Lateralized ultradian rhythms of the right and left brain: temporal variations of tactile discrimination tested in German subjects.

Endogenous ultradian rhythms with a periodicity of 2-3 hours operate separately in the right and left hemispheres of the human brain and modulate physiological functions, perception and cognition. Since sensory pathways from either hand terminate in the contralateral hemisphere, ultradian rhythms of the right and left brain can be monitored by variations in the tactile discrimination of the left and right hand, respectively. Thirteen right-handed German males were tested every 15 minutes for 8 hours. Time series of the tactile error rate determined for the right and left hands oscillate with significantly different ultradian periodicities. Whereas cycles in tactile discrimination of the right hand (left hemisphere) have a periodicity of about 2 hours, tactile discrimination of the left hand (right hemisphere) is modulated by longer periods of about 3 hours. This is interpreted in terms of the overall functional asymmetry of the human brain. Since the left brain is the specialized locus for verbal processing and the right brain for visual-spatial processing, lateralized ultradian rhythms operating in the hemispheres may provide a distinct frame for long-term timing of neuronal processes underlying semantic and spatial mapping of the environment. This is particularly important for interpreting biosocial behavioural rhythms seen in humans living under natural conditions.     

Ultradian and Asymmetric Rhythms of Hemispheric Processing Speed

Daily changes in cognitive performance have been documented, both in time of day/effect paradigm studies and in time‐isolation studies. However, in both types of studies, phenomena such as the “post‐lunch dip” have been found that were difficult to explain in terms of theoretical backgrounds. These phenomena may suggest ultradian rhythms in cognitive performance. A number of studies have also shown ultradian and asymmetric rhythms in activity indices of the brain hemispheres. The aim of this study was to test three hypotheses: the first two assumed that there is a significant ultradian frequency in a component of the endogenous rhythm of processing speed, and the third assumed that the ultradian endogenous rhythms of the processing speed (encoding and recognition) of stimuli addressed to the left brain hemisphere differ in period length from those addressed to right hemisphere. During a 24 h constant‐routine experiment, the memory performance of 30 participants was measured eight times (every 2.5–3 h), starting at 06:30 h. Parallel sets of words and pictures were shown to subjects in a random order in either the left or the right visual field on a computer screen. The participants pressed one of two buttons in response to the picture or word, or when answering a question concerning the meaning of a presented stimulus. Cosinor analysis was applied to individual time series data. Two significant ultradian components were found in a majority of the time series. Dominant periods were analyzed using three factor ANOVA. The results showed an asymmetry between both hemispheres in the frequency of ultradian rhythms in encoding speed.     

Ultradian and asymmetric rhythms of hemispheric processing speed

Daily changes in cognitive performance have been documented, both in time of day/effect paradigm studies and in time-isolation studies. However, in both types of studies, phenomena such as the “post-lunch dip” have been found that were difficult to explain in terms of theoretical backgrounds. These phenomena may suggest ultradian rhythms in cognitive performance. A number of studies have also shown ultradian and asymmetric rhythms in activity indices of the brain hemispheres. The aim of this study was to test three hypotheses: the first two assumed that there is a significant ultradian frequency in a component of the endogenous rhythm of processing speed, and the third assumed that the ultradian endogenous rhythms of the processing speed (encoding and recognition) of stimuli addressed to the left brain hemisphere differ in period length from those addressed to right hemisphere. During a 24 h constant-routine experiment, the memory performance of 30 participants was measured eight times (every 2.5-3 h), starting at 06:30 h. Parallel sets of words and pictures were shown to subjects in a random order in either the left or the right visual field on a computer screen. The participants pressed one of two buttons in response to the picture or word, or when answering a question concerning the meaning of a presented stimulus. Cosinor analysis was applied to individual time series data. Two significant ultradian components were found in a majority of the time series. Dominant periods were analyzed using three factor ANOVA. The results showed an asymmetry between both hemispheres in the frequency of ultradian rhythms in encoding speed.     

