome (BMS) is an idiopathic orofacial pain condition. Although the pathophysiology of BMS is not clearly understood, central and peripheral neuropathic mechanisms are thought to be involved. The authors compared brain response to noxious heat stimuli in 16 right-handed women with primary BMS and 15 sex- and age-matched right-handed healthy female controls. A thermal stimulus sequence of 32 °C to 40 °C to 32 °C to 49 °C was repeated 4 times in a cycle. Warm and noxious heat stimuli were delivered with a Peltier thermode placed on the right palm or right lower lip for 32 s each in a session. Functional magnetic resonance imaging data were obtained by recording echoplanar images with a block design. Statistical Parametric Mapping 8 software was used to analyze the data. Patients and controls both reported feeling more pain during palm stimulation than during lip stimulation. Repetition of noxious heat stimulus on the lower lip but not on the palm induced habituation in brain activity in the cingulate cortex without reduction in pain perception. Multiple regression analysis revealed a correlation between perceived pain intensity and suppression of brain activity in the anterior cingulate cortex when the repeated thermal sequence was applied at the lower lip. Furthermore, the response of the parahippocampal area differed in BMS patients and controls when the same repeated thermal sequence was applied at the palm. The authors’ findings indicate that BMS patients show specific brain responses due to impaired function of the central and peripheral nervous systems (clinical trial registration: UMIN000015002).

Macroglossia in advanced amyotrophic lateral sclerosis

INTRODUCTION

An enlarged tongue (macroglossia) has been reported in advanced-stage patients with amyotrophic lateral sclerosis (ALS).

METHODS

In this study we examined the prevalence of macroglossia and analyzed clinical correlations in 65 ALS patients on tracheostomy-invasive ventilation (TIV).

RESULTS

Macroglossia was found in 22 patients (33.8%). Compared with those without macroglossia, patients with macroglossia had a younger age of onset, longer duration of disease and TIV use, lower ALS Functional Rating Scale score, higher body mass index, lower energy intake, more severe communication impairment, and lower oral function. Logistic multivariate analysis showed that body mass index (BMI; P = 0.007) and communication impairment (P = 0.029) were significantly correlated with macroglossia. The duration of TIV use was at the cut-off level of significance (P = 0.05).

CONCLUSIONS

Macroglossia may be the result of overfeeding and replacement by fat during long-term TIV use in patients with advanced ALS. Muscle Nerve, 2016 Muscle Nerve 54: 386-390, 2016.

Depth perception from moving cast shadow in macaque monkey

In the present study, we investigate whether the macaque monkey can perceive motion in depth using a moving cast shadow. To accomplish this, we conducted two experiments. In the first experiment, an adult Japanese monkey was trained in a motion discrimination task in depth by binocular disparity. A square was presented on the display so that it appeared with a binocular disparity of 0.12 degrees (initial position), and moved toward (approaching) or away from (receding) the monkey for 1s. The monkey was trained to discriminate the approaching and receding motion of the square by GO/delayed GO-type responses. The monkey showed a significantly high accuracy rate in the task, and the performance was maintained when the position, color, and shape of the moving object were changed. In the next experiment, the change in the disparity was gradually decreased in the motion discrimination task. The results showed that the performance of the monkey declined as the distance of the approaching and receding motion of the square decreased from the initial position. However, when a moving cast shadow was added to the stimulus, the monkey responded to the motion in depth induced by the cast shadow in the same way as by binocular disparity; the reward was delivered randomly or given in all trials to prevent the learning of the 2D motion of the shadow in the frontal plane. These results suggest that the macaque monkey can perceive motion in depth using a moving cast shadow as well as using binocular disparity.

[Action]

In recent years, the mechanisms related to decision-making in the brain have been proposed and studied. The neural mechanisms involved in the selection of an action prior to its execution are becoming evident, particularly in relation to the frontal lobe. Nevertheless, the fundamental neural mechanisms of movement remain unknown, although it is generally accepted that these actions are controlled by higher-order motor areas in the brain. Movement is the result of a series of timed contractions of various muscle groups; however, elucidating the underlying neural basis of this temporal control would be a challenge in the future.

