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PubMedDate not supplied

Habit and skill learning in schizophrenia: evidence of normal striatal processing with abnormal cortical input.

Different forms of nondeclarative learning involve regionally specific striatal circuits. The motor circuit (involving the putamen) has been associated with motor-skill learning and the dorsolateral prefrontal cortex (DLPFC) circuit (involving the caudate) has been associated with cognitive-habit learning. Efforts to differentiate functional striatal circuits within patient samples have been limited. Previous studies have provided mixed results regarding striatal-dependent nondeclarative learning deficits in patients with schizophrenia. In this study, a cognitive-habit learning task (probabilistic weather prediction) was used to assess the DLPFC circuit and a motor-skill learning task (pursuit rotor) was used to assess the motor circuit in 35 patients with schizophrenia and 35 normal controls. Patients with schizophrenia displayed significant performance differences from controls on both nondeclarative tasks; however, cognitive-habit learning rate in patients did not differ from controls. There were performance and learning-rate differences on the motor-skill learning task between the whole sample of patients and controls, however, analysis of a subset of patients and controls matched on general intellectual level eliminated learning rate differences between groups. The abnormal performance offset between patients with schizophrenia and controls in the absence of learning rate differences suggests that abnormal cortical processing provides altered input to normal striatal circuitry.

Adult↗

PubMed1997

The Specificity of Motor Skill and Manual Asymmetry: A Review of the Evidence and Its Implications.

Results of investigations on gaining control of limb movements are reviewed, and their contribution to understanding the development of manual asymmetries is discussed in relation to the discrimination and programming of appropriate neuromuscular resources. An examination of the relevant evidence on number and types of manual asymmetries recorded provides strong grounds for concluding that where asymmetries occur, they simply represent a further example of the well-documented activity-specific nature of motor skills and of the extremely lengthy periods of learning or experience needed for their acquisition and perfection. This specificity of motor skill and manual asymmetry also readily accounts for most of the discrepancy usually reported between assessments of hand preference and performance differences between hands, because these alternative measures of handedness have rarely employed the same range or variety of tasks.

handedness↗

PubMed2003

Poststroke motor dysfunction and spasticity: novel pharmacological and physical treatment strategies.

Following stroke, approximately 90% of patients experience persistent neurological motor deficits that lead to disability and handicap. Both pharmacological and physical treatment strategies for motor rehabilitation may be considered. In terms of pharmacological treatment, drugs that may potentially promote motor recovery when added to a regimen of physical therapy include the stimulants amphetamine and methylphenidate, as well as levodopa and fluoxetine. Botulinum toxin A has proven effective and well tolerated in several placebo-controlled trials for the treatment of focal upper and lower limb spasticity, although it has not been shown to improve motor function. The focal injection of botulinum toxin A inhibits the release of acetylcholine into the synaptic cleft, resulting in a reversible paresis of the muscles relevant for the spastic deformity. Other drugs, such as benzodiazepines, antiepileptic drugs and antipsychotics, may have detrimental effects on motor function and should be avoided, if possible. With respect to physical strategies, modern concepts of motor learning favour a task-specific repetitive approach that induces skill-acquisition relevant to the patient's daily life. Constrained-induced movement therapy based on the concept of learned non-use, electromyography-triggered electrical stimulation of the wrist muscles, robot-assisted motor rehabilitation to increase therapy intensity and bilateral practice to facilitate the movement of the paretic extremity are examples in upper limb rehabilitation. Lower limb rehabilitation has been enriched by treadmill training with partial bodyweight support, enabling the practice of up to 1000 steps per session; automated gait rehabilitation to relieve the strenuous effort required of the therapist; and rhythmic auditory stimulation, applying individually adjusted music to improve walking speed and symmetry.

Animals↗

PubMed1992

Alternating actual and imagery practice: preliminary theoretical considerations.

