Single Session Imaging of Cerebellum at 7 Tesla: Obtaining Structure and Function of Multiple Motor Subsystems in Individual Subjects

The recent increase in the use of high field MR systems is accompanied by a demand for acquisition techniques and coil systems that can take advantage of increased power and accuracy without being susceptible to increased noise. Physical location and anatomical complexity of targeted regions must be considered when attempting to image deeper structures with small nuclei and/or complex cytoarchitechtonics (i.e. small microvasculature and deep nuclei), such as the brainstem and the cerebellum (Cb). Once these obstacles are overcome, the concomitant increase in signal strength at higher field strength should allow for faster acquisition of MR images. Here we show that it is technically feasible to quickly and accurately detect blood oxygen level dependent (BOLD) signal changes and obtain anatomical images of Cb at high spatial resolutions in individual subjects at 7 Tesla in a single one-hour session. Images were obtained using two high-density multi-element surface coils (32 channels in total) placed beneath the head at the level of Cb, two channel transmission, and three-dimensional sensitivity encoded (3D, SENSE) acquisitions to investigate sensorimotor activations in Cb. Two classic sensorimotor tasks were used to detect Cb activations. BOLD signal changes during motor activity resulted in concentrated clusters of activity within the Cb lobules associated with each task, observed consistently and independently in each subject: Oculomotor vermis (VI/VII) and CrusI/II for pro- and anti-saccades; ipsilateral hemispheres IV-VI for finger tapping; and topographical separation of eye- and hand- activations in hemispheres VI and VIIb/VIII. Though fast temporal resolution was not attempted here, these functional patches of highly specific BOLD signal changes may reflect small-scale shunting of blood in the microvasculature of Cb. The observed improvements in acquisition time and signal detection are ideal for individualized investigations such as differentiation of functional zones prior to surgery.     

Changes in functional connectivity of motor zones in the course of treatment with a regent multimodal complex exoskeleton in neurorehabilitation of post-stroke patients

The effect of a treatment course with a Regent multimodal complex exoskeleton (MCE) on the reorganization of cortical locomotor zones was studied in 14 patients with post-stroke hemiparesis, mainly in the chronic stage of the disease. Specific activation zones were identified prior to treatment in the primary sensorimotor and supplementary motor areas and the inferior parietal lobules of both affected and healthy hemispheres by functional magnetic resonance imaging (fMRI) used in a special passive sensorimotor paradigm. After a treatment course with the MCE, temporal characteristics of walking were found to improve, which was accompanied by a decrease in the activation zones of the inferior parietal lobules, especially in the healthy hemisphere, and a significant increase in the activation zones of the primary sensorimotor and supplementary motor areas. Significant changes in intrahemispheric and interhemispheric interactions were revealed by analyzing the functional connectivity of the zones under study before and after a course of treatment with the MCE.     

Motor timing and more--additional options using advanced registration and evaluation of tapping data.

Motor coordination in multi-tasking situations is relevant to everyday life, since numerous daily activities require the performance of more than one task simultaneously. Investigations into this topic often use dual-task experiments like bimanual tapping, with different instructions for the right and left hands, such as to tap repetitively with the right index finger at a given frequency and to concurrently execute a single tap in response to a go signal with the left index finger. A basic experimental set-up for tapping consists of only a pace signal generator and ground contact sensors such as micro switches for observation of motor action. Evaluation of the binary on-off signals provided by these switches is quite simple, but the amount of information obtained is also limited. This paper presents a novel experimental design for tapping experiments with high-resolution recording of the complete time course of continuous finger movements. The evaluation procedures required for biomechanical and EMG data are described. The latter are based on sophisticated maximum-likelihood techniques, which is an example of progress in research using advanced biosignal processing.     