[Vision]

The existence of two visual information pathways has gained acceptance, and the entire scheme of visual information processing has been understood. The visual cortex has been subdivided into areas, whose neurophysiological properties have been examined in the monkey. Our understanding of the visual processing system has been built by information earned in parts. However, despite knowledge about the complete process, the associations between the individual components remain to be understood. In addition, elucidating the neural basis of perception experienced in daily living would be a challenge in the future.

Value of freedom to choose encoded by the human brain

Humans and animals value the opportunity to choose by preferring alternatives that offer more rather than fewer choices. This preference for choice may arise not only from an increased probability of obtaining preferred outcomes but also from the freedom it provides. We used human neuroimaging to investigate the neural basis of the preference for choice as well as for the items that could be chosen. In each trial, participants chose between two options, a monetary amount option and a "choice option." The latter consisted of a number that corresponded to the number of everyday items participants would subsequently be able to choose from. We found that the opportunity to choose from a larger number of items was equivalent to greater amounts of money, indicating that participants valued having more choice; moreover, participants varied in the degree to which they valued having the opportunity to choose, with some valuing it more than the increased probability of obtaining preferred items. Neural activations in the mid striatum increased with the value of the opportunity to choose. The same region also coded the value of the items. Conversely, activation in the dorsolateral striatum was not related to the value of the items but was elevated when participants were offered more choices, particularly in those participants who overvalued the opportunity to choose. These data suggest a functional dissociation of value representations within the striatum, with general representations in mid striatum and specific representations of the value of freedom provided by the opportunity to choose in dorsolateral striatum.

Standard electrocardiographic data of young Japanese monkeys (Macaca fusucata)

The electrocardiogram of nonhuman primates is similar to that of humans because of similar intrathoracic heart position and structure. Despite the frequent use of nonhuman primates in biologic studies, few electrocardiographic studies of Japanese monkeys (Macaca fusucata) have been reported, and no reference data are available for this species. We obtained limb-lead electrocardiograms from indoor-bred and housed ketamine-sedated Japanese macaques (48 male; 56 female; mean age, 44.3 mo; mean body weight, 4.84 kg) in the dorsal recumbency. The following quantitative data was obtained: heart rate, P wave amplitude and width, R wave amplitude, QRS duration, PR interval, QT interval, T wave height, and mean electrical axis. Corrected QT intervals were calculated by using the Bazett and Fridericia formulae. Measurements were evaluated according to sex and age. The duration of the QRS complex showed moderate correlation with age in male monkeys. All parameters, except heart rate, were similar to previous reports from Japanese, cynomolgus, and other macaques. P waves, R waves and mean electrical axis did not differ significantly between humans and Japanese macaques, but the wave amplitude in macaques was half that in humans. Our electrocardiographic measurements can serve as normal reference data for sedated, young Japanese monkeys.

Effect of transient vascular occlusion of the upper arm on motor evoked potentials during force exertion

We previously observed that transient vascular occlusion in volunteers increased the estimation of force exertion with no change in peripheral nerves or muscles. We hypothesized that the primary factor responsible for the overestimation of force exertion during occlusion was the centrally generated motor command, as hypothesized by McCloskey et al. (1974) and McCloskey (1978, 1981). In the present study, we tested the hypothesis that transient vascular occlusion increases the excitability of the primary motor cortex (M1) during force exertion. Healthy human volunteers lay on a bed and squeezed a dynamometer in their right hand. Repetitive gripping forces were exerted at 20%, 40%, or 60% of maximum force, with or without transient (20s) vascular occlusion of the proximal portion of the right upper arm. During the task, single-pulse transcranial magnetic stimulation was applied to the contralateral M1 to induce motor evoked potentials (MEPs) in the flexor carpi ulnaris (FCU) muscle. The MEP amplitudes were enhanced with occlusion under all conditions, with the exception of 60% contraction. In contrast, no significant difference was observed between the MEP amplitudes obtained from the occluded or non-occluded, relaxed FCU muscle. These results suggest that transient vascular occlusion increases the excitability of M1 only during force exertion.

