Insufficiency of trunk extension and impaired control of muscle force in Parkinson's disease with camptocormia.

OBJECTIVE: To examine the aetiology of parkinsonian camptocormia, a non-fixed pathological forward bending of the trunk, by measuring trunk muscle activation and force regulation in Parkinson patients with (PD + CC) and without (PD) camptocormia matched for disease severity, and in age- and sex-matched healthy controls (HC). METHODS: The isometric forces of trunk extension and flexion were measured in PD + CC, PD and HC. Neuromuscular efficiency (increase of extension force per increase of paravertebral muscle surface electromyography signal) and the ability to maintain a constant submaximal trunk extension force were examined. RESULTS: Peak trunk extension force was significantly lower in PD + CC and PD than in HC, with PD + CC non-significantly weaker than PD. Compared with HC and with PD, the neuromuscular efficiency of trunk extension was significantly reduced in PD + CC. The variability of the force output (coefficient of variation) was significantly larger for PD + CC than for HC or PD. CONCLUSION: The reduced neuromuscular efficiency of trunk extension separates PD + CC from PD. Moreover, control of the trunk extensor force is impaired in PD + CC. SIGNIFICANCE: There is weakness and a force control deficit in parkinsonian camptocormia suggesting a disturbed sensory-motor integration, which may contribute to myopathic changes in the trunk extensor muscles.

Motor cortical representation of the pelvic floor muscles.

PURPOSE: Pelvic floor muscle training involves rhythmical voluntary contractions of the external urethral sphincter and ancillary pelvic floor muscles. The representation of these muscles in the motor cortex has not been located precisely and unambiguously. We used functional magnetic resonance imaging to determine brain activity during slow and fast pelvic floor contractions. MATERIALS AND METHODS: Cerebral responses were recorded in 17 healthy male volunteers, 21 to 47 years old, with normal bladder control. Functional magnetic resonance imaging was performed during metronome paced slow (0.25 Hertz) and fast (0.7 Hertz) contractions of the pelvic floor that mimicked the interruption of voiding. To study the somatotopy of the cortical representations, flexion-extension movements of the right toes were performed as a control task. RESULTS: Functional magnetic resonance imaging during pelvic floor contractions detected activity of the supplementary motor area in the medial wall and of the midcingulate cortex, insula, posterior parietal cortex, putamen, thalamus, cerebellar vermis and upper ventral pons. There were no significant differences in activation between slow and fast contractions. Toe movements involved significantly stronger activity of the paracentral lobule (ie the medial primary motor cortex) than did the pelvic floor contractions. Otherwise the areas active during pelvic floor and leg muscle contractions overlapped considerably. CONCLUSIONS: The motor cortical representation of pelvic floor muscles is located mostly in the supplementary motor area. It extends further ventrally and anteriorly than the representation of distal leg muscles.

The Müller-Lyer illusion: investigation of a center of gravity effect on the amplitudes of saccades.

Previous research has compared the effects of visual illusions on perception with their effects on action to investigate if the action system and the perceptual system use different or common codes. Appropriate conclusions based on this comparison rely on effects that reflect the internal parameter estimates of the action and of the perceptual system. We investigated an additional factor that can possibly change the amplitudes of saccades along the Müller-Lyer illusion, the center of gravity effect. It refers to the finding that the endpoints of saccades can be diverted from the target point in the direction of the center of gravity of a stimulus configuration. We measured the perceptual (adjustment method) and the action effects (amplitudes of saccades) of the illusion. In addition, we let subjects carry out saccades along Müller-Lyer figures and a neutral figure that appeared to have the same size (but differed in actual sizes). The amplitudes of saccades differed for these figures. This was interpreted as evidence for a center of gravity effect. Its quantification allowed a correction of the action effect, which was then remarkably similar to the perceptual effect. Our results are in agreement with the notion of a common internal representation for perception and action.

Control of bladder sensations: an fMRI study of brain activity and effective connectivity.