Ultradian rhythms in processing speed of laterally exposed words and pictures

The study was designed to find out the cerebral hemispheres oscillations in stimuli processing during the 24-hour period of wakefulness in isolated subjects remaining in a monotonous environment. Stimuli processing speed from the 24-hour constant routine periods (06.00-06.00 h) of a larger experiment were analysed for the purpose of this paper. Parallel sets of words and pictures were exposed laterally using a purpose-designed computer program. The subjects reacted to pictures or words by pressing appropriate buttons. The significant dominant ultradian rhythms (around 4 h) in the processing speed of words addressed to the right hemisphere were found and of pictures addressed to the left hemisphere. Longer significant dominant periodicities (around 12 h) appeared in the processing speed of words addressed to the left hemisphere and of pictures (around 8 h) addressed to the right hemisphere. Ultradian rhythmicity of the central nervous system functioning is suggested.     

Sustained Spatial Attention to Vibrotactile Stimulation in the Flutter Range: Relevant Brain Regions and Their Interaction

The present functional magnetic resonance imaging (fMRI) study was designed to get a better understanding of the brain regions involved in sustained spatial attention to tactile events and to ascertain to what extent their activation was correlated. We presented continuous 20 Hz vibrotactile stimuli (range of flutter) concurrently to the left and right index fingers of healthy human volunteers. An arrow cue instructed subjects in a trial-by-trial fashion to attend to the left or right index finger and to detect rare target events that were embedded in the vibrotactile stimulation streams. We found blood oxygen level-dependent (BOLD) attentional modulation in primary somatosensory cortex (SI), mainly covering Brodmann area 1, 2, and 3b, as well as in secondary somatosensory cortex (SII), contralateral to the to-be-attended hand. Furthermore, attention to the right (dominant) hand resulted in additional BOLD modulation in left posterior insula. All of the effects were caused by an increased activation when attention was paid to the contralateral hand, except for the effects in left SI and insula. In left SI, the effect was related to a mixture of both a slight increase in activation when attention was paid to the contralateral hand as well as a slight decrease in activation when attention was paid to the ipsilateral hand (i.e., the tactile distraction condition). In contrast, the effect in left posterior insula was exclusively driven by a relative decrease in activation in the tactile distraction condition, which points to an active inhibition when tactile information is irrelevant. Finally, correlation analyses indicate a linear relationship between attention effects in intrahemispheric somatosensory cortices, since attentional modulation in SI and SII were interrelated within one hemisphere but not across hemispheres. All in all, our results provide a basis for future research on sustained attention to continuous vibrotactile stimulation in the range of flutter.     

Face or hand,not both: perceptual correlates of reafferentation in a former amputee

The topography of the somatosensory maps of our body can be largely shaped by alterations of peripheral sensory inputs. Following hand amputation, the hand cortical territory becomes responsive to facial cutaneous stimulation. Amputation-induced remapping, however, reverses after transplantation, as the grafted hand (re)gains its sensorimotor representation. Here, we investigate hand tactile perception in a former amputee by touching either grafted hand singly or in combination with another body part. The results showed that tactile sensitivity recovered rapidly, being remarkably good 5 months after transplant. In the right grafted hand, however, the newly acquired somatosensory awareness was strikingly hampered when the ipsilateral face was touched simultaneously, i.e., right face perception extinguished right hand perception. Ipsilateral face-hand extinction was present in the formerly dominant right hand 5 months after transplant and eventually disappeared 6 months afterwards. Control conditions' results showed that right hand tactile awareness was not extinguished either by contralateral left face and left hand stimulation or ipsilateral stimulation of the arm, which is bodily close to, but cortically far from, the hand. We suggest that ipsilateral face-hand extinction is a perceptual counterpart of the remapping that occurs after allograft and eyewitnesses the inherently competitive nature of sensory representations.     