Computerized method for study of temporal characteristics of sensorimotor reactions in preschool and first-grade schoolchildren

A computerized technique for estimation of the reaction time of motor responses to visual stimuli was advanced. The testing includes three stages. The following kinds of reactions were studied: simple reactions at the first stage, simple choice between 2 and 4 alternatives at the second stage, and, finally, reactions of the complex choice between 2 and 4 alternatives at the third stage. The authors think that each kind of reactions reflects specific components of child's sensorimotor activity. It is planned to study the rate of ontogenetic development of different links included into the functional system of voluntary sensorimotor reactions (perceptual, motor, decision making and others) using the proposed technique.     

Features of a Simple Psychophysiological Reaction

The latency of a simple psychophysiological (visual motor) response (SPPR) was studied as dependent on the waiting time, which was the period between the previous response to a subsequent stimulus and was varied from 1 to 3000 ms. An ordinal approximation was used for the resulting monotonic dependence. The latency of the simple psychophysiological response at shorter intervals between the previous response and a subsequent stimulus was observed to be far greater than at longer intervals. The latency decreased with the increasing waiting time until 3–4 s after the previous response. The decrease included at least two components. The components were found to be interdependent. The decrease in latency was assumed to result from autoinhibition due to the previous response.     

Photosynthate allocation and productivity of latex vessels inHevea brasiliensis

Manipulations of production systems in rubber tree which were intended to improve sucrose translocation in tapped bark resulted in an increase of latex sucrose and of latex production and reduced the incidence of nonyielding laticiferous tissue. This was achieved by shortening the tapping cut from full to half spiral, by changing the descending direction into an ascending mode of tapping or by annual change-over of tapping panel allowing for a longer time the regeneration of bark removed above the location of the cut. The increase of latex yield did not result in a significant decrease in the growth of trees over a period of three years. Clonal differences in nonyielding bark appeared to be related to differences in sucrose depletion by tapping. In clone PB 235 which exhibited low latex sucrose, a reduction of tapping frequency resulted in an increase in sucrose level and in a decrease of bark “dryness” tending to an increase in total yield. The tapping manipulations examined did not affect latex flow characteristics such as the plugging index of latex vessels and the bursting index of lutoids. The results stress the importance of photosynthate allocation for the physiology of laticiferous system productivity and indicate the possibilities of improving assimilate economy in rubber trees. On mission as export of the International Atomic Energy Agency.     

Development of functional variability during the motor learning process of a complex cyclic movement

Traditionally, movement variability is considered an indicator for sensorimotor malfunctioning. However, functional movement variability is also a result of compensation mechanisms e.g. to account for prior movement deviations and is, therefore, crucial for stable movements. The aim of this study was to analyze functional variability during motor learning of a complex cyclic task.Thirteen young participants practised riding a Pedalo® slalom until they were able to complete the task without errors. Since trunk movements are controlled with high priority, we analyzed trunk kinematics as a result parameter. Since lower extremities affect the result parameter, foot, thigh and pelvis kinematics are considered execution parameters. The movement variability for result and execution parameters was determined for the first (poor performance), an intermediate (medium performance) and the last (good performance) training sessions. Furthermore, the variability ratio (execution/result parameter) was calculated as a measure of functional variability.Movement variability of the result parameter decreased significantly with increasing expertise. In contrast, movement variability of all execution parameters increased significantly from measurements representing poor to medium performance. No change from medium to good performance was found. Functional variability increased over time in all execution parameters.Since the movement variability of all execution parameters did not decrease with increasing Pedalo performance, applying a traditional interpretation approach of movement variability would have led to completely wrong conclusions. Possible mechanisms explaining the increased movement variability are discussed. The variability ratio seems to be the only parameter that can reveal improved sensorimotor functioning during all analyzed stages of motor learning.     

