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PubMed2003

[Development of a robotic walking simulator for gait rehabilitation].

Restoration of gait is a major concern of rehabilitation after stroke or spinal cord injury. Modern concepts of motor learning favour a task-specific repetitive approach, i.e. "whoever wants to learn to walk again must walk." However, the physical demands this places on the therapist, is a limiting factor in the clinical routine setting. This article describes a robotic walking simulator for gait training that enables wheelchair-bound subjects to freely carry out repetitive practicing of an individually adapted gait pattern under simulation of the manual guidance of an experienced therapist. The technical principle applied makes use of programmable footplates with permanent foot/machine contact in combination with compliance control. The solution chosen comprises a planar parallel-serial hybrid kinematic system with three degrees of freedom that moves the feet in the sagittal plane. Gait analysis while floor walking and stair climbing, clinical practicability and safety aspects were the basis for the design. A variable compliance control enables man-machine interaction, ranging from purely position controlled movement to full compliance during swing phase above a virtual ground profile. In full compliance mode the robotic walking simulator behaves like a haptic device. The concept presented offers new prospects for individualized gait rehabilitation.

Artificial Intelligence↗

PubMed2001

Locomotor therapy in neurorehabilitation.

Gait rehabilitation is a major aspect of neurological rehabilitation. This review is on locomotor therapy by treadmill stimulation with partial body weight support evolving as a very promising treatment concept over the last years. It enables severely affected patients the repetitive practice of complex gait cycles and thus follows modern aspects of motor learning favoring a task-specific approach. Several studies have shown its potential in patients after stroke, spinal cord injury, M. Parkinson and cerebral palsy. An electromechanical gait trainer relieving the strenuous effort of the therapists and controlling the trunk in a phase-dependent manner is a new alternative.

Adult↗

PubMed1989

[Psychological and neurologic long-term consequences of brain tumors in children. A pilot study].

Brain tumor is one of the most common forms of cancer in children. The therapy includes surgical interventions, radiation of the central nervous system and chemotherapy. Combining these methods of treatment has remarkably improved the survival of children with certain brain tumours (e.g. medulloblastoma). However, long-term studies have revealed serious psychological and somatic consequences of the disease and the treatment. This paper presents the results of a pilot study of nine children with brain tumor. The patients were examined using a battery of neuropsychological methods (Luria's Neuropsychological Investigation, WISC-R), a semi-structured interview (Child Assessment Schedule), a parent report form (Achenbach Child Behaviour Checklist) and a clinical neurological examination. The most striking finding from this investigation was in the psychosocial field. Except for one child, all the patients showed an introvert reaction pattern with a tendency towards anxiety, depression and social withdrawal. All the children showed some neurological and neuropsychological deficits. Except in the case of two mentally retarded children, cognitive functions were within the lower normal range. Specific learning, memory and fine-motor disabilities were found in more than half of the patients. The investigation suggested that both fine-motor and mental performance was detrimentally affected by increased speed. This seems to be an area of special interest for further studies.

Adolescent↗

PubMed2003

Task-specific internal models for kinematic transformations.

Numerous studies of motor learning have focused on how people adapt their reaching movements to novel dynamic and visuomotor perturbations that alter the actual or visually perceived motion of the hand. An important finding from this work is that learning of novel dynamics generalizes across different movement tasks. Thus adaptation to an unusual force field generalizes from center-out reaching movements to circular movements (Conditt et al. 1997). This suggests that subjects acquired an internal model of the dynamic environment that could be used to determine the motor commands needed for untrained movements. Using a task interference paradigm, we investigated whether transfer across tasks is also observed when learning visuomotor transformations. On day 1, all subjects adapted to a +30 degrees rotation while making center-out-and-back reaching movements. After a delay of 5 min, different groups of subjects then adapted to a -30 degrees rotation while performing either a continuous tracking task, a figure-eight drawing task, or the center-out-and-back reaching task. All subjects were then retested the next day on the +30 degrees rotation in the reaching task. As expected, subjects who experienced the opposing rotations while performing the same reaching tasks showed no retention of learning for the first rotation when tested on day 2 (Krakauer et al. 1999). In contrast, such retrograde interference was not observed in the two groups of subjects who experienced the opposing rotations while performing different tasks. In fact, their performance on day 2 was similar to that of control subjects who never experienced the opposite rotation. This lack of interference suggests that memory resources for visuomotor rotations are task specific.

Adult↗

PubMed1991

Application of motor learning principles in occupational therapy.