Biochemical and hematologic effects of polyvinylpyrrolidone-wrapped fullerene C60 after oral administration

The fullerene C60 is used in consumer products such as cosmetics owing to its antioxidative effects and is being developed for nanomedical applications. However, knowledge regarding the safety of fullerene C60, especially after oral administration, is sparse. Here, we examined the safety of fullerene C60 in mice after 7 d of exposure to orally administered polyvinylpyrrolidone (PVP)-wrapped fullerene C60 (PVP-fullerene C60). Mice treated with PVP-fullerene C60 showed few changes in the plasma levels of various markers of kidney and liver injury and experienced no significant hematologic effects. Furthermore, the histology of the colon of PVP-fullerene C60-treated mice was indistinguishable from that of control mice. These results suggest that PVP-fullerene C60 lacks toxicity after high-dose oral administration and indicate that PVP-fullerene C60 can be considered safe for oral medication. These data provide basic information that likely will facilitate the production of safe and effective forms of fullerene C60.

Somatostatin-immunoreactive senile plaque-like structures in the frontal cortex and nucleus accumbens of aged tree shrews and Japanese macaques

BACKGROUND

Previously, we demonstrated decreased expression of somatostatin mRNA in aged macaque brain, particularly in the prefrontal cortex. To investigate whether or not this age-dependent decrease in mRNA is related to morphological changes, we analyzed somatostatin cells in the cerebra of aged Japanese macaques and compared them with those in rats and tree shrews, the latter of which are closely related to primates.

METHODS

Brains of aged macaques, tree shrews, and rats were investigated by immunohistochemistry with special emphasis on somatostatin.

RESULTS

We observed degenerating somatostatin-immunoreactive cells in the cortices of aged macaques and tree shrews. Somatostatin-immunoreactive senile plaque-like structures were found in areas 6 and 8 and in the nucleus accumbens of macaques, as well as in the nucleus accumbens and the cortex of aged tree shrews, where amyloid accumulations were observed.

CONCLUSIONS

Somatostatin degenerations may be related to amyloid accumulations and may play roles in impairments of cognitive functions during aging.

[Neural mechanisms for navigation]

To examine the neural basis of navigation we recorded the activity of neurons in the monkey medial parietal region (MPR) while monkeys actively navigated through a virtual environment. We found navigation neurons whose responses to the same movement at the same location were modulated depending on the route that the monkey was currently taking, that is, in a route-selective manner. The reversible inactivation of MPR neurons by muscimol resulted in a monkey becoming lost during the navigation task trial. These results suggest that MPR plays a critical role in navigation by integrating location information and self-movement information.

Gastric hypomotility in chronic upper gastrointestinal disease of Japanese macaques (Macaca fuscata)

Japanese macaques bred indoor for laboratory use often show chronic anorexia and intermittent vomiting. In some of our macaques gastric air was observed on physical examination, and we suspected abnormality of gastric motility. We therefore performed contrast radiographic examinations of the gastrointestinal tract without anesthesia of 8 macaques with gastrointestinal symptoms and 9 asymptomatic controls from the same laboratory. Changes of abdominal radiography over time were observed following oral administration of contrast medium. In all control animals, contrast medium had completely passed from the stomach within 150 min after administration. However, all animals with gastrointestinal symptoms retained some contrast medium in the stomach. Gastric emptying time of contrast medium was associated with excessive gastric air in Japanese macaques; therefore, gastric emptying time seems to be associated with decreased gastric motility.

Amyloid beta (Aβ) protein- and amyloid precursor protein (APP)-immunoreactive structures in the brains of aged tree shrews

BACKGROUND

Amyloid beta (Aβ) accumulates in the human brain in an age-dependent manner during normal aging. However, Aβ accumulation has not been observed in rodents during normal aging. Tree shrews, the experimental animals studied here, are as small as rats but have a longer life span than rodents.

METHODS

We investigated Aβ accumulations in the brains of young and aged tree shrews by amyloid histochemistry and immunohistochemistry using antibodies to Aβ-42, Aβ-40, Aβ-16 and amyloid precursor protein (APP).