The main purpose of the following experiments was to reexamine the acquisition effects of alternating actual and imagery practice on retention. This was accomplished by making retention comparisons between groups that either alternated actual and imagery practice, alternated actual practice and rest, employed all actual or all imagery practice, or performed an unrelated task (the control) during acquisition. Results from Experiment 1 indicated that the actual practice and the alternating actual and imagery practice groups produced equivalent scores that were greater than the equivalent scores of the imagery practice and alternating actual practice and rest groups. All experimental groups performed better than the control. Because the retention test was identical to the actual practice protocol, practice specificity may have biased the retention relative standings in favor of the actual practice group. Experiment 2 was identical to Experiment 1 except subjects were transferred to a contralateral limb retention test. Results indicated that the alternating actual and imagery practice group produced better retention scores than the equivalent retention scores of the actual practice and imagery practice groups. These three groups produced higher retention scores than the alternating actual practice and rest group, which was better than the control. These results support the notion that alternating actual and imagery practice facilitates motor learning and suggest that practice specificity may be a factor in response imagery experiments. Based on the notion that actual and imagery practice activate shared and unique mechanisms, several hypotheses were offered to explain these results.

Adult↗

PubMed1978

The effect of rest following massed practice of continuous and discrete motor tasks.

Theories of the rest-related phenomena of reminiscence and warm-up decrement regard them as independent, being due to different factors. In this study it was found that rest following massed practice of a continuous task increased performance (reminiscence) and rest following massed practice of a discrete task lowered performance (warm-up decrement). The near-zero correlation found between the phenomena indicates that they are indeed independent and task-specific. Implications of the findings for the prediction of the effect of rest, and the fact that much motor learning and performance is task-specific, is discussed.

Journal Article↗

PubMed2004

Cerebellar stroke impairs temporal but not spatial accuracy during implicit motor learning.

OBJECTIVE: Numerous studies have demonstrated cerebellar activity during implicit motor learning, but few have addressed its specific role. The purpose of this study was to determine if specific components (spatial or temporal) of an implicit motor-tracking task were affected by cerebellar stroke. METHODS: The authors studied the performance of individuals with unilateral cerebellar stroke (n = 7)and a control group (n = 10) across 3 acquisition days and at a delayed retention test as they practiced a unimanual tracking task with the contralesional upper extremity. RESULTS: After cerebellar stroke, participants demonstrated reduced tracking errors for repeating sequences compared to random sequences; however, decomposition of tracking performance into temporal and spatial components revealed persistent deficits in tracking time lag despite improved spatial accuracy. A lesion analysis showed that the dentate nucleus was the only common region affected by all cerebellar strokes. CONCLUSIONS: During implicit motor learning, the cerebellum appears to participate in the formation of predictive strategies for the timing of motor responses, rather than for the accuracy of motor execution. Because deficits were found in the contralesional upper extremity, the authors suggest that this function is not lateralized to 1 hemisphere; cerebellar output may affect the formation of an internal model for timing movements in both upper extremities.

Adult↗

PubMed1987

Quality of life in children with primitive neuroectodermal tumors (medulloblastoma) of the posterior fossa.

We reviewed our experience in 43 consecutive patients with primitive neuroectodermal tumors (medulloblastoma), PNET (MB), treated between 1975 and 1984, to characterize their quality of life and identify factors which impacted on long-term function. Twenty-four of forty-three (56%) of children are alive and free of disease, a median of 4.5 years after diagnosis. The quality of life was analyzed for the 24 long-term survivors. 79% (19 of 24) were functioning well in everyday activities. The median full-scale intelligence quotient (FSIQ), obtained a median of 3.5 years after diagnosis for those tested (n = 17) was 97, with all but 3 (12%) of the patients functioning in the normal range. Specific learning, memory and fine-motor disabilities were found in over one half of patients. Factors associated with poorer performance and lower FSIQ included preoperative obtundation, the need for a permanent shunt, younger age at diagnosis, and a complicated postoperative course. It is concluded that (1) the majority of long-term survivors have 'normal' intellectual function, but may have specific intellectual and academic disabilities, and (2) preoperative and postoperative factors strongly impact on the quality of life of survivors.