The processes underlying skill acquisition depend on the nature of the task and the stage of the learner. In addition, feedback and practice are two potent learning variables when used appropriately in the instruction of motor tasks. Occupational therapists involved in the training and retraining of motor skills can benefit from knowledge of instructional methods used by coaches and physical educators. This paper reviews commonly accepted principles of motor learning and applies these principles to occupational therapy treatment. The stage of the learner, type of task, feedback, practice, and facilitation of skill acquisition are emphasized. Specific examples of how occupational therapists can use motor learning principles in treatment are given.

Biofeedback, Psychology↗

PubMed2002

Subliminal words activate semantic categories (not automated motor responses).

Semantic priming by visually masked, unidentifiable ("subliminal") words occurs robustly when the words appearing as masked primes have been classified earlier in practice as visible targets. It has been argued (Damian, 2001) that practice enables robust subliminal priming by automatizing learned associations between words and the specific motor responses used to classify them. Two experiments demonstrate that, instead, the associations formed in practice that underlie subliminal priming are between words and semantic categories. Visible words classified as pleasant or unpleasant in practice with one set of response key assignments functioned later as subliminal primes with appropriate valence, even when associations of keys with valences were reversed before the test. This result shows that subliminal priming involves unconscious categorization of the prime, rather than just the automatic activation of a practiced stimulus-response mapping.

Automatism↗

PubMed2005

Specific neurodevelopmental damage in mice offspring following maternal inflammation during pregnancy.

Intrauterine inflammation is a major risk for offspring neurodevelopmental brain damage and may result in cognitive limitations and poor cognitive and perceptual outcomes. Pro-inflammatory cytokines, stimulated during inflammatory response, have a pleotrophic effect on neurons and glia cells. They act in a dose-dependent manner, activate cell-death pathways and also act as trophic factors. In the present study, we have examined in mice the effect of short, systemic maternal inflammation on fetal brain development. Maternal inflammation, induced by lipopolysaccharide (LPS) at gestation day 17, did not affect morphogenic parameters and reflex development during the first month of life. However, maternal inflammation specifically increased the number of pyramidal and granular cells in the hippocampus, as well as the shrinkage of pyramidal cells, but not of the granular cells. No additional major morphological differences were observed in the cerebral cortex or cerebellum. In accordance with the morphological effects, maternal inflammation specifically impaired distinct forms of learning and memory, but not motor function or exploration in the adult offspring. The specific deficiency observed, following maternal inflammation, may suggest particular sensitivity of the hippocampus and other associated brain regions to inflammatory factors during late embryonic development.

Age Factors↗

PubMed1999

Simulations of cerebellar motor learning: computational analysis of plasticity at the mossy fiber to deep nucleus synapse.

We question the widely accepted assumption that a molecular mechanism for long-term expression of synaptic plasticity is sufficient to explain the persistence of memories. Instead, we show that learning and memory require that these cellular mechanisms be correctly integrated within the architecture of the neural circuit. To illustrate this general conclusion, our studies are based on the well characterized synaptic organization of the cerebellum and its relationship to a simple form of motor learning. Using computer simulations of cerebellar-mediated eyelid conditioning, we examine the ability of three forms of plasticity at mossy fiber synapses in the cerebellar nucleus to contribute to learning and memory storage. Results suggest that when the simulation is exposed to reasonable patterns of "background" cerebellar activity, only one of these three rules allows for the retention of memories. When plasticity at the mossy fiber synapse is controlled by nucleus or climbing fiber activity, the circuit is unable to retain memories because of interactions within the network that produce spontaneous drift of synaptic strength. In contrast, a plasticity rule controlled by the activity of the Purkinje cell allows for a memory trace that is resistant to ongoing activity in the circuit. These results suggest specific constraints for theories of cerebellar motor learning and have general implications regarding the mechanisms that may contribute to the persistence of memories.

Cerebellar Cortex↗

PubMed2001

Time course and temporal order of changes in movement kinematics during motor learning: effect of joint and instruction.

Learning a motor task is associated with specific changes in movement kinematics. Recently, it has been shown that changes in different kinematic parameters occurred with different time courses for subjects who practiced simple, single-joint elbow movements. For example, movement time was seen to decrease and level off in a shorter time than peak velocity, which increased and plateaued later. What is not known, however, is whether the time course and temporal order of these learning-related changes seen at the elbow are similar for movements learned at other joints and with different instructions. In this study, neurologically normal subjects practiced 50 degrees -flexion movements made at the wrist, with the instruction to be both "fast and accurate" (same instruction used in the earlier elbow study). A different group of subjects practiced wrist movements of the same amplitude, but with instructions to make movements that were "always accurate;" only as movement skill developed could subjects increase their speed (but without ever sacrificing accuracy). We measured time-related parameters (duration of acceleration, duration of deceleration, and total movement duration) and magnitude-related parameters (peak velocity, peak acceleration, and peak deceleration). We found that the time course of changes in kinematic parameters for subjects instructed to be "fast and accurate" was similar to that reported at the elbow. When the instruction was changed to be "always accurate," the time for changes in kinematic parameters to level off was found to be longer. However, regardless of instruction, time-related parameters plateaued before magnitude-related parameters. Thus, our results indicate that motor learning mechanisms may operate in a similar way at different joints.