MEG responses during rhythmic finger tapping in humans to phasic stimulation and their interpretation based on neural mechanisms

 The phase-resetting experiment was applied to human periodic finger tapping to understand how its rhythm is controlled by the internal neural clock that is assumed to exist. In the experiment, the right periodic tapping movement was disturbed transiently by a series of left finger taps in response to impulsive auditory cues presented randomly at various phases within the tapping cycle. After each left finger tap, the original periodic tapping was reestablished within several tapping cycles. Influences of the disturbance on the periodic right finger tapping varied depending on the phase of the periodic right finger tapping at which each left finger tap was made. It was confirmed that the periodic tapping was disturbed not by the auditory cues but by the left finger taps. Based on this fact, in this paper each single left tap was considered as the stimulus, and the phase of the periodic tapping of the right index finger when the left tap was executed as the phase of the stimulus. Responses of the neural activities (magnetoencephalography, MEG), the tapping movement, and the corresponding muscle activities (electromyography) were simultaneously measured. Phase-resetting curves (PRCs) representing the degree of phase reset as a function of the phase of the stimulus were obtained both for the left sensorimotor cortex MEG response and for the right index finger tapping response. The shapes of both PRCs were similar, suggesting that the phase reset of the left sensorimotor cortex activities and that of the finger tapping rhythm were the same. Four out of eight subjects showed type-0 reset in Winfree's definition, and the others showed type-1 reset. For general limit-cycle oscillators, type-0 reset is obtained for relatively strong perturbations and type 1 for weak perturbations. It was shown that the transient response of MEG to the single left tap stimuli in type-0 subjects, where the phase was progressively reset, were different from those in type-1 subjects. Based on detailed analysis of the differences, a neural network model for the phase reset of the tapping rhythm is proposed. Received: 10 February 2000 / Accepted in revised form: 15 January 2002     

Evaluation of EEG Oscillatory Patterns and Cognitive Process during Simple and Compound Limb Motor Imagery

Motor imagery (MI), sharing similar neural representations to motor execution, is regarded as a window to investigate the cognitive motor processes. However, in comparison to simple limb motor imagery, significantly less work has been reported on brain oscillatory patterns induced by compound limb motor imagery which involves several parts of limbs. This study aims to investigate differences of the electroencephalogram (EEG) patterns as well as cognitive process between simple limb motor imagery and compound limb motor imagery. Ten subjects participated in the experiment involving three tasks of simple limb motor imagery (left hand, right hand, feet) and three tasks of compound limb motor imagery (both hands, left hand combined with right foot, right hand combined with left foot). Simultaneous imagination of different limbs contributes to the activation of larger cortical areas as well as two estimated sources located at corresponding motor areas within beta rhythm. Compared with simple limb motor imagery, compound limb motor imagery presents a network with more effective interactions overlying larger brain regions, additionally shows significantly larger causal flow over sensorimotor areas and larger causal density over both sensorimotor areas and neighboring regions. On the other hand, compound limb motor imagery also shows significantly larger 10–11 Hz alpha desynchronization at occipital areas and central theta synchronization. Furthermore, the phase-locking value (PLV) between central and occipital areas of left/right hand combined with contralateral foot imagery is significantly larger than that of simple limb motor imagery. All these findings imply that there exist apparent intrinsic distinctions of neural mechanism between simple and compound limb motor imagery, which presents a more complex effective connectivity network and may involve a more complex cognitive process during information processing.     

Phase relationships of cerebral cortex potentials in the rabbit during the execution of motor responses

EEG waves phase relations in the sensorimotor and visual cortical areas were studied in 12 rabbits before and during a motor reaction in response to light stimulation. Phase relations in the background activity were characterized by a considerable dispersion (from 26 to 45 degrees). Light stimulation increased the quantity of synphasic EEG oscillations in adjacent cortical points and stabilized the phase shift between EEG waves in the sensorimotor and visual cortical areas. Motor reactions of rabbits to light occurred when theta-rhythm with the most constant phase shift was observed in the EEG of these areas.     