The Efficiency of the Brain-Computer Interfaces Based on Motor Imagery with Tactile and Visual Feedback

In this study we compared tactile and visual feedbacks for the motor imagery-based brain–computer interface (BCI) in five healthy subjects. A vertical green bar from the center of the fixing cross to the edge of the screen was used as visual feedback. Vibration motors that were placed on the forearms of the right and the left hands and on the back of the subject’s neck were used as tactile feedback. A vibration signal was used to confirm the correct classification of the EEG patterns of the motor imagery of right and left hand movements and the rest task. The accuracy of recognition in the classification of the three states (right hand movement, left hand movement, and rest) in the BCI without feedback exceeded the random level (33% for the three states) for all the subjects and was rather high (67.8% ± 13.4% (mean ± standard deviation)). Including the visual and tactile feedback in the BCI did not significantly change the mean accuracy of recognition of mental states for all the subjects (70.5% ± 14.8% for the visual feedback and 65.9% ± 12.4% for the tactile feedback). The analysis of the dynamics of the movement imagery skill in BCI users with the tactile and visual feedback showed no significant differences between these types of feedback. Thus, it has been found that the tactile feedback can be used in the motor imagery-based BCI instead of the commonly used visual feedback, which greatly expands the possibilities of the practical application of the BCI.     

Ultradian rhythms in the EEG and task performance

The purpose of this work was to investigate the presence of ultradian rhythms in: 1. levels of electroencephalographic activation; 2. interhemispheric correlation and 3. the performance of two cognitive tasks, and the correlation between these variables. Eight volunteers, aged 20 to 30, participated in the experiment. Two sessions were carried out: one from 0800 to 1400 on one day and the other from 1400 to 2000 another day. Samples of EEG activity were taken every 15 min at rest with eyes open in left and right temporal, central, parietal and occipital derivations referred to the ipsilateral earlobe the performance on two tasks, one logico-analytical (left hemisphere functions) and one spatial test (right hemisphere functions) was assessed. As control, body and environmental temperature were recorded. To test for the presence of ultradian rhythms, the data were subjected to a Fourier analysis. Different EEG variables showed rhythmicity throughout the sessions, principally with slow oscillation periods (3 and 6h); ultradian rhythms with 3h periods were also found in body temperature, while task performance showed no significant rhythmic patterns during sessions. Finally, no significant correlations were found between physiological variables evaluated and task performance.     

Small Bowel and Plasma Gastrin Rhythms in Cats

The purpose of this experiment was to study the possible role of the gastric antrum and small bowel in the rhythm(s) of plasma gastrin. The cat was used as the laboratory animal. Three groups of cats were provided with a gastric fistula for the study of gastric acid and plasma gastrin rhythms. The first group (N = 7) served as controls. A second group (N = 3) was antrectomized and later subjected to a 80% small bowel resection. Gastric acid secretions were collected every 30 min from 0800 to 2400. Blood samples for determination of gastrin were drawn every 2hr from 0800 to 2400. In control animals a circadian (i.e.<24hr) and 3 ultradian (i.e.<24 hr) rhythms were detected for acid output. In the antrectomized cats, circadian and ultradian rhythms were documented. After small bowel resection circadian and ultradian rhythms in gastric acid secretion were observed. For plasma gastrin, circadian and ultradian rhythms were found in the control cats. In the antrectomized cats no rhythms were observed. After small bowel resection an ultradian rhythm reappeared in these antrectomized cats. Removal of the antrum in the cat induces disappearance of circadian and ultradian rhythms of plasma gastrin but fails to modify the acid rhythms. Small bowel resection results in the reappearance of an ultradian rhythm for plasma gastrin and a shift in acrophase for the circadian rhythm in acid secretion.     