Adult↗

PubMed2003

The Montréal Rehabilitation Performance Profile: a statistical model for assessing stair descent in children with cognitive impairments.

OBJECTIVES: To characterize the responsiveness of the Montréal Rehabilitation Performance Profile (MRPP); to measure the differential effectiveness of a task-specific (TS) and a task-nonspecific (TNS) motor learning format to promote alternating stair descent in children with cognitive impairments; and to evaluate the relevance of the MRPP to evidence-based practice. DESIGN: Randomized comparison of 2 age-matched groups; psychometric testing of measurement tool. SETTING: School for children with developmental and cognitive impairments. PARTICIPANTS: Ambulatory sample of convenience: 18 children, age 5 to 9 years, with moderate to severe cognitive impairment. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The MRPP variables measured at baseline; end of 10-week intervention; and 5 and 10 weeks postintervention. Analysis of variance for repeated measures and part-whole correlation. RESULTS: Global stair descent performance improved for both TS and TNS groups over time (P=.001). However, a specific acquisition and retention of the alternating pattern of descent was associated with the TS format. CONCLUSION: The MRPP was responsive to small differences in stair descent performance that are specific to the format of the motor learning intervention. The MRPP allows clinicians to determine the timing of the intervention needed to maintain or improve stair descent ability.

Analysis of Variance↗

PubMed2003

Alterations in brain protein kinase C isoforms following developmental exposure to a polychlorinated biphenyl mixture.

PCBs have been shown to alter several neurochemical end-points and are implicated in the etiology of some neurological diseases. Recent in vivo studies from our laboratory indicated that developmental exposure to a commercial PCB mixture, Aroclor 1254, caused perturbations in calcium homeostasis and changes in protein kinase C (PKC) activities in rat brain. However, it is not known which molecular substances are targets for PCB-induced developmental neurotoxicity. Since the PKC signaling pathway has been implicated in the modulation of motor behavior as well as learning and memory, and the roles of PKC are subspecies specific, the present study attempted to analyze the effects on selected PKC isozymes in the cerebellum and the hippocampus following developmental exposure (gestational day 6 through postnatal day 21) to a PCB mixture, Aroclor 1254. The results indicated that the developmental exposure to PCBs caused significant hypothyroxinemia and age-dependent alterations in the translocation of PKC isozymes; the effects were greatly significant at postnatal day (PND) 14. Immunoblot analysis of PKC-alpha (alpha) from both cerebellum and hippocampus revealed that developmental exposure to Aroclor 1254 caused a significant decrease in cytosolic fraction and an increase in particulate fraction. There was no significant difference between these two brain regions on the level of fractional changes. However, the ratio between the fractions (particulate/cytosol) from cerebellum only was increased in a dose-dependent manner. Analysis of PKC-gamma (gamma) in cerebellum on PND14 showed a decrease in cytosolic fraction in both dose groups and an increase in particulate fraction at high dose (6 mg/kg) only. The ratio between the two fractions was increased in a dose-dependent manner. In the hippocampus, there was a significant decrease in PKC-gamma in cytosolic fraction of the high-dose group and a significant increase in particulate fraction of the low-dose group. But, the ratio between the fractions showed a significant increase (2.6-fold increase in high dose on PND14). Analysis of PKC-epsilon (epsilon) in cerebellum showed a significant decrease in cytosolic fraction at PND14, while particulate PKand an increase in ratio between fractions at 6 mg/kg on PND14. The results from this study indicate that the patterns of subcellular distributions of PKC isoforms following a developmental PCB exposure were PKC isozyme- and developmental stage-specific. Considering the significant role of PKC signaling in motor behavior, learning and memory, it is suggested that altered subcellular distribution of PKC isoforms at critical periods of brain development may be a possible mechanism of PCB-induced neurotoxic effects and that PKC-alpha, gamma, and epsilon may be among the target molecules implicated with PCB-induced neurological impairments during developmental exposure. It is believed that this is the first report successfully identifying PKC isoforms responding to PCBs during developmental exposure.