Adolescent↗

PubMed2006

Functional imaging of sequence learning in Parkinson's disease.

Sequence learning, a cognitive task linked to cortico-striatal function, is impaired in Parkinson's disease (PD). We chose this task as a behavioral paradigm to study the functional architecture of PD in treated and untreated conditions. In our studies, participants were scanned with H(2)(15)O while performing a kinematically controlled motor sequence learning task and a matching motor baseline task. Experiments revealed that a specific sequence learning network predicts learning in normal subjects, and in independent cohorts of early and advanced PD patients. The analysis of the relationship of network activity to learning performance revealed diverging influences of dopaminergic therapy and deep brain stimulation (DBS). DBS of the internal GP and of STN increased network activity and task performance, while levodopa decreased both measures. In separate studies, we investigated the role of dopaminergic modulation on brain activation during sequence learning. In healthy subjects dopamine transporter (DAT) binding correlated with learning-related brain activation in prefrontal, premotor and cingulate cortices, and in the thalamus. By contrast, in PD most of these regional relationships were lost. Only ventral and dorsolateral prefrontal cortex activation correlated with caudate dopaminergic input. In a final set of studies, we found a significant decline in learning performance in early stage PD patients followed over the course of 2 years. Longitudinal declines in learning-related activation were found in parietal areas, while concomitant increases were localized to the left hippocampus. These observations support hypotheses on disease-stage and task-specific effects within the different cortico-striato-pallido-thalamocortical loops and the mesocortical system in PD.

Aged↗

PubMed2005

Neuropsychological deficits associated with driving performance in Parkinson's and Alzheimer's disease.

Neuropsychological and motor deficits in Parkinson's disease that may contribute to driving impairment were examined in a cohort study comparing patients with Parkinson's disease (PD) to patients with Alzheimer's disease (AD) and to healthy elderly controls. Nondemented individuals with Parkinson's disease [Hoehn & Yahr (H&Y) stage I-III], patients with Alzheimer's disease [Clinical Demetia Rating scale (CDR) range 0-1], and elderly controls, who were actively driving, completed a neuropsychological battery and a standardized road test administered by a professional driving instructor. On-road driving ability was rated on number of driving errors and a global rating of safe, marginal, or unsafe. Overall, Alzheimer's patients were more impaired drivers than Parkinson's patients. Parkinson's patients distinguished themselves from other drivers by a head-turning deficiency. Drivers with neuropsychological impairment were more likely to be unsafe drivers in both disease groups compared to controls. Compared to controls, unsafe drivers with Alzheimer's disease were impaired across all neuropsychological measures except finger tapping. Driving performance in Parkinson's patients was related to disease severity (H&Y), neuropsychological measures [Rey Osterreith Complex Figure (ROCF), Trails B, Hopkins Verbal List Learning Test (HVLT)-delay], and specific motor symptoms (axial rigidity, postural instability), but not to the Unified Parkinson Disease Rating Scale (UPDRS) motor score. Multifactorial measures (ROCF, Trails B) were useful in distinguishing safe from unsafe drivers in both patient groups.

Accidents, Traffic↗

PubMed2005

Learning and transfer of bimanual multifrequency patterns: effector-independent and effector-specific levels of movement representation.