Recognition of forward-masked complex and simple images

The accuracy and time of motor response in tests for visual recognition of simple (sets of horizontal and vertical lines, angles, and crosses) and complex (contour images of animate and inanimate objects) images forward-masked with stimuli of varying complexity were estimated in psychophysiological experiments. It was found that forward masking impaired recognition, the mask whose complexity was close to that of the given test image being the most efficient in each particular case. The masking effect was the strongest in the experiments where the sets of test and masking images coincided. Recognition of complex images proved to be more resistant to masking than recognition of simple images. The observed effects of forward masking are assumed to be determined by lateral inhibition and changes in the excitability cycle. The relative contributions of these mechanisms depend on the degree of similarity between the test and masking stimuli, as well as the hierarchical level of the visual cortex at which the test stimulus is “targeted.”     

Hormone therapy in postmenopausal women affects hemispheric asymmetries in fine motor coordination

Evidence exists that the functional differences between the left and right cerebral hemispheres are affected by age. One prominent hypothesis proposes that frontal activity during cognitive task performance tends to be less lateralized in older than in younger adults, a pattern that has also been reported for motor functioning. Moreover, functional cerebral asymmetries (FCAs) have been shown to be affected by sex hormonal manipulations via hormone therapy (HT) in older women. Here, we investigate whether FCAs in fine motor coordination, as reflected by manual asymmetries (MAs), are susceptible to HT in older women. Therefore, sixty-two postmenopausal women who received hormone therapy either with estrogen (E) alone (n = 15), an E-gestagen combination (n = 21) or without HT (control group, n = 26) were tested. Saliva levels of free estradiol and progesterone (P) were analyzed using chemiluminescence assays. MAs were measured with a finger tapping paradigm consisting of two different tapping conditions. As expected, postmenopausal controls without HT showed reduced MAs in simple (repetitive) finger tapping. In a more demanding sequential condition involving four fingers, however, they revealed enhanced MAs in favour of the dominant hand. This finding suggests an insufficient recruitment of critical motor brain areas (especially when the nondominant hand is used), probably as a result of age-related changes in corticocortical connectivity between motor areas. In contrast, both HT groups revealed reduced MAs in sequential finger tapping but an asymmetrical tapping performance related to estradiol levels in simple finger tapping. A similar pattern has previously been found in younger participants. The results suggest that, HT, and E exposure in particular, exerts positive effects on the motor system thereby counteracting an age-related reorganization.     

Correction of changes induced by toluene in the cortical and subcortical structures of albino rat brain

The number and weight of cells in the cortical and subcortical structures of the cerebral and cerebellar motor system in albino rats after a long-term exposure to toluene were determined. Toluene intoxication proved to kill projection neurons and interneurons in the sensorimotor cortex, ventrolateral thalamic nucleus, caudate nucleus, pallidum, red nucleus, and inferior olivary complex. The decreased number of cerebellar cells was mediated by atrophic changes as indicated by the decrease in the area and dry weight of Purkinje cells. The addition of plaferon LB to the diet attenuated the cytotoxic effect of toluene.     

The dynamics of the activating and inhibitory types of cortical neuron synchronization during the realization of a defensive reflex and internal inhibition

In the visual and sensorimotor areas of the neocortex and in the hippocampus of alert nonimmobilized rabbits, in response to combinations of light flashes with electrocutaneous limb stimulation an increase was observed of synchronization in the activity of the near-by neurones by activation by inhibitory type (coincidence of the presence and absence of impulse activity). In response to flashes against the light background--conditioned inhibitor--in the visual cortex synchronization of neurones increased by inhibitory type, and in the sensorimotor cortex and hippocampus changes of synchronization appeared, similar to the action of pain reinforcement but considerably weaker. The increase of synchronization by the activation type took place mainly in the neurones pairs with unidirected increase of impulses frequency and by the inhibitory one--with its decrease. Along with this, in a considerable part of neurones pairs both changes of synchronization appeared at the impulses frequency changes of different direction.     