Aging↗

PubMed2005

Instructive signals for motor learning from visual cortical area MT.

Sensory error signals have long been proposed to act as instructive signals to guide motor learning. Here we have exploited the temporal specificity of learning in smooth pursuit eye movements and the well-defined anatomical structure of the neural circuit for pursuit to identify a part of sensory cortex that provides instructive signals for motor learning in monkeys. We show that electrical microstimulation in the motion-sensitive middle temporal area (MT) of extrastriate visual cortex instructs learning in smooth eye movements in a way that closely mimics the learning instructed by real visual motion. We conclude that MT provides instructive signals for motor learning in smooth pursuit eye movements under natural conditions, suggesting a similar role for sensory cortices in many kinds of learned behaviors.

Action Potentials↗

PubMed2001

Long-term adaptation to dynamics of reaching movements: a PET study.

Positron emission tomography (PET) was used to examine changes in the cerebellum as subjects learned to make movements with their right arm while holding the handle of a robot that produced a force field. Brain images were acquired during learning and then during recall at 2 and 4 weeks. We also acquired images during a control task where the force field was not learnable and subjects did not show any improvements across sessions. During the 1st day, we observed that motor errors decreased from the control condition to the learning condition. However, regional cerebral blood flow (rCBF) in the posterior region of the right cerebellar cortex initially increased from the control condition and then gradually declined with reductions in motor error. Correspondingly, rCBF in the ipsilateral deep cerebellar nuclei (DCN) initially decreased from the control condition and then increased with reductions in motor error. If measures of rCBF mainly reflect presynaptic activity of neurons, this result predicts that DCN neurons fire with a pattern that starts high in the control task then decreases as learning proceeds. Similarly, Purkinje cells should generally have their lowest activity in the control task. This pattern is consistent with neurophysiological recordings that find that cerebellar activity during early learning of a motor task may mainly reflect changes in coactivation of muscles of the limbs, rather than a learning specific signal. By the end of the first session, motor errors had reached a minimum and no further improvements were observed. However, across the weeks a region in the anterior cerebellar cortex showed gradual decreases in rCBF that could not be attributed to changes in motor performance. Because patterns of rCBF in the cortex and nuclei were highly anti-correlated, we used structural equation modeling to estimate how synaptic activity in the cerebellar cortex influenced synaptic activity in the DCN. We found a negative correlation with a strength that significantly increased during the 4 weeks. This suggests that, during long-term recall, the same input to the cerebellar cortex would produce less synaptic activity at the DCN, possibly because of reduced cerebellar cortex output to the DCN.

Adaptation, Biological↗

PubMed2006

Cortical motor areas are activated early in a characteristic sequence during post-movement processing.

During motor learning in goal-directed reactions, a specific movement has to be associated with feedback about the movement's success. Such feedback often follows when the movement is already over. We investigated the time-course of post-movement cortical motor processing by high-resolution analysis of lateralized post-movement potentials in forewarned and simple reaction time tasks. In both paradigms we could separate a post-movement component (motor postimperative negative variation-mPINV) peaking about 500 ms after the button press (confirmed by electromyogram and accelerometer). mPINV could not be sufficiently explained by motor cortex activity related to EMG output and/or by sensory feedback. mPINV was enhanced by long intertrial intervals and its lateralization changed with response movement side. Its scalp potential distribution resembled (pre-)motor cortex activity during preceding movement stages and differed from the frontal motor potential peak (proprioceptive and somatosensory reafferent feedback); suggesting post-movement activation of pre-/primary motor cortex. Dipole source analysis yielded a single radial source near premotor cortex which explained lateralized mPINV almost completely. mPINV was present in simple reaction time tasks, indicating that mPINV is an independent component and does not represent delayed resolution of pre-movement negativity. An equivalent of "classical" PINV (cPINV) occurred later over prefrontal and anterior temporal sites in simple and forewarned reaction time tasks. Our results suggest that high-resolution analysis of lateralized movement-related potentials allows to image post-movement motor cortex activity and might provide insights into basic mechanisms of motor learning: A characteristic sequence might involve motor cortex activation (mPINV) before "higher order associative areas" come into play (cPINV).

Adult↗

PubMed2002

Changes of cortico-striatal effective connectivity during visuomotor learning.