When the bladder is fairly full, the desire to void can be suppressed, but it can also be called forth deliberately. We studied brain activity during such intentional modulations of bladder sensation in 33 healthy volunteers (17 women, 16 men). The supplementary motor area, midcingulate cortex, insula, frontal operculum, and right prefrontal cortex were consistently more active when the desire to void was enhanced without allowing urine to pass ("attempted micturition") than during a baseline task when bladder sensations were suppressed. The right anterior insula and midbrain periaquaeductal grey (PAG) were more active at higher than at lower bladder volumes. Responses of the right thalamus and several other right-hemispherical regions were stronger in women than in men. Using the psychophysiological interaction (PPI) method, we found that the midcingulate cortex had stronger connectivity (indicated by parallel co-variations of the activation time series) with the PAG and medial motor areas during "attempted micturition" than during the baseline task, possibly reflecting monitoring of urethral sphincter contractions. Conversely, the left and right insula showed decreased connectivity with many other brain regions during "attempted micturition", possibly due to predominant processing of bladder-afferent input. Intentional modulations of the desire to void change the effective connectivity of supraspinal regions involved in bladder control.

Monitoring of CBFV and time characteristics of oxygen-induced acute CNS toxicity in humans.

BACKGROUND: Hyperbaric oxygen can cause central nervous system (CNS) toxicity with seizures. We tested the hypothesis that CNS toxicity could be predictable by cerebral blood flow velocity (CBFV) monitoring. METHOD: We monitored 369 mandatory oxygen tolerance tests (30 min, 280 kPa O(2)) by video-documentation and since May 2005 by additional CBFV registration (n = 61). RESULTS: The onset of early manifestations of CNS toxicity was documented in 11 of 369 tests within 22 +/- 3 min. These included twitches and/or agitation, 6 of 11 and tonic-clonic seizures in 5 of 11 cases. In both cases with CBFV monitoring, an increase in CBFV preceded symptom onset, once followed by seizure, once without seizure after timely oxygen reduction. CONCLUSIONS: During exposure to 280 kPa oxygen at rest a constant delay of approximately 20 min precedes the onset of central nervous oxygen toxicity. An increase in CBFV may indicate the impending seizure.

Brain activity is similar during precision and power gripping with light force: an fMRI study.

Handgrips can be broadly classified into precision and power grips. To compare central neuronal control of these tasks, functional magnetic resonance imaging was used in 14 healthy right-handed volunteers, who repetitively squeezed non-flexible force transducers with a precision grip and a power grip of the dominant hand. The relative grip force levels and movement rates (0.45 Hertz) of both tasks were comparable. Peak isometric grip forces ranged between 1% and 10% of the maximum voluntary force. Reflecting the additional recruitment of extrinsic hand muscles and the higher absolute force, activation of the contralateral primary sensorimotor cortex (M1/S1) and ipsilateral cerebellum was significantly stronger during power than during precision grip. No brain areas exhibited stronger activity during the precision grip than during the power grip. The left M1/S1 and right cerebellum showed a positive linear relationship with the grip force, while the right angular gyrus and left superior frontal gyrus showed a gradual increase in activity when less force was applied. However, these force-dependent modulations of brain activity were similar for the precision and power grip tasks. No brain region was specifically activated during one task but not during the other. Activity during precision gripping did not exceed the activity associated with power gripping possibly because the precision grip task was not challenging enough to call on dexterous fine motor control.

Asymmetry of arm-swing not related to handedness.

This study systematically investigated the symmetry of arm-swing kinematics in 16 normal subjects (8 right-handed, 8 left-handed) during treadmill locomotion, including forward walking (2-6 km/h), running (8 km/h), and backward walking (4 km/h). Kinematic data of both sides were compared. Significant differences between the left and right amplitudes of arm-swing (p<0.05) were detected in 47 of the 96 gait trials (16 subjects x 6 conditions). The mean magnitude of the side differences was 8.6 cm during forward walking (averaged across all subjects). The mean index of asymmetry of 12.5+/-24.0 (+/-S.D.) indicated a trend towards left arm-swing preference. In 10 of the 16 subjects, the individual direction of the arm-swing asymmetry could be reproduced across different velocities and locomotor modes. The asymmetry was not related to handedness, nor was it related to asymmetrical leg movements. The first comprehensive normative data of arm-swing asymmetry during treadmill walking are provided. A certain degree of asymmetry is physiological.