RESULTS

In the brain of young tree shrews, there were no Aβ- immunoreactive (-ir) and APP-ir profiles. In the brains of aged tree shrews, Aβ-42-ir neuronal profiles were observed in the cortex, subiculum, basal ganglia, mammillary body and hypothalamus, but there were only a few weak Congo red-positive amyloid deposits. Aβ-42-, Aβ-40-, Aβ-16- and APP-ir blood vessels were observed.

CONCLUSIONS

An early stage of amyloid accumulation occurs in the brains of aged tree shrews, indicating that this animal may be a good model for studying the start of Aβ accumulation.

Perception of object motion in three-dimensional space induced by cast shadows

Cast shadows can be salient depth cues in three-dimensional (3D) vision. Using a motion illusion in which a ball is perceived to roll in depth on the bottom or to flow in the front plane depending on the slope of the trajectory of its cast shadow, we investigated cortical mechanisms underlying 3D vision based on cast shadows using fMRI techniques. When modified versions of the original illusion, in which the slope of the shadow trajectory (shadow slope) was changed in 5 steps from the same one as the ball trajectory to the horizontal, were presented to participants, their perceived ball trajectory shifted gradually from rolling on the bottom to floating in the front plane as the change of the shadow slope. This observation suggests that the perception of the ball trajectory in this illusion is strongly affected by the motion of the cast shadow. In the fMRI study, cortical activity during observation of the movies of the illusion was investigated. We found that the bilateral posterior-occipital sulcus (POS) and right ventral precuneus showed activation related to the perception of the ball trajectory induced by the cast shadows in the illusion. Of these areas, it was suggested that the right POS may be involved in the inferring of the ball trajectory by the given spatial relation between the ball and the shadow. Our present results suggest that the posterior portion of the medial parietal cortex may be involved in 3D vision by cast shadows.

Establishment of vertebral heart scale in the growth period of the Japanese macaque (Macaca fuscata)

We performed a thoracic X-ray examination of 56 Japanese macaques to obtain normal reference values for vertebral heart scale (VHS). Mean VHS was 10.25 +/- 0.94 v. In males, mean VHS was 10.56 +/- 0.73 v, with no significant correlation to age or weight. In contrast, mean VHS in females was 9.97 +/- 1.03 v, and tended to decrease with increasing age and weight. These findings will facilitate the diagnosis of cardiac disease in Japanese macaques in the future.

Cortical areas related to performance of WAIS Digit Symbol Test: a functional imaging study

Many neuropsychological studies have shown that the Digit Symbol Test (DST) of the Wechsler Adult Intelligence Scale (WAIS) is useful for screening for dysfunctions of the brain. However, it remains unclear which brain areas are actually involved in the performance of DST and what brain functions are used for executing this test. In this study, we examined the cortical areas related to cognitive aspects of DST using functional magnetic resonance imaging (fMRI) and determined executive brain functions involved in this test on the basis of fMRI results. Eleven healthy young adults (mean=21.6 years) performed a modified DST (mDST) task and its control task, which required a simple graphomotor response during fMRI data acquisition. The direct comparison of brain activations between the mDST task and the control task revealed greater activations in a fronto-parietal cortical network, including the bilateral inferior frontal sulci, left middle frontal gyrus (close to the frontal eye field) and left posterior parietal cortex. These activations are interpreted as reflecting the visual search process and/or the updating process of working memory during the mDST task execution. Furthermore, we found a positive correlation between the number of correct responses and activations in the bilateral inferior frontal regions, suggesting that these prefrontal areas have a crucial role in the performance of DST in a healthy young adult population.