It has been suggested that the cortico-striatal system might play a crucial role in learning behavioural plans of action. We have tested this hypothesis by studying the dynamics of functional coupling among the neural elements of cortico-striatal circuitry. Human cerebral activity was measured with functional magnetic resonance imaging (fMRI) during the learning of an associative visuomotor task. Structural equation modelling of regional fMRI time-series was used to characterize learning-related changes in effective connectivity. We report that learning to associate visual instructions with motor responses significantly altered cortico-striatal functional couplings. Specific learning-related increases of effective connectivity were found in temporo-striatal and fronto-striatal circuits. Connectivity among portions of the frontal cortex decreased as a function of learning. Temporo-frontal and parieto-frontal couplings were not altered during learning. We infer that novel visuomotor associations are established through the enhancement of specific cortico-striatal circuits, rather than through the alteration of direct temporo-frontal or parieto-frontal connectivity.

Cerebral Cortex↗

PubMed1993

Mild Brachmann-de Lange syndrome. Phenotypic and developmental characteristics of mildly affected individuals.

Since 1981, we have identified 3 patients with mild Brachmann-de Lange syndrome (BDLS) who have had subtle but definite manifestations of the syndrome and mild effects on growth and development. J.G. (B.D. 12/9/72) was first examined at 20 months. He had rather typical craniofacial findings and hirsutism, limitation of full supination of his arms, and brachyclinodactyly of the 5th fingers. IQ was estimated at 65. K.H. (B.D. 10/10/83) was first examined by us at age 9 months and was diagnosed as having "mild" BDLS. At age 5, K.H. has demonstrated relatively normal cognitive development (low average-average IQ of 74) with specific learning problems: weakness of visual-motor skills, delayed expressive language development, and articulation difficulties. At age 7, he was attending a regular 1st grade classroom, with some special education assistance. M.E. (B.D. 4/19/78) was diagnosed at age 10 years as having "mild" BDLS. His physical changes were more subtle than those of the 2 patients above. At age 10, M.E. was in the regular 4th grade classroom receiving special education support. His IQ was in the borderline-low-average range. He had strengths in rote verbal skills, with weaknesses in reading and writing. These 3 patients demonstrate mild BDLS in which characteristic manifestations of the syndrome, particularly craniofacial anomalies, are present and recognizable, but quite subtle, thus making the clinical diagnosis difficult. In addition, the milder physical phenotype is associated with milder cognitive and behavioral consequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed2007

Maternal behavior, infant development, and the question of developmental resources.

The natural development of maternal and infant behavior occurs in a dyad characterized by synchrony and reciprocal interactions. Major concepts used to describe and analyze this synchrony were reviewed. It was concluded that the dyad undergoes a developmental progression in which each part of the dyad is both a developing organism and a reliably changing milieu forming part of the extended inheritance of the other. The reliability of inherited resources is rooted in interactions essential to life, such as those used to transfer metabolic needs to dependent offspring; to stimulation (incidentally but necessarily) associated with life-supporting mechanisms; and to perceptual, motor, or learning mechanisms used to extract specific resources from the available milieu. The diverse resources in extended inheritance contribute to the construction of new traits through opportunistic shaping or regulating interactions among them that are unrestricted by their function at earlier stages.

Animals↗

PubMed2005

How does transcranial DC stimulation of the primary motor cortex alter regional neuronal activity in the human brain?

Transcranial direct current stimulation (tDCS) of the primary motor hand area (M1) can produce lasting polarity-specific effects on corticospinal excitability and motor learning in humans. In 16 healthy volunteers, O positron emission tomography (PET) of regional cerebral blood flow (rCBF) at rest and during finger movements was used to map lasting changes in regional synaptic activity following 10 min of tDCS (+/-1 mA). Bipolar tDCS was given through electrodes placed over the left M1 and right frontopolar cortex. Eight subjects received anodal or cathodal tDCS of the left M1, respectively. When compared to sham tDCS, anodal and cathodal tDCS induced widespread increases and decreases in rCBF in cortical and subcortical areas. These changes in rCBF were of the same magnitude as task-related rCBF changes during finger movements and remained stable throughout the 50-min period of PET scanning. Relative increases in rCBF after real tDCS compared to sham tDCS were found in the left M1, right frontal pole, right primary sensorimotor cortex and posterior brain regions irrespective of polarity. With the exception of some posterior and ventral areas, anodal tDCS increased rCBF in many cortical and subcortical regions compared to cathodal tDCS. Only the left dorsal premotor cortex demonstrated an increase in movement related activity after cathodal tDCS, however, modest compared with the relatively strong movement-independent effects of tDCS. Otherwise, movement related activity was unaffected by tDCS. Our results indicate that tDCS is an effective means of provoking sustained and widespread changes in regional neuronal activity. The extensive spatial and temporal effects of tDCS need to be taken into account when tDCS is used to modify brain function.

Adult↗