Activation of the supplementary motor area (SMA) during voluntary pelvic floor muscle contractions--an fMRI study.

To identify cortical and subcortical regions involved in voluntary pelvic floor muscle control, functional magnetic resonance imaging (fMRI) was performed at 1.5 T in thirty healthy subjects (15 women, 15 men). The participants performed rhythmical (1 Hz) pelvic floor muscle contractions, which imitated the repetitive interruption of voiding. Since previous reports concerning the representation of pelvic floor muscles in the cortex of the medial wall are inconsistent, a conservative statistical threshold (FWE-corrected P<0.05) was used to detect the most robust foci of activation, and cytoarchitectonic probability maps were used to correlate the results with structural anatomical information. We found a strong and consistent recruitment of the supplementary motor area (SMA), with foci of peak activity located in the posterior portion of the SMA, suggesting that this region is specifically involved in voluntary pelvic floor muscle control. Further significant activations were identified bilaterally in the frontal opercula, the right insular cortex and the right supramarginal gyrus. They may reflect the attentive processing and evaluation of visceral sensations. Weaker signals were detected in the primary motor cortex (M1) and the dorsal pontine tegmentum. There was no significant correlation between bladder volumes and brain activation induced by pelvic floor muscle contractions. We found no significant gender-related differences.

Grasp effects of the Ebbinghaus illusion are ambiguous.

The assumption that the Ebbinghaus/Titchener illusion deceives perception but not grasping, which would confirm the two-visual-systems hypothesis (TVSH) as proposed by Milner and Goodale (The visual brain in action, 1995), has recently been challenged. Franz et al. (Exp Brain Res 149:470-477, 2003) found that the illusion affects both perception and grasping, and showed that the effect of the illusion on the peak grip aperture (PGA) cannot be accounted for by different sizes of the gap that separates the central target disk from the surrounding flankers. However, it is not yet clear if the presence of flankers per se influences grasping. We therefore compared kinematic parameters of prehension, using the Ebbinghaus illusion, and a neutral control condition where normal subjects grasped a disk without any flankers. In accordance with the well-known effects of the illusion on perceived size, the PGA was smaller when the target disk was surrounded by large flankers, and larger when it was encircled by small flankers. However, the largest PGA values were reached in the neutral control condition. Hence the presence of flankers leads to a general reduction of the PGA, possibly because the flankers are regarded as obstacles. This 'reduction effect' casts doubts on how appropriate it is to directly compare perceptual measures and PGA values when using the Ebbinghaus illusion. Even smaller effects of the illusion on the PGA compared to larger perceptual effects cannot be unequivocally interpreted.

Effector-independent representations of simple and complex imagined finger movements: a combined fMRI and TMS study.

Kinesthetic motor imagery and actual execution of movements share a common neural circuitry. Functional magnetic resonance imaging was used in 12 right-handed volunteers to study brain activity during motor imagery and execution of simple and complex unimanual finger movements of the dominant and the nondominant hand. In the simple task, a flexible object was rhythmically compressed between thumb, index and middle finger. The complex task was a sequential finger-to-thumb opposition movement. Premotor, posterior parietal and cerebellar regions were significantly more active during motor imagery of complex movements than during mental rehearsal of the simple task. In 10 of the subjects, we also used transcranial magnetic brain stimulation to examine corticospinal excitability during the same motor imagery tasks. Motor-evoked potentials increased significantly over values obtained in a reference condition (visual imagery) during imagery of the complex, but not of the simple movement. Imagery of finger movements of either hand activated left dorsal and ventral premotor areas and the supplementary motor cortex regardless of task complexity. The effector-independent activation of left premotor areas was particularly evident in the simple motor imagery task and suggests a left hemispherical dominance for kinesthetic movement representations in right-handed subjects.

Grip force parameters in precision grip of individuals with myelomeningocele.