Context-dependent place-selective responses of the neurons in the medial parietal region of macaque monkeys

To investigate the role of the medial parietal region (MPR), comprising area 7 m and the retrosplenial and posterior cingulate cortices, in spatial navigation, we analyzed the spatial aspect of the responses of the MPR neurons in monkeys while they actively performed a navigation task in a virtual environment. One-third of the analyzed MPR neurons were activated depending on the location of the monkeys in the environment, that is, showed place-selective responses. Some neurons showed varying responses based on the starting point (SP) or destination. We further investigated the responses of the place-selective neurons when the monkeys were shown animations of the entire navigation route, including the preferred field, and a segment of the route, including an area around the preferred field, and a still image of the preferred field. We observed that the responses of some place-selective neurons reduced when the monkeys viewed the preferred field in the segmented animation or in the still image compared with when they viewed the entire animation. These results suggested that the knowledge about the SP or destination, that is, context, is necessary to activate place-selective neurons. The effect of such contextual information suggests that the MPR plays decisive roles in spatial processing such as navigation.

Random number generation evaluation in patients with systemic lupus erythematosus indicates a heterogeneous nature of central nervous system vulnerability

OBJECTIVE

To evaluate the vulnerability of the central nervous system (CNS) in patients with systemic lupus erythematosus (SLE).

METHODS

Forty-eight patients with SLE, 58 with schizophrenia in remission and 39 healthy controls were enrolled in the study. Patients vocally generated 100 numbers in a random fashion, using numbers 0 to 9, and were evaluated with seriality scores. Patients with SLE were subgrouped according to differences in the presence of Raynaud's phenomenon, anti-phospholipid antibody, lupus activity, and a history of neuropsychiatric (NP) lupus, and these patients were also evaluated by comparison with their counterparts.

RESULTS

In general, patients with SLE showed lower seriality scores than patients with schizophrenia, and higher seriality scores than normal controls. The scores of the patients with a history of NP lupus matched those with schizophrenia, and the scores of never having NP lupus matched those of the healthy controls.

CONCLUSIONS

CNS vulnerability may be prolonged in patients who have a history of NP lupus even when they appear to be in normal NP status. The damage in random number generation (RNG) observed in patients with a history of NP lupus seemed equal to that found in those with schizophrenia, whereas those patients never having NP lupus appeared to be equal to the controls. The current study suggests a heterogeneous nature of SLE and prolonged damage, especially in CNS vulnerability, when evaluating with RNG.

Relating neuronal firing patterns to functional differentiation of cerebral cortex

It has been empirically established that the cerebral cortical areas defined by Brodmann one hundred years ago solely on the basis of cellular organization are closely correlated to their function, such as sensation, association, and motion. Cytoarchitectonically distinct cortical areas have different densities and types of neurons. Thus, signaling patterns may also vary among cytoarchitectonically unique cortical areas. To examine how neuronal signaling patterns are related to innate cortical functions, we detected intrinsic features of cortical firing by devising a metric that efficiently isolates non-Poisson irregular characteristics, independent of spike rate fluctuations that are caused extrinsically by ever-changing behavioral conditions. Using the new metric, we analyzed spike trains from over 1,000 neurons in 15 cortical areas sampled by eight independent neurophysiological laboratories. Analysis of firing-pattern dissimilarities across cortical areas revealed a gradient of firing regularity that corresponded closely to the functional category of the cortical area; neuronal spiking patterns are regular in motor areas, random in the visual areas, and bursty in the prefrontal area. Thus, signaling patterns may play an important role in function-specific cerebral cortical computation.

Neurons, or nerve cells in the brain, communicate with each other using stereotyped electric pulses, called spikes. It is believed that neurons convey information mainly through the frequency of the transmitted spikes, called the firing rate. In addition, neurons may communicate some information through the finer temporal patterns of the spikes. Neuronal firing patterns may depend on cellular organization, which varies among the regions of the brain, according to the roles they play, such as sensation, association, and motion. In order to examine the relationship among signals, structure, and function, we devised a metric to detect firing irregularity intrinsic and specific to individual neurons and analyzed spike sequences from over 1,000 neurons in 15 different cortical areas. Here we report two results of this study. First, we found that neurons exhibit stable firing patterns that can be characterized as “regular”, “random”, and “bursty”. Second, we observed a strong correlation between the type of signaling pattern exhibited by neurons in a given area and the function of that area. This suggests that, in addition to reflecting the cellular organization of the brain, neuronal signaling patterns may also play a role in specific types of neuronal computations.