Small bowel and plasma gastrin rhythms in cats

The purpose of this experiment was to study the possible role of the gastric antrum and small bowel in the rhythm(s) of plasma gastrin. The cat was used as the laboratory animal. Three groups of cats were provided with a gastric fistula for the study of gastric acid and plasma gastrin rhythms. The first group (N = 7) served as controls. A second group (N = 3) was antrectomized and later subjected to a 80% small bowel resection. Gastric acid secretions were collected every 30 min from 0800 to 2400. Blood samples for determination of gastrin were drawn every 2 hr from 0800 to 2400. In control animals a circadian (i.e. approximately 24 hr) and 3 ultradian (i.e. less than 24 hr) rhythms were detected for acid output. In the antrectomized cats, circadian and ultradian rhythms were documented. After small bowel resection circadian and ultradian rhythms in gastric acid secretion were observed. For plasma gastrin, circadian and ultradian rhythms were found in the control cats. In the antrectomized cats no rhythms were observed. After small bowel resection an ultradian rhythm reappeared in these antrectomized cats. Removal of the antrum in the cat induces disappearance of circadian and ultradian rhythms of plasma gastrin but fails to modify the acid rhythms. Small bowel resection results in the reappearance of an ultradian rhythm for plasma gastrin and a shift in acrophase for the circadian rhythm in acid secretion.     

Circadian Rhythms in Competitive Sabre Fencers: Internal Desynchronization and Performance

During a 7-10 day span, circadian rhythms of sleep-wake, self-rated fatigue and mood, oral temperature, eye-hand skill and right and left hand grip strength were investigated in eight subjects: five males (21-28 years of age), members of the French sabre fencing team selected for the 1984 Olympic Games in Los Angeles, and three females (19-26 years of age) practicing fleuret (foil) fencing as a sports activity. On the average six measurements/day/variable/subject were performed. The single cosinor method showed that a circadian rhythm was detectable for only 26 out of the 56 time series (46.4%). Power spectrum analysis gave almost the same figure (19 out of 48: 39.5%) with regard to rhythms with τ=24hr indicating that with one exception (subject JFL) rhythms were internally desynchronized including differences τ between right and left hand grip strength rhythms for three subjects. Results suggest: (a) a physiologic synchronization of circadian rhythms may be a predictor of good performance; (b) however, internal desynchronization as shown previously may be a trivial phenomenon and thus does not imply in itself alterations of either health or performance; (c) chronobiologic methods should be recommended for a better understanding of changes in performance by those participating in competitive and other sports.     

Circadian Rhythms in Competitive Sabre Fencers: Internal Desynchronization and Performance

During a 7-10 day span, circadian rhythms of sleep-wake, self-rated fatigue and mood, oral temperature, eye-hand skill and right and left hand grip strength were investigated in eight subjects: five males (21-28 years of age), members of the French sabre fencing team selected for the 1984 Olympic Games in Los Angeles, and three females (19-26 years of age) practicing fleuret (foil) fencing as a sports activity. On the average six measurements/day/variable/subject were performed. The single cosinor method showed that a circadian rhythm was detectable for only 26 out of the 56 time series (46.4%). Power spectrum analysis gave almost the same figure (19 out of 48: 39.5%) with regard to rhythms with τ=24hr indicating that with one exception (subject JFL) rhythms were internally desynchronized including differences τ between right and left hand grip strength rhythms for three subjects. Results suggest: (a) a physiologic synchronization of circadian rhythms may be a predictor of good performance; (b) however, internal desynchronization as shown previously may be a trivial phenomenon and thus does not imply in itself alterations of either health or performance; (c) chronobiologic methods should be recommended for a better understanding of changes in performance by those participating in competitive and other sports.     

Effect of geomagnetic activity on the rhythm of resistance of rats to hypoxia

The resistance of male Wistar rats to acute hypoxia was estimated from the lifetime at an "altitude" of 11.5 km above sea level from 13 to 21 p.m. and in different seasons of a year. Identical types of rhythms (circaseptan, circasemiseptan, infradian, circadian, and ultradian) of geomagnetic activity and lifetime were revealed. It was found that the periods of basal rhythms either coincide or are multiple. It was shown that the rhythms of geomagnetic activity (including nonbasal rhythms) affect lifetime rhythms (especially ultradian rhythms). As the periods of the rhythms decrease, the number of rhythms for both parameters increase (ultradian rhythms are most numerous), and relative differences in the values of periods (they are minimal for ultradian rhythms) and the amplitudes of rhythms decrease.     