The aim of this study was to characterize impairments of hand function in individuals with myelomeningocele (MMC) using a quantitative method. A grip-lift task was studied in 29 individuals with MMC (17 females, 12 males; mean age 12 years 4 months, SD 5 years 6 months; range 4 to 28 years) and 29 age- and sex-matched control participants. A small object (weight 200 g) was grasped and lifted with a precision grip of the dominant hand and grip forces (GF) and time intervals were measured. Sensibility was examined with a two-point discrimination test. In those with MMC, the latency between GF onset of the thumb and index finger and ensuing preload duration were both significantly prolonged (p<0.01). Fingertip forces were excessively high and variable. Several parameters differed significantly between those with MMC and control individuals: GF peak, GF at start of loading, mean GF, and the SDs of the GF during static holding. Although the two-point discrimination task indicated deficits of sensibility, these did not correlate with grip force parameters. Results demonstrate that fine motor skills in patients with MMC are impeded by slowness and inadequate adjustments of manipulative forces.

Human brain activity in the control of fine static precision grip forces: an fMRI study.

Dexterous manipulation of delicate objects requires exquisite control of fingertip forces. We have used functional magnetic resonance imaging to identify brain regions involved in the skillful scaling of these forces when normal human subjects (n = 8) held with precision grip a small object (weight 200 g) in the dominant right hand. In one condition, they used their normal, automatically scaled grip force. The object was held gently in a second condition; the isometric grip force was maintained just above the critical level at which the object would have slipped. In a third condition, the force was increased to hold the object with a more firm grip. The supplementary and cingulate motor areas were significantly more active during the gentle force condition than during either of the other conditions in all subjects, despite weaker contractions of the hand muscles. In addition, the left primary sensorimotor cortex, the ventral premotor cortex and the left posterior parietal cortex were more strongly activated during gentle than during normal grasping. These novel results suggest that these regions are specifically involved in dexterous scaling of fingertip forces during object manipulation.

Comparative analysis of the gait disorder of normal pressure hydrocephalus and Parkinson's disease.

OBJECTIVES: Comparative gait analyses in neurological diseases interfering with locomotion are of particular interest, as many hypokinetic gait disorders have the same main features. The aim of the present study was (1) to compare the gait disturbance in normal pressure hydrocephalus and Parkinson's disease; (2) to evaluate which variables of the disturbed gait pattern respond to specific treatment in both diseases; and (3) to assess the responsiveness to visual and acoustic cues for gait improvement. METHODS: In study 1 gait analysis was carried out on 11 patients with normal pressure hydrocephalus, 10 patients with Parkinson's disease, and 12 age matched healthy control subjects, on a walkway and on a treadmill. In study 2, patients with normal pressure hydrocephalus were reinvestigated after removal of 30 ml CSF, and patients with Parkinson's disease after administration of 150 mg levodopa. In part 3 visual cues were provided as stripes fixed on the walkway and acoustic cues as beats of a metronome. RESULTS: The gait disorder in both diseases shared the feature of a reduced gait velocity, due to a diminished and highly variable stride length. Specific features of the gait disturbance in normal pressure hydrocephalus were a broad based gait pattern with outward rotated feet and a diminished height of the steps. After treatment in both diseases, the speed increased, due to an enlarged stride length, now presenting a lower variability. All other gait variables remained unaffected. External cues only mildly improved gait in normal pressure hydrocephalus, whereas they were highly effective in raising the stride length and cadence in Parkinson's disease. CONCLUSION: The gait pattern in normal pressure hydrocephalus is clearly distinguishable from the gait of Parkinson's disease. As well as the basal ganglia output connections, other pathways and structures most likely in the frontal lobes are responsible for the gait pattern and especially the disturbed dynamic equilibrium in normal pressure hydrocephalus. Hypokinesia and its responsiveness to external cues in both diseases are assumed to be an expression of a disturbed motor planning.

Quantitative assessment of mirror movements in children and adolescents with hemiplegic cerebral palsy.