Abnormal Electrophysiological Motor Responses in Huntington’s Disease: Evidence of Premanifest Compensation

Background

Huntington''s disease (HD) causes progressive motor dysfunction through characteristic atrophy. Changes to neural structure begin in premanifest stages yet individuals are able to maintain a high degree of function, suggesting involvement of supportive processing during motor performance. Electroencephalography (EEG) enables the investigation of subtle impairments at the neuronal level, and possible compensatory strategies, by examining differential activation patterns. We aimed to use EEG to investigate neural motor processing (via the Readiness Potential; RP), premotor processing and sensorimotor integration (Contingent Negative Variation; CNV) during simple motor performance in HD.

Methods

We assessed neural activity associated with motor preparation and processing in 20 premanifest (pre-HD), 14 symptomatic HD (symp-HD), and 17 healthy controls. Participants performed sequential tapping within two experimental paradigms (simple tapping; Go/No-Go). RP and CNV potentials were calculated separately for each group.

Results

Motor components and behavioural measures did not distinguish pre-HD from controls. Compared to controls and pre-HD, symp-HD demonstrated significantly reduced relative amplitude and latency of the RP, whereas controls and pre-HD did not differ. However, early CNV was found to significantly differ between control and pre-HD groups, due to enhanced early CNV in pre-HD.

Conclusions

For the first time, we provide evidence of atypical activation during preparatory processing in pre-HD. The increased activation during this early stage of the disease may reflect ancillary processing in the form of recruitment of additional neural resources for adequate motor preparation, despite atrophic disruption to structure and circuitry. We propose an early adaptive compensation mechanism in pre-HD during motor preparation.     

Relationship between cerebral activity and movement frequency of maximal finger tapping

To examine the cerebral activity of the motor cortex during maximum movement, we measured regional cerebral blood flow (rCBF) in twelve normal volunteers, using near infrared spectroscopy (NIRS). Repetitive tapping of the right index finger was performed at 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, and 4.5 Hz, and during maximum effort (ME). The relative increase rate of rCBF during movement beginning with a resting condition was calculated for each movement condition. The left primary sensorimotor cortex showed significant activation during ME compared to the other frequencies. The rapid increase of rCBF was seen immediately after the initiation of finger tapping at all the tested frequencies but showed no increase following that. However, the rCBF during ME continued to increase until the end of the task.Change of the integrated electromyogram (iEMG) for the frequency and change of rCBF for the frequency at all the tested frequencies showed similar tendencies.     

Recovery of Motor Deficit,Cerebellar Serotonin and Lipid Peroxidation Levels in the Cortex of Injured Rats

The sensorimotor cortex and the cerebellum are interconnected by the corticopontocerebellar (CPC) pathway and by neuronal groups such as the serotonergic system. Our aims were to determine the levels of cerebellar serotonin (5-HT) and lipid peroxidation (LP) after cortical iron injection and to analyze the motor function produced by the injury. Rats were divided into the following three groups: control, injured and recovering. Motor function was evaluated using the beam-walking test as an assessment of overall locomotor function and the footprint test as an assessment of gait. We also determined the levels of 5-HT and LP two and twenty days post-lesion. We found an increase in cerebellar 5-HT and a concomitant increase in LP in the pons and cerebellum of injured rats, which correlated with their motor deficits. Recovering rats showed normal 5-HT and LP levels. The increase of 5-HT in injured rats could be a result of serotonergic axonal injury after cortical iron injection. The LP and motor deficits could be due to impairments in neuronal connectivity affecting the corticospinal and CPC tracts and dysmetric stride could be indicative of an ataxic gait that involves the cerebellum.     