Current behavioural theories consider that during motor learning, an effector-independent memory representation of the acquired skill is built up. Using a transfer paradigm, we addressed the nature of the memory representation for a 2:1 multifrequency co-ordination task, requiring, for example, the left arm to cycle twice as fast as the right. After learning this 2:1 pattern, transfer to its converse pattern (i.e., the right arm cycles twice as fast as the left) revealed powerful evidence for negative transfer. The converse task arrangement revealed similar effects. These observations suggest a reconsideration of current viewpoints on movement representations, which emphasize effector independence. Based on the present findings, we propose a new model of motor memory, consisting of an abstract, effector-independent and an effector-specific layer. The abstract code is hypothesized to represent general spatiotemporal movement features, whereas the specific representation refers to effector-related movement commands. This concept is consistent with recent neuroscientific evidence in animal and human species, and invites a reconsideration of current behavioural theories of motor learning and memory.

Adult↗

PubMed2000

Coincident activation of NMDA and dopamine D1 receptors within the nucleus accumbens core is required for appetitive instrumental learning.

The nucleus accumbens, a brain structure ideally situated to act as an interface between corticolimbic information-processing regions and motor output systems, is well known to subserve behaviors governed by natural reinforcers. In the accumbens core, glutamatergic input from its corticolimbic afferents and dopaminergic input from the ventral tegmental area converge onto common dendrites of the medium spiny neurons that populate the accumbens. We have previously found that blockade of NMDA receptors in the core with the antagonist 2-amino-5-phosphonopentanoic acid (AP-5; 5 nmol) abolishes acquisition but not performance of an appetitive instrumental learning task (Kelley et al., 1997). Because it is currently hypothesized that concurrent dopamine D(1) and glutamate receptor activation is required for long-term changes associated with plasticity, we wished to examine whether the dopamine system in the accumbens core modulates learning via NMDA receptors. Co-infusion of low doses of the D(1) receptor antagonist SCH-23390 (0.3 nmol) and AP-5 (0.5 nmol) into the accumbens core strongly impaired acquisition of instrumental learning (lever pressing for food), whereas when infused separately, these low doses had no effect. Infusion of the combined low doses had no effect on indices of feeding and motor activity, suggesting a specific effect on learning. We hypothesize that co-activation of NMDA and D(1) receptors in the nucleus accumbens core is a key process for acquisition of appetitive instrumental learning. Such an interaction is likely to promote intracellular events and gene regulation necessary for synaptic plasticity and is supported by a number of cellular models.

2-Amino-5-phosphonovalerate↗

PubMed2002

Learning of sequences of finger movements and timing: frontal lobe and action-oriented representation.

Motor sequence learning involves learning of a sequence of effectors with which to execute a series of movements and learning of a sequence of timings at which to execute the movements. In this study, we have segregated the neural correlates of the two learning mechanisms. Moreover, we have found an interaction between the two learning mechanisms in the frontal areas, which we claim as suggesting action-oriented coding in the frontal lobe. We used positron emission tomography and compared three learning conditions with a visuo-motor control condition. In two learning conditions, the subjects learned either a sequence of finger movements with random timing or a sequence of timing with random use of fingers. In the third condition the subjects learned to execute a sequence of specific finger movements at specific timing; we argue that it was only in this condition that the motor sequence was coded as an action-oriented representation. By looking for condition by session interactions (learning vs. control conditions over sessions), we have removed nonspecific time effects and identified areas that showed a learning-related increment of activation during learning. Learning of a finger sequence was associated with an increment of activation in the right intraparietal sulcus region and medial parietal cortex, whereas learning of a timing sequence was associated with an increment of activation in the lateral cerebellum, suggesting separate mechanisms for learning effector and temporal sequences. The left intraparietal sulcus region showed an increment of activation in learning of both finger and timing sequences, suggesting an overlap between the two learning mechanisms. We also found that the mid-dorsolateral prefrontal cortex, together with the medial and lateral premotor areas, became increasingly active when subjects learned a sequence that specified both fingers and timing, that is, when subjects were able to prepare specific motor action. These areas were not active when subjects learned a sequence that specified fingers or timing alone, that is, when subjects were still dependent on external stimuli as to the timing or fingers with which to execute the movements. Frontal areas may integrate the effector and temporal information of a motor sequence and implement an action-oriented representation so as to perform a motor sequence accurately and quickly. We also found that the mid-dorsolateral prefrontal cortex was distinguished from the ventrolateral prefrontal cortex and anterior fronto-polar cortex, which showed sustained activity throughout learning sessions and did not show either an increment or decrement of activation.