Mirror movements in individuals with hemiplegic cerebral palsy (CP) may result from a reorganization of the central sensorimotor system. Motor performances of both hands were measured to characterize mirror activity (or mirroring) and hand functions in 22 participants (6 to 18 years) with hemiplegic CP and in 17 control participants. During a unimanual repetitive squeezing task, contractions of the active hand and fingertip forces of the opposite hand were recorded simultaneously. In the control group, slight mirror activity (or mirroring) was found that decreased with age. In participants with CP, mirror activity was 15 times stronger than in the control group, and was found at all age levels. Mirroring was more prominent in the unaffected hand of the CP group. The amount of mirror activity was not related to the degree of hemiplegia, which was assessed with measures of spasticity, strength, and dexterity. Mirror movements disturbed functional bimanual skills, although to some extent they could be suppressed by voluntary effort.

Gait analysis in idiopathic normal pressure hydrocephalus--which parameters respond to the CSF tap test?

OBJECTIVES: Normal pressure hydrocephalus (NPH) is an often underestimated cause of hypokinetic gait disorders in the elderly. Diagnosing NPH is a complex problem, since many symptoms overlap with other neurological diseases. The purpose of the present study was to characterize the gait pattern in NPH quantitatively. Additionally, we analyzed the improvement of gait parameters following tapping of cerebrospinal fluid (CSF). METHODS: Gait analysis was performed in 10 patients and 12 age-matched healthy controls during overground and treadmill locomotion. RESULTS: Compared to healthy controls, patients with NPH walked significantly slower, with shorter and more variable strides and a somewhat lower cadence. The feet were not lifted to a normal height and the dorsal extension of the forefoot prior to heel-strike was insufficient. Balance-related gait parameters such as step width and the foot rotation angles were significantly increased in NPH, while their variability was lower. Only some gait parameters improved after tapping 30 ml CSF. Gait velocity increased by about 23% due to an increased stride length, while the cadence remained unchanged. Balance-related gait parameters and the foot-to-floor clearance during swing were not affected by the treatment. CONCLUSIONS: In conclusion, we found a triad of decreased stride length, decreased foot-to-floor clearance and a broad-based gait to be the typical features of the gait abnormality in NPH. Only the stride length improved following a diagnostic spinal tap. These results may help to more reliably diagnose the condition of NPH in a routine clinical setting.

X-ray kinematic analysis of forelimb movements during target reaching and food taking in the cat.

We have used a three-dimensional X-ray cinematographic approach to investigate the kinematics of the forelimb during target reaching and food taking in five cats. Measurements of the trajectory of the limb during the reaching movement showed that the movement paths of the metacarpophalangeal joint (MCP) and the wrist were sigmoidal with a long nearly linear segment. The elbow followed a bent movement path with maximal inflection in the middle. The path of the humerus had an ascending parabola-like characteristic. The velocity profiles of the MCP and wrist were nearly bell-shaped and skewed to the left, whereas the profiles of the elbow joint were more or less double peaked with the second peak occurring 60-40 ms before object contact. Several different velocity peaks reflecting specific aspects of the task existed when the bell-shaped velocity profiles were divided in their vectorial components. Angular motion of the elbow consisted of a flexion-extension sequence during the reach and a flexion during the subsequent retraction. After an initial flexion during lift-off the wrist was extended. It kept this extended position during orienting towards the food container. During the retraction phase it was further extended. The angle between the wrist axis and the parasagittal plane changed during the movement. It first increased, then decreased during the last 100 ms before the object was reached. During the retraction it increased again to support the object weight against gravity. The position of the wrist was established by radio-ulnar supination and movements of the whole arm around the shoulder joint. We hypothesize that the position of the wrist axis is the controlled variable during protraction and retraction, regardless of whether it is achieved by radio-ulnar supination or by movements around the shoulder.

Analysis of gait in cervical myelopathy.

Gait disorders are a frequent symptom of cervical spondylotic myelopathy (CSM). Twelve patients with CSM underwent gait analysis before and after decompressive surgery. They were assessed on a walkway and a treadmill and compared with a healthy matched control group. The following features were observed in the CSM group before surgery: significantly reduced gait velocity and step length (P<0. 05), prolonged double support, increased step width, and reduced ankle joint extension during treadmill walking. Knee and hip kinematics did not differ from controls. Two months after surgery, spatio-temporal parameters had moved towards normal values, velocity, step length and cadence had increased significantly, and there was reduction of step width during treadmill walking, indicating improved equilibrium. Gait analysis is an objective tool to document functional recovery after decompressive surgery in CSM.

