Sensory mismatch induces autonomic responses associated with hippocampal theta waves in rats.

Hippocampal (HIP) theta power increases during sensory mismatch, which has been suggested to induce motion sickness with autonomic abnormality (Zou et al., 2009 [29]). To investigate relationships between hippocampal theta rhythm and autonomic functions, theta waves in the HIP and electrocardiograms (ECGs) were recorded during sensory mismatch by backward translocation in awake rats. The rats were placed on a treadmill affixed to a motion stage that was translocated along a figure 8-shaped track. The rats were trained to run forward on the treadmill at the same speed as that of forward translocation of the motion stage (a forward condition) before the experimental (recording) sessions. In the experimental sessions, the rats were initially tested in the forward condition, and then tested in a backward (mismatch) condition, in which the motion stage was turned around by 180° before translocation. That is, the rats were moved backward by translocation of the stage although the rats ran forward on the treadmill. In this condition, proprioceptive information indicated forward movements while vestibular and visual information indicated backward movements. The theta (6-9 Hz) power was significantly increased in the backward condition compared with the forward condition. Spectral analysis of heart rate variability indicated that sympathetic nervous activity increased in the backward condition. These data (theta power and sympathetic nervous activity) were positively correlated. Furthermore, electrical stimulation of the HIP at theta rhythm (8 Hz) increased heart rate. These results suggest that sensory mismatch information activates the HIP to induce autonomic alteration in motion sickness.

Global synchronization in the theta band during mental imagery of navigation in humans.

Visual mental imagery is critical for successfully navigating the environment, which in turn activates many cortical regions simultaneously. Theta oscillation is implicated in navigation and brain synchronization. In this study, EEG coherence was analyzed during 3 tasks: subjects (1) mentally simulated jogging along the walls of a gym and pressed a button when they imagined arriving at a corner (jogging imagery task), (2) thought of and memorized one digit after pressing a button 5 times and recalled the digits sequentially after pressing the button again (digit imagery task), and (3) pressed a button (button pressing task). The results indicated that theta-wave (4-8 Hz) power was significantly higher in the frontal and parietal regions during the digit and jogging imagery tasks. Coherence at the theta band showed almost no differences between the button pressing and digit imagery tasks. Coherence between the distant regions, especially between the frontal and parieto-occipital regions and between interhemispheric regions, was significantly higher during the jogging imagery task. Increase in theta power during the jogging imagery task reflects working memory load to manipulate internal information. Theta oscillation appears to play an important role in large-scale synchronization to form the functional neuronal networks required for mental navigation.

Compression on trigger points in the leg muscle increases parasympathetic nervous activity based on heart rate variability.

Massotherapy, the therapeutic use of massage, is used to treat various chronic pain syndromes. One type of massotherapy, pressure stimulus applied over trigger points (TPs), is reported to have excellent therapeutic effects. Its effect is possibly mediated through changes in the autonomic nervous system although little research has been conducted to assess autonomic activity during TP compression. We have investigated how compression applied over TPs affects the autonomic nervous system. Six healthy young adult females whose daily working routine was carried out predominantly in a standing position were enrolled in the study cohort. After a day's work, the subjects were asked to rest supine, and electrocardiograms (ECGs), instantaneous lung volume (ILV) and systolic and diastolic blood pressures (SBP, DBP) were measured before and after pressure application over the TPs in those lower limb muscles where the subjects felt muscle fatigue or discomfort. The subjects were also asked to coordinate breathing with the beeping sounds. The therapeutic effects of TP compression were assessed by a subjective fatigue scale. Parasympathetic nervous activity was also assessed by spectral analysis of heart rate (HR) variability. The transfer function from ILV to HR was evaluated using linear analysis. The results indicated that TP compression (1) decreased HR, SBP and DBP, (2) increased parasympathetic activity, (3) increased the gain from ILV to HR, and (4) improved the fatigue scores. These findings suggest that an increase in parasympathetic nervous activity after the TP compression induced a reduction of fatigue. The therapeutic mechanisms of TP compression to enhance parasympathetic nervous system are discussed.