Adult↗

PubMed2005

SOX2 anophthalmia syndrome.

Heterozygous, de novo, loss-of-function mutations in SOX2 have been shown to cause bilateral anophthalmia. Here we provide a detailed description of the clinical features associated with SOX2 mutations in the five individuals with reported mutations and four newly identified cases (including the first reported SOX2 missense mutation). The SOX2-associated ocular malformations are variable in type, but most often bilateral and severe. Of the nine patients, six had bilateral anophthalmia and two had anophthalmia with contralateral microphthalmia with sclerocornea. The remaining case had anophthalmia with contralateral microphthalmia, posterior cortical cataract and a dysplastic optic disc, and was the only patient to have measurable visual acuity. The relatively consistent extraocular phenotype observed includes: learning disability, seizures, brain malformation, specific motor abnormalities, male genital tract malformations, mild facial dysmorphism, and postnatal growth failure. Identifying SOX2 mutations from large cohorts of patients with structural eye defects has delineated a new, clinically-recognizable, multisystem disorder and has provided important insight into the developmental pathways critical for morphogenesis of the eye, brain, and male genital tract.

Adolescent↗

PubMed2005

Supervised learning of postural tasks in patients with poststroke hemiparesis, Parkinson's disease or cerebellar ataxia.

Supervised learning of different postural tasks in patients with lesions of the motor cortex or pyramidal system (poststroke hemiparesis: 20 patients), nigro-striatal system (Parkinson's disease: 33 patients) and cerebellum (spinocerebellar ataxia: 37 patients) was studied. A control group consisted of 13 healthy subjects. The subjects stood on a force platform and were trained to change the position of the center of pressure (CP) presented as a cursor on a monitor screen in front of the patient. Subjects were instructed to align the CP with the target and then move the target by shifting the CP in the indicated direction. Two different tasks were used. In "Balls", the target (a ball) position varied randomly, so the subject learned a general strategy of voluntary CP control. In "Bricks", the subject had to always move the target in a single direction (downward) from the top to the bottom of the screen, so that a precise postural coordination had to be learned. The training consisted of 10 sessions for each task. The number of correctly performed trials for a session (2 min for each task) was scored. The voluntary control of the CP position was initially impaired in all groups of patients in both tasks. In "Balls", there were no differences between the groups of the patients on the first day. The learning course was somewhat better in hemiparetic patients than in the other groups. In "Bricks", the initial deficit was greater in the groups of parkinsonian and cerebellar patients than in hemiparetic patients. However, learning was more efficient in parkinsonian than in hemiparetic and cerebellar patients. After 10 days of training, the hemiparetic and cerebellar patients completed the acquisition at a certain level whereas the parkinsonian patients showed the ability for further improvement. The results suggest that motor cortex, cerebellum, and basal ganglia are involved in voluntary control of posture and learning different postural tasks. However, these structures play different roles in postural control and learning: basal ganglia are mainly involved in learning a general strategy of CP control while the function of the motor cortex chiefly concerns learning a specific CP trajectory. The cerebellum is involved in both kinds of learning.

Adult↗

PubMed2001

Body weight-supported treadmill training after stroke.

Gait rehabilitation is a major aspect of neurologic rehabilitation. This review focuses on locomotor therapy by treadmill stimulation with partial body weight support (BWS), which has become a very promising treatment concept over the past few years. It enables severely affected patients to follow modern aspects of motor learning, favoring a task-specific approach. Initially two therapists assist the movement, placing the paretic limbs and controlling the trunk movements. As compared with overground walking, patients walked more symmetrically, less spastically, and more efficiently on the treadmill with BWS. Several clinical controlled studies have shown its potential in patients after stroke, who regained walking ability faster in the acute or in the chronic stage. Controlled multicenter trials comparing locomotor and conventional therapy will be the next step. Also, the use of BWS during overground walking could be incorporated into the locomotor treatment program of less affected stroke patients. An electromechanical gait trainer relieving the strenuous effort of the therapists and controlling the trunk in a phase-dependent manner is a new technical alternative for severe stroke patients.