Accounting for movement increases sensitivity in detecting brain activity in Parkinson's disease

Parkinson's disease (PD) is manifested by motor impairment, which may impede the ability to accurately perform motor tasks during functional magnetic resonance imaging (fMRI). Both temporal and amplitude deviations of movement performance affect the blood oxygenation level-dependent (BOLD) response. We present a general approach for assessing PD patients' movement control employing simultaneously recorded fMRI time series and behavioral data of the patients' kinematics using MR-compatible gloves. Twelve male patients with advanced PD were examined with fMRI at 1.5T during epoch-based visually paced finger tapping. MR-compatible gloves were utilized online to quantify motor outcome in two conditions with or without dopaminergic medication. Modeling of individual-level brain activity included (i) a predictor consisting of a condition-specific, constant-amplitude boxcar function convolved with the canonical hemodynamic response function (HRF) as commonly used in fMRI statistics (standard model), or (ii) a custom-made predictor computed from glove time series convolved with the HRF (kinematic model). Factorial statistics yielded a parametric map for each modeling technique, showing the medication effect on the group level. Patients showed bilateral response to levodopa in putamen and globus pallidus during the motor experiment. Interestingly, kinematic modeling produced significantly higher activation in terms of both the extent and amplitude of activity. Our results appear to account for movement performance in fMRI motor experiments with PD and increase sensitivity in detecting brain response to levodopa. We strongly advocate quantitatively controlling for motor performance to reach more reliable and robust analyses in fMRI with PD patients.     

Cerebral Activations Related to Writing and Drawing with Each Hand

BackgroundWriting is a sequential motor action based on sensorimotor integration in visuospatial and linguistic functional domains. To test the hypothesis of lateralized circuitry concerning spatial and language components involved in such action, we employed an fMRI paradigm including writing and drawing with each hand. In this way, writing-related contributions of dorsal and ventral premotor regions in each hemisphere were assessed, together with effects in wider distributed circuitry. Given a right-hemisphere dominance for spatial action, right dorsal premotor cortex dominance was expected in left-hand writing while dominance of the left ventral premotor cortex was expected during right-hand writing.MethodsSixteen healthy right-handed subjects were scanned during audition-guided writing of short sentences and simple figure drawing without visual feedback. Tapping with a pencil served as a basic control task for the two higher-order motor conditions. Activation differences were assessed with Statistical Parametric Mapping (SPM).ResultsWriting and drawing showed parietal-premotor and posterior inferior temporal activations in both hemispheres when compared to tapping. Drawing activations were rather symmetrical for each hand. Activations in left- and right-hand writing were left-hemisphere dominant, while right dorsal premotor activation only occurred in left-hand writing, supporting a spatial motor contribution of particularly the right hemisphere. Writing contrasted to drawing revealed left-sided activations in the dorsal and ventral premotor cortex, Broca’s area, pre-Supplementary Motor Area and posterior middle and inferior temporal gyri, without parietal activation.DiscussionThe audition-driven postero-inferior temporal activations indicated retrieval of virtual visual form characteristics in writing and drawing, with additional activation concerning word form in the left hemisphere. Similar parietal processing in writing and drawing pointed at a common mechanism by which such visually formatted information is used for subsequent sensorimotor integration along a dorsal visuomotor pathway. In this, the left posterior middle temporal gyrus subserves phonological-orthographical conversion, dissociating dorsal parietal-premotor circuitry from perisylvian circuitry including Broca''s area.     

Individual differences in motor skills ability affect the self-regulation of heart rate

Twenty males who scored relatively high on the rotor-pursuit motor skills task (High performance group) were given seven 2-minute trials to increase heart rate and seven 2-minute trials to decrease heart rate, as were 20 males who scored relatively low on the rotor-pursuit task (Low performance group). Visual analogue feedback was not provided during the first and last acceleration and deceleration trials but was presented during all other trials. Both groups of subjects were able to decrease heart rate significantly with and without feedback. Subjects in the High performance group were able to increase heart rate significantly with feedback and could generalize this increase to a no-feedback trial following feedback trials. Subjects in the Low performance group could not increase heart rate with or without feedback. Changes in respiration rate paralleled those noted for heart rate, but changes in chin electromyographic activity generally did not parallel the heart rate results. The heart rate data are discussed in terms of motor skills theories of self-regulation of heart rate.