Effects of direct cedrol inhalation into the lower airway on autonomic nervous activity in totally laryngectomized subjects.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Relationships between smell sensation and autonomic changes have been studied extensively. However, the possibility that odorants may also act on the lung and lower airway remains unknown. WHAT THIS STUDY ADDS: The present results provide the first evidence that the lung and lower airway exert an inhibitory influence on the cardiovascular system in response to Cedrol (odorant) in the air under physiological conditions. AIMS: Previous studies reported that Cedrol (odorant) inhalation (CI) induced changes in autonomic balance and baroreceptor sensitivity (BRS) in both healthy subjects and anosmic patients. This suggests that Cedrol may act on the lower airway, and that the pulmonary system may exert an inhibitory influence on the cardiovascular system. METHOD: To test the above possibility, vaporized Cedrol (64.0 +/- 7.7 10(-9)m) or blank air was directly inhaled through the lower airway from a hole in the trachea, but not through the upper airway, using totally laryngectomized subjects. During the experiment, ECG, systolic (SBP) and diastolic (DBP) blood pressures were measured. Sympathetic and parasympathetic nervous activity was estimated by spectral analyses of variability in these parameters (heart rate variability (HRV), SBP variability (SBPV) and DBP variability (DBPV)). BRS was computed from transfer gain between SBP and the R-R interval of the ECG. RESULTS: SBP and DBP significantly decreased during CI, although there were no significant differences in HR and respiratory rate. BRS significantly increased during CI. The low frequency components of SBPV and DBPV (indices for sympathetic activity) significantly decreased during CI, while high frequency components of HRV (an index for parasympathetic activity) significantly increased. CONCLUSIONS: The present experiment using totally laryngectomized patients replicated the similar results in healthy subjects who inhaled Cedrol through the nose, suppression of sympathetic outflow and increase in parasympathetic outflow. These results demonstrated that Cedrol acts on the lower airway and pulmonary system, and suggest a new target for drug therapy of hypertension.

Specific acupuncture sensation correlates with EEGs and autonomic changes in human subjects.

Sympathetic overactivation is suggested to be associated with chronic pain syndrome, and acupuncture is frequently applied in therapy for this syndrome. Furthermore, the forebrain including the various cerebral cortices has been implicated in inhibitory and facilitatory control of pain as well as autonomic functions. We investigated relationships among specific sensations induced by acupuncture manipulation, effects on sympathetic and parasympathetic autonomic functions, and EEG changes. An acupuncture needle was inserted into the right trapezius muscle of the subjects, and acupuncture manipulation was repeated to induce specific acupuncture sensation repeatedly while the needle was left in the muscle. Acupuncture manipulation significantly decreased heart rate (HR), and increased systolic blood pressure (SBP). Spectral analysis indicated that acupuncture manipulation significantly decreased low frequency components (LF) of both HR variability (HRV) and SBP variability (SBPV), and significantly reduced ratio of LF to high frequency component (HF) of HRV (LF/HF, index of sympathetic activity). Furthermore, there was a significant negative correlation between changes in LF/HF ratio of HRV and the number of specific acupuncture sensations reported, and a significant positive correlation between HF of HRV and the number of acupuncture sensations. Analyses of EEG data indicated that acupuncture manipulation non-specifically increased power of all spectral bands except the gamma band. Furthermore, changes in HF (index of parasympathetic activity) and total power (overall activity of the autonomic nervous system) of HRV were positively correlated with changes in theta, alpha, and gamma power, while changes in LF of SBPV and LF/HF of HRV were negatively correlated with changes in power of all spectral bands. These results are consistent with the suggestion that autonomic changes induced by manipulation inducing specific acupuncture sensations might be mediated through the central nervous system, especially through the forebrain as shown in EEG changes, and are beneficial to relieve chronic pain by inhibiting sympathetic nervous activity.

Place-related neural responses in the monkey hippocampal formation in a virtual space.

Place cells in the rodent hippocampal formation (HF) are suggested to be the neural substrate for a spatial cognitive map. This specific spatial property of the place cells are regulated by both allothetic cues (i.e., intramaze local and distal cues) as well as idiothetic sensory inputs; the context signaled by the distal cues allows local and idiothetic cues to be employed for spatial tuning within the maze. To investigate the effects of distal cues on place-related activity of primate HF neurons, 228 neurons were recorded from the monkey HF during virtual navigation in a similar situation to a rodent water maze, in which distal cues were important to locate the animal's position. A subset of 72 neurons displayed place-related activity in one or more virtual spaces. Most place-related responses disappeared or changed their spatial tuning (i.e., remapping) when the arrangements of the distal cues were altered/moved in the virtual spaces. These specific features of the monkey HF might underlie neurophysiological bases of human episodic memory.

Neural correlates to action and rewards in the rat posterior cingulate cortex.