Prehension movements and motor development in children.

The maturation of manual dexterity and other sensorimotor functions was assessed with various behavioural tests. In healthy children (age 4-5 years) and in adults, the kinematics of reaching and grasping, a bimanual task and fast repetitive tapping movements were analysed. Furthermore a comprehensive motor function score (MOT), probing agility and balance, was evaluated. In the prehension task, the straightness of the reaching trajectories increased with age. Children opened their grip relatively wider than adults, thus grasping with a higher safety margin. The speed of both tapping and bimanual movements increased with age, and higher scores were reached in the MOT. Although the different behavioural tests sensitively indicated maturational changes, their results were generally not correlated, i.e. the outcome of a particular test could not predict the results of other tasks. Hence there is no simple and uniform relationship between different behavioural data describing maturation of sensorimotor functions.

X-ray kinematic analysis of shoulder movements during target reaching and food taking in the cat.

Co-ordinate movements around the shoulder are essential during reaching movements. We performed a quantitative kinematic analysis of movements of the shoulder girdle: three-dimensional X-ray frames (time resolution 20 ms) were recorded during the target-reaching and food-taking paradigm in five cats either sitting (n = 4) or standing (n = 1) in front of a food well. Movements of the scapula consisted of a flexion of the scapula (anteversion of the glenoid) followed by flexion of the gleno-humeral joint (decrease in the angle between the scapular spine and humerus). In the sitting animals, the gleno-humeral flexion reversed to extension some 120 ms before object contact, while in the standing animal flexion continued during the ongoing scapular flexion. In both cases, the scapula was nearly horizontal at the end of target reaching. The fulcrum for scapular movements was located near the vertebral border of the scapula at the medial elongation of the scapular spine. No major translational components of the fulcrum with respect to the trunk were found during reaching. Together with full flexion of the scapula, this reduces the number of degrees of freedom considerably and thereby probably simplifying the specification of the end-point of the limb chain. End-point specification is further supported by rotational movements of the scapula. In the sitting animal, the amplitude of inward rotation along the long axis of the scapula was around 20 degrees, while it was much more variable in the standing animal, reflecting more variable starting positions. We hypothesize that the glenoid is used to 'foveate' the target object.

Assessment of sensorimotor functions after traumatic brain injury (TBI) in childhood - Methodological aspects.

Various basic qualitative and quantitative methods for the evaluation of sensorimotor functions after Traumatic Brain Injury (TBI) are introduced and discussed. Methodological aspects are illustrated by a single case follow-up study of a child after severe TBI (age 11; 7–12;1 yrs; 6, 8 and 12 month post TBI) in comparison to an age-matched healthy control group (N=16). The evaluation consisted of neurological investigation, Barthel-Index, Terver Numeric Score for Functional Assessment, Rappaport Disability Rating Scale (modified version), a coordination-test for children (KTK), a pilot-tested Motor Function Score, quantitative evaluation of spatiotemporal gait parameters on a walkway and on a treadmill, and the kinematic assessment of hand motor functions. Quantitative movement analyses revealed two general types of motor disorder: Slowing of movements and compensatory motor strategies. Averaged z-scores showed deficits, which were pronounced in fine motor skills (hand movements: 1.86, gait: 1.3). During follow-up, a strong improvement rate during the first (-0.48 z-scores) and nearly no improvement rate (-0.03 z-scores) during the second time interval was seen. Clinical scores and developmental tests were not able to document the whole restitutional course, whereas motor tests with special emphasis on functional aspects and the quantitative movement assessment seemed to be suitable methods. We conclude that a sufficient evaluation of sensorimotor functions after TBI in childhood needs an increase in procedural uniformity on onehand and the combination of various qualitative and quantitative methods on the other hand. To connect both claims, further research is necessary.