Body Weight↗

PubMed1986

Synthesis of rat brain DNA during acquisition of an appetitive task.

We have examined the incorporation of [3H-methyl]thymidine into DNA extracted from several brain regions of rats learning a reverse handedness task, of control rats allowed to use their preferred paw, and of control rats left in their home cages. In learning animals, decrements in percent incorporation were observed in the visual cortex, remaining brain, hippocampus and entorhinal cortex. In the latter two regions less marked decreases were present in the active control group. No variation occurred in the sensory-motor cortex. In learning rats the specific radioactivity of neuronal DNA was markedly decreased in the hippocampus and remaining brain. In the former region, a less marked decrease was present in active control rats. In subcellular fractionation studies it was observed that decreases in DNA specific radioactivity prevailed in the mitochondrial fraction isolated from the hippocampus and visual cortex of learning rats. Brain radioactive DNA was widely distributed among fractions differing in their degree of repetitiveness. Its pattern of distribution did not coincide with that of bulk DNA and differed significantly among behavioural groups. The results suggest a non random origin of newly-synthesized brain DNA and its involvement in learning.

Animals↗

PubMed1998

Neural control of rotational kinematics within realistic vestibuloocular coordinate systems.

Previous theoretical investigations of the three-dimensional (3-D) angular vestibuloocular reflex (VOR) have separately modeled realistic coordinate transformations in the direct velocity path or the nontrivial problems of converting angular velocity into a 3-D orientation command. We investigated the physiological and behavioral implications of combining both approaches. An ideal VOR was simulated using both a plant model with head-fixed eye muscle actions (standard plant) and one with muscular position dependencies that facilitate Listing's law (linear plant). In contrast to saccade generation, stabilization of the eye in space required a 3-D multiplicative (tensor) interaction between the various components of velocity and position in both models: in the indirect path of the standard plant version, but also in the direct path of the linear plant version. We then incorporated realistic nonorthogonal coordinate transformations (with the use of matrices) into both models. Each now malfunctioned, predicting ocular drift/retinal destabilization during and/or after the head movement, depending on the plant version. The problem was traced to the standard multiplication tensor, which was only defined for right-handed, orthonormal coordinates. We derived two solutions to this problem: 1) separating the brain stem coordinate transformation into two (sensory and motor) transformations that reordered and "undid" the nonorthogonalities of canals and muscle transformations, thus ensuring orthogonal brain stem coordinates, or 2) computing the correct tensor components for velocity-orientation multiplication in arbitrary coordinates. Both solutions provided an ideal VOR. A similar problem occurred with partial canal or muscle damage. Altering a single brain stem transformation was insufficient because the resulting coordinate changes rendered the multiplication tensor inappropriate. This was solved by either recomputing the multiplication tensor, or recomputing the appropriate internal sensory or motor matrix to normalize and reorthogonalize the brain stem. In either case, the multiplication tensor had to be correctly matched to its coordinate system. This illustrates that neural coordinate transformations affect not only serial/parallel projections in the brain, but also lateral projections associated with computations within networks/nuclei. Consequently, a simple progression from sensory to motor coordinates may not be optimal. We hypothesize that the VOR uses a dual coordinate transformation (i.e., both sensory and motor) to optimize intermediate brain stem coordinates, and then sets the appropriate internal tensor for these coordinates. We further hypothesize that each of these processes should optimally be capable of specific, experimentally identifiable adjustments for motor learning and recovery from damage.

Brain Stem↗

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↗