To investigate the involvement of the posterior cingulate cortex in reward-based learned actions, we examined its neuronal activities in rats that were trained in a delayed stimulus-response association task. Of the 344 neurons recorded, 178 responded during licking a spout to acquire rewards (a sucrose solution or intracranial self-stimulation). Of these 178 reward-responsive neurons, 80 responded exclusively during licking to acquire sucrose solution, and 20 during licking to acquire intracranial self-stimulation, with 37 of these 100 neurons displaying differential correlation to individual licking on the basis of the reward type. The present results and comparison with previous studies on the anterior cingulate cortex suggest that the posterior cingulate cortex is involved in the monitoring or storage of action-reward outcome association.

Effects of prenatal maternal stress by repeated cold environment on behavioral and emotional development in the rat offspring.

It has been reported that many types of stresses, which caused physiological and psychological alterations in dams as prenatal maternal stress, affected behavioral and emotional traits of their offspring. However, effects of environmental temperature changes, which induce various stress responses in both animals and humans, have not been assessed as prenatal maternal stress. Repeated cold stress (RCS) is a type of chronic cold stress in which environmental temperature changes rapidly and frequently several times within a day. In the present study, to investigate effects of chronic maternal stress by the RCS on behavioral and emotional development of the rat offspring (prenatal RCS rats), the RCS stress was loaded to pregnant rats between day 9 and 19 after fertilization. The prenatal RCS rats showed similar locomotor activity in an open field to control rats that were borne by non-stressed pregnant rats. On the other hand, the prenatal RCS rats showed significantly higher startle responses than the control rats in a light enhanced startle paradigm. However, treatment of diazepam decreased the startle responses in the prenatal RCS rats to the same degree as those in the control rats. The results indicated that prenatal RCS affected emotional development of the rat offspring, but not locomotor activity. Comparison of the present results with the previous studies suggests that there might be unknown common mechanisms among different prenatal maternal stresses that induce similar behavioral developmental alteration.

Effects of facial expression on shared attention mechanisms.

We investigated the effects of facial expression on shared attention mechanisms. A female or male facial stimulus with one of 3 facial expressions (happiness, neutral, or anger) was presented at the center of a display. This facial stimulus gazed toward a subject, or toward the left or right side of the display. After the facial stimulus was offset, a target appeared on the left or right side of the display and the reaction time to the target was measured. In the statistical analysis by ANOVA, there was a significant main effect of congruity between the target position and the gaze direction in both the female and male facial cues, indicating that gaze direction significantly affected reaction time. When the female facial cues were presented, the reaction times for the congruent target position to the gaze direction were significantly shorter in the happy than other facial expressions. However, there were no significant differences in reaction time when the facial stimuli were presented in an inverted orientation. The results demonstrated that facial expression significantly affected shared attention mechanisms.

Autonomic responses during inhalation of natural fragrance of Cedrol in humans.

It is well known that odors affect behaviors and autonomic functions. Previous studies reported that some compounds in cedar wood essence induced behavioral changes including sedative effects. In the present study, we analyzed cardiovascular and respiratory functions while subjects were inhaling fumes of pure compound (Cedrol) which was extracted from cedar wood oil. Vaporized Cedrol (14.2+/-1.7 microg/l, 5 l/min) and blank air (5 l/min) were presented to healthy human subjects (n=26) via a face mask, while ECGs, heart rate (HR), systolic blood pressure (SBP), diastolic BP (DBP), and respiratory rates (RR) were monitored. Statistical analyses indicated that exposure to Cedrol significantly decreased HR, SBP, and DBP compared to blank air while it increased baroreceptor sensitivity. Furthermore, respiratory rate was reduced during exposure to Cedrol. These results, along with the previous studies reporting close relationship between respiratory and cardiovascular functions, suggest that these changes in respiratory functions were consistent with above cardiovascular alterations. Spectral analysis of HR variability indicated an increase in high frequency (HF) component (index of parasympathetic activity), and a decrease in ratio of low frequency to high frequency components (LF/HF) (index of sympathovagal balance) during Cedrol inhalation. Furthermore, Cedrol inhalation significantly decreased LF components of both SBP and DBP variability, which reflected vasomotor sympathetic activity. Taken together, these patterns of changes in the autonomic parameters indicated that Cedrol inhalation induced an increase in parasympathetic activity and a reduction in sympathetic activity, consistent with the idea of a relaxant effect of Cedrol.

Gamma-band EEGs predict autonomic responses during mental arithmetic.

Relationship between gamma-band (20-80 Hz) EEGs and autonomic functions (heart rate, blood pressure, instantaneous lung flow) in a mental arithmetic task (MAT) were investigated. Subjects were instructed to add 2 integers after presentation of audio voices indicating the integers in the MAT, and to listen to the same voices without mental arithmetic in the control task. The gamma-EEGs and autonomic functions coherently changed in response to the voices before mental arithmetic in the MAT. Furthermore, an increase in gamma-EEGs went ahead of the autonomic fluctuation. The results suggest that the gamma-band activity modulates and adjusts peripheral autonomic functions in advance before actual mental activity. This is the first demonstration that cortical gamma-band activity triggers peripheral autonomic responses during mental activity.

Effects of aldehyde dehydrogenase-2 genotype on cardiovascular and endocrine responses to alcohol in young Japanese subjects.

The present study was designed to investigate the effects of aldehyde dehydrogenase-2 (ALDH2) genotype on cardiovascular and endocrine responses to alcohol ingestion in young, healthy Japanese subjects. For this purpose, we monitored changes in the electrocardiogram (ECG), blood pressure (BP), finger blood flow (BF) and facial skin temperature (FST) during and after alcohol ingestion (0.4 ml/kg body weight). Spectral analyses of beat-to-beat variations of heart rate (HR), BP and BF were applied. Two major spectral components were examined at low frequency (LF: 0.04-0.15 Hz) and high frequency (HF: 0.15-10.4 Hz) bands for HR and BP variability (BPV). Significant effects for ALDH2 genotype were observed in HR variability (HRV) analysis; HF power of HRV was markedly depressed and the LF/HF ratio was significantly higher with alcohol in ALDH2-deficient (ND) subjects, while ALDH2-normal (NN) subjects did not display such changes. Analysis of BP variability showed increased LF and HF power after alcohol ingestion in the NN subjects, but there were no significant differences between genotypic groups. We also examined BF variability (BFV) in six major spectral components; power of the 0.8-2.2 Hz frequency band was significantly affected by genotype and higher power was observed in the ND subjects. Plasma concentrations of both epinephrine and norepinephrine increased after alcohol ingestion only in the ND subjects. Furthermore, plasma concentrations and urinary excretion of epinephrine, but not norepinephrine, were higher after alcohol ingestion in the ND than in the NN subjects. Blood acetaldehyde levels were about 10-fold higher in the ND than in the NN subjects although blood alcohol levels similarly increased in the ND and NN subjects. Our results also indicated that alcohol ingestion increased secretion of pituitary-adrenal hormones including ACTH, beta-endorphin and cortisol in the ND subjects. The present results along with previous studies suggest that alcohol-induced tachycardia in the ND subjects was probably mediated by acetaldehyde-induced rise in epinephrine secretion from the adrenal medulla and/or changes in the autonomic nervous system. Alcohol-induced relative predominance of cardiac sympathetic activity in the ND subjects might be ascribed partly to increased norepinephrine secretion from sympathetic nerve terminals. Effects of acetaldehyde on these cardiovascular and endocrine systems were discussed in terms of their effects on the central nervous system.

Cardiac sympathetic denervation modulates the sympathoexcitatory response to acute myocardial ischemia.

OBJECTIVES: This study was designed to elucidate the influence of cardiac sympathetic denervation on the sympathoexcitatory response to acute myocardial ischemia during balloon coronary occlusion (BCO) in humans. BACKGROUND: Alterations of cardiac sympathetic nerve function could modulate sympathetic reflexes originating from the ischemic area. METHODS: In 23 patients with angina pectoris, we quantified the baseline cardiac sympathetic denervation of the ischemia-related area by iodine-123 metaiodobenzylguanidine ((123)I-MIBG), and transient changes in sympathetic activity during BCO by wavelet analysis of RR interval variability. RESULTS: Balloon coronary occlusion resulted in a transient augmentation of low-frequency (LF: 0.04 to 0.14 Hz) spectral components of RR interval variability in 4 of 12 patients with cardiac denervation and in 8 of 11 patients without denervation (p < 0.01 by the chi-square test). Consequently, the increase in LF components was significantly less during BCO in patients with cardiac denervation (34%) than in those without denervation (273%) (interaction: p < 0.05). In seven patients with severe ischemia provoked by a fall of > or = 10% in the left ventricular ejection fraction, LF components increased by 506% during BCO, regardless of the condition of cardiac denervation. In contrast, in patients with mild ischemia provoked by a fall of <10% in the ejection fraction, changes of LF components during BCO were significantly less in patients with denervation than in those without denervation (84 vs. 344%, p < 0.05). CONCLUSIONS: These findings suggest that if the provoked ischemia is not severe, cardiac sympathetic denervation could prevent ischemia-induced sympathoexcitation.