Circadian and Ultradian Rhythms in Blood Glucose and Plasma Insulin of Healthy Adults

The circadian and ultradian variations of blood glucose and plasma insulin have been characterized individually and as a group phenomenon in five healthy young adults studied while adhering as closely as possible to their usual routine of sleep, activity, meal content and timing. Three complementary methods were used to analyze the data: displaying raw data as a function of time; cosinor method according to Nelson and Halberg; and time series analyses as proposed by De Prins and Malbecq. The subjects were studied in the laboratory and their life routine were controlled, but very close to that of their habitual routine. They had mainly ultradian rhythms of blood glucose (mainly about 6 hr) and circadian rhythms of immunoreactive insulin (I.R.I.). Blood glucose ultradian rhythms seem to be mainly but not exclusively mealtime dependent, while I.R.I, circadian rhythms appear to be primarily endogenous in origin. Therefore, the role played by insulin in the control of blood glucose levels seems to be programmed on a circadian basis rather than by a time independent feedback phenomenon as postulated by the conventional homeostatic hypothesis. The advantage of this chronophysiologic approach is to consider circadian rhythms of both I.R.I. and insulin effectiveness as an adaptive phenomenon able to maintain blood sugar changes in the ultradian domain of rhythms.     

Characteristics of the interhemispheric EEG relationships in assessing the functional state of the human brain

In healthy subjects (11 right-handed men) reorganization was studied of intra- and interhemispheric correlation of the electrical brain activity at transition from the state of alertness to drowsiness. At the lowering of alertness level, the coherence of hemispheres symmetrical points changed not abruptly, with a tendency towards an increase at differently directed character of changes of combinations of separate physiological rhythms ranges. Comparison of the EEG coherence changes within the right and left hemispheres revealed a greater reactivity of the left (dominant) hemisphere. The reduction of the predominance (observed in the dominant hemisphere in alertness) of the degree of EEG conjunction, at transition to drowsiness, leads to smoothing of interhemispheric asymmetry in the organization of electrical brain processes.     

Ultradian Rhythm of Activity in Japanese Quail Groups under Semi-Natural Conditions during Ontogeny: Functional Aspects and Relation to Circadian Rhythm

The function of ultradian rhythms is not yet clearly elucidated. In particular, short-term rhythms are expressed during early ontogeny, especially in broods of precocial birds. We investigated the relationship between the clarity of the ultradian rhythm of the activity/rest cycle of a group of young Japanese quail (Coturnix japonica) and the level of social synchronisation and spatial cohesion between the birds within that group. The subjects were descended from two lines selected for either very pronounced rhythmic or arrhythmic circadian activity. We found a positive relationship between the clarity of the ultradian rhythm of the activity/rest cycle when birds were young and the clarity of the circadian rhythm of feeding activity when birds were older, but still immature. The temporal organisation of the behaviour of the chicks from these two lines was observed in outdoor aviaries, when they were 4, 8, 12 and 15 days old. The mean ultradian period expressed by groups of 12 chicks was variable, with a minimum of 6 minutes. The ultradian period lengthened regularly as chicks grew older, and reached approximately 40 min on day 15. The clarity of the ultradian rhythmicity of group activity was linked to the level of inter-individual social synchronisation and of spatial cohesion; the more pronounced the ultradian rhythms of a group, the greater the temporal and spatial cohesion of the chicks within the group. Moreover, these characteristics varied with the age of the chicks. Finally, chicks in the less rhythmic groups weighed less. These results stress the adaptive value of this temporal organisation strategy under natural conditions.     

Ultradian Rhythm of Activity in Japanese Quail Groups under Semi-Natural Conditions during Ontogeny: Functional Aspects and Relation to Circadian Rhythm

The function of ultradian rhythms is not yet clearly elucidated. In particular, short-term rhythms are expressed during early ontogeny, especially in broods of precocial birds. We investigated the relationship between the clarity of the ultradian rhythm of the activity/rest cycle of a group of young Japanese quail (Coturnix japonica) and the level of social synchronisation and spatial cohesion between the birds within that group. The subjects were descended from two lines selected for either very pronounced rhythmic or arrhythmic circadian activity. We found a positive relationship between the clarity of the ultradian rhythm of the activity/rest cycle when birds were young and the clarity of the circadian rhythm of feeding activity when birds were older, but still immature. The temporal organisation of the behaviour of the chicks from these two lines was observed in outdoor aviaries, when they were 4, 8, 12 and 15 days old. The mean ultradian period expressed by groups of 12 chicks was variable, with a minimum of 6 minutes. The ultradian period lengthened regularly as chicks grew older, and reached approximately 40 min on day 15. The clarity of the ultradian rhythmicity of group activity was linked to the level of inter-individual social synchronisation and of spatial cohesion; the more pronounced the ultradian rhythms of a group, the greater the temporal and spatial cohesion of the chicks within the group. Moreover, these characteristics varied with the age of the chicks. Finally, chicks in the less rhythmic groups weighed less. These results stress the adaptive value of this temporal organisation strategy under natural conditions.     

Impaired mirror-image imitation in Asperger and high-functioning autistic subjects

Imitation is crucial for proper development of social and communicative skills. Here, we argue that, based on an error analysis of a behavioral imitation task, adult Asperger and high-functioning autistic subjects suffer from an intriguing deficit of imitation: they lack the natural preference for imitation in a mirror-image fashion. The imitation task consisted of a simple movement sequence of putting a pen with the left or right hand into a green or a blue cup using one of two possible grips. The subjects were asked to imitate the experimenter's hand movements either using the crossed hand (e.g., the subject's right hand corresponding to the experimenter's right hand) for imitation or to imitate as if looking in a mirror (e.g., the subject's left hand corresponding to the experimenter's right hand). When people normally view other persons face-to-face, they prefer to imitate as in a mirror, and observation of mirror-image-like movements speeds up performance in nonimitative tasks. However, our autistic subjects, defective in social cognition, did not profit from mirror-image movements of others. These results provide a new insight into the difficulties that autistic subjects face in viewing and understanding actions of others.     

Temporal structure of in vivo adrenal secretory activity estimated by deconvolution analysis

Circadian and ultradian rhythms of plasma cortisol concentrations have been documented under physiological conditions in diverse animal species. Using a novel, biophysical convolution model to remove subject-specific metabolic clearance rates, we have now estimated spontaneous adrenal secretory events in vivo. The latter were characterized by prominent ultradian rhythms of discrete secretory bursts with periodicities averaging 32, 46, 76, and 130 min. These ultradian cortisol secretory rhythms represented a 17- to 240-fold larger fraction of circadian secretory variations than did cortisol concentration rhythms. We conclude that deconvolution analysis can unmask underlying ultradian rhythms in adrenal secretory activity in vivo.     

Short period leaf movements in Oxalis regnellii

Oxalis regnellii Mig. is a trifoliate plant, and the three leaflets usually show synchronized up and down movements with a circadian period of 26–27 h. The three leaflets can also perform desynchronized ultradian oscillations, and we report on such rhythms under different conditions. A study of the occurrence of ultradian leaf movement rhythms as a function of irradiance is presented. At an irradiance of approximately 1 μW cm⁻², the occurrence was maximal and ca 30%. The periods varied from 5 to 15 h. Four other cases of ultradian rhythms in different conditions are also presented. In one case spontaneous ultradian rhythms occurred, and in another, two of the leaflets showed ultradian rhythms when the third leaflet had received a light pulse. In two more cases, the three leaflets on a leaf were separated by physical cuts along the petiole between the pulvini; in both cases the period was approximately 5 h. Possible mechanisms to explain the ultradian rhythms in Oxalis regnelli are discussed.