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PubMed2000

Brain oscillations control hand orthosis in a tetraplegic.

The aim of the present study was to investigate whether self-induced brain potential changes could be useful as control signals for patients with severe motor impairment, i.e. due to high-level spinal cord injury. The pilot project was performed in a tetraplegic patient (T.S.), whose residual muscle activity of the upper limbs is restricted to the left biceps. To restore the hand grasp function, an electrical driven hand orthosis fitting his left hand was developed. The operation of this device is directly based on the bioelectrical signals of the brain. After some months of training, T. S. has learned to operate the hand orthosis by mental imagination of specific motor commands.

Adult↗

PubMed1997

Analogical transfer is effective in a serial reaction time task in Parkinson's disease: evidence for a dissociable form of sequence learning.

Several studies of procedural learning in Parkinson's disease (PD) have demonstrated that these patients are impaired with respect to age-matched control subjects. In order to examine more closely the specific impairment, we considered three dimensions along which a procedural learning task could vary. These are: (1) implicit vs explicit learning, (2) instance vs rule learning, and (3) learning with internal vs external error correction. We consider two hypotheses that could explain the impairments observed in PD for different types of explicit motor learning: (H1) an impairment related to the acquisition of rules vs specific instances, and (H2) an impairment in learning when no explicit error feedback is provided. In order to examine the condition of rule learning with external error feedback, we developed a modified version of the serial reaction time (SRT) protocol that tests analogical transfer in sequence learning (ATSL). Reaction times are measured for responses to visual stimuli that appear in several different repeating sequences. While these isomorphic sequences are different, they share a common rule. Verbatim learning of a sequence would result in negative transfer from one sequence to a different one, while rule learning would result in positive transfer. Parkinson's patients and age-matched controls demonstrate significant acquisition and positive transfer of the rule between sequences. Our results demonstrate that PD patients are capable of learning and transferring rule or schema-based representations in an explicit learning format, and that this form of learning may be functionally distinct from learning mechanisms that rely on representations of the verbatim or statistical structure of sequences.

Adult↗

PubMed1990

Brain mechanisms underlying motor skill learning in the rat.

Young rats subjected to bilateral brain lesions were subsequently tested for acquisition of eight puzzle-box problems. Lesions to 12 of the 37 brain sites investigated (anterior pretectal area, subthalamus, posterolateral hypothalamus, frontocingulate cortex, anterior thalamus, mediodorsal thalamus, ventromedial thalamus, parafascicular nucleus, mamillary bodies, cerebellum, olfactory bulb, and ventromedial hypothalamus) retarded puzzle-box learning. This study, combined with earlier investigation of 11 additional brain sites, show that 21 of the 48 total brain structures are involved in motor skill learning. These findings suggest that motor skill learning requires the integrity of a nonspecific mechanism and several specific mechanisms, such as vestibular-proprioceptive-kinesthetic discrimination mechanism and probably also response flexibility, visuospatial attentional, visual discrimination and place learning mechanisms.

Animals↗

PubMed1993

Methodological and theoretical issues in neural network models of frontal cognitive functions.

Neural network models have made significant strides in recent years toward modeling of neuropsychological data. In particular, three different research groups, including that of the present authors, have simulated in model networks some of the behavioral effects of frontal lobe damage. In this article we review these models and discuss their significance in terms of hierarchical organization in the nervous system. These models, to varying degrees, incorporate several widely used neural network principles that have also been used to model a wide range of data in other areas such as categorization, conditioning, and motor control. These principles include associative learning, competition, opponent processing, neuromodulation, and interlevel resonant feedback. Specifically, we show how combinations of these principles serve to model the attentional requirements of cognitive tasks and motor plans.

Animals↗

PubMed1998

The acquisition of skilled motor performance: fast and slow experience-driven changes in primary motor cortex.

Behavioral and neurophysiological studies suggest that skill learning can be mediated by discrete, experience-driven changes within specific neural representations subserving the performance of the trained task. We have shown that a few minutes of daily practice on a sequential finger opposition task induced large, incremental performance gains over a few weeks of training. These gains did not generalize to the contralateral hand nor to a matched sequence of identical component movements, suggesting that a lateralized representation of the learned sequence of movements evolved through practice. This interpretation was supported by functional MRI data showing that a more extensive representation of the trained sequence emerged in primary motor cortex after 3 weeks of training. The imaging data, however, also indicated important changes occurring in primary motor cortex during the initial scanning sessions, which we proposed may reflect the setting up of a task-specific motor processing routine. Here we provide behavioral and functional MRI data on experience-dependent changes induced by a limited amount of repetitions within the first imaging session. We show that this limited training experience can be sufficient to trigger performance gains that require time to become evident. We propose that skilled motor performance is acquired in several stages: "fast" learning, an initial, within-session improvement phase, followed by a period of consolidation of several hours duration, and then "slow" learning, consisting of delayed, incremental gains in performance emerging after continued practice. This time course may reflect basic mechanisms of neuronal plasticity in the adult brain that subserve the acquisition and retention of many different skills.

Adult↗

PubMed1998

Transition of brain activation from frontal to parietal areas in visuomotor sequence learning.

We studied the neural correlates of visuomotor sequence learning using functional magnetic resonance imaging (fMRI). In the test condition, subjects learned, by trial and error, the correct order of pressing two buttons consecutively for 10 pairs of buttons (2 x 10 task); in the control condition, they pressed buttons in any order. Comparison between the test condition and the control condition revealed four brain areas specifically related to learning: the dorsolateral prefrontal cortex (DLPFC), the presupplementary motor area (pre-SMA), the precuneus, and the intraparietal sulcus (IPS). We found that the time course of activation during learning was different between these areas. To normalize the individual differences in the speed of learning, we classified the performance of each subject into three learning stages: early, intermediate, and advanced stages. Both the relative increase of signal intensity and the number of activated pixels within the four areas showed significant changes across the learning stages, with different time courses. The two frontal areas, DLPFC and pre-SMA, were activated in the earlier stages of learning, whereas the two parietal areas, precuneus and IPS, were activated in the later stages. Specifically, DLPFC, pre-SMA, precuneus, and IPS were most highly activated in the early stage, in both the early and intermediate stages, in the intermediate stage, and in both the intermediate and advanced stages, respectively. The results suggest that the acquisition of visuomotor sequences requires frontal activation, whereas the retrieval of visuomotor sequences requires parietal activation, which might reflect the transition from the declarative stage to the procedural stage.

Adult↗

PubMed1993

Thermoimaging of the brain.

A new method of neuroimaging is proposed that is based on the recording of weak changes in infra-red radiation from the brain. Thermoencephaloscopy (TES) uses a combination of thermovision and digital image processing techniques and allows one to make a dynamic investigation of the thermal fields of the cerebral cortex through an unopened skull. Today the method is characterized by: (i) differential thermosensitivity of up to 0.002 degrees C; (ii) instrumental temporal resolution 40 ms (25 thermomaps/s); (iii) time of the temperature measurement in the part of an object that correspondes to one pixel on digital thermomap is equal to 2.4 microseconds; (iv) instrumental spatial resolution of up to 70 microns/pixel; and (v) the thermomap size is 10880 pixels (128 x 85). TES allows detection of an appearance and study of topography and dynamics of the small (from 140 to 300 microns) and precisely localized zones of activation or deactivation of the cerebral cortex that are modally and regionally specific with respect to stimuli modality and parameters and to the state of an animal. Up to now such studies were performed with white rats, rabbits, cats, monkeys and humans under different kinds of sensory stimulation, motor tasks, conditioning (associative learning). Fast thermowaves spreading over the brain cortex along specific trajectories were revealed under sensory stimulation. The mechanisms of the recorded phenomena are discussed: (i) joule heating produced by ion currents through membranes of activated neurones; (ii) metabolic thermoproduction; (iii) thermal convection by the local cerebral blood flow; and (iv) thermodipole formation in the cortical foci with changed lCBF.

Animals↗

PubMedDate not supplied

Cerebellar guidance of premotor network development and sensorimotor learning.

Single unit and imaging studies have shown that the cerebellum is especially active during the acquisition phase of certain motor and cognitive tasks. These data are consistent with the hypothesis that particular sensorimotor procedures are acquired and stored in the cerebellar cortex and that this knowledge can then be exported to the cerebral cortex and premotor networks for more efficient execution. In this article we present a model to illustrate how the cerebellar cortex might guide the development of cortical-cerebellar network connections and how a similar mechanism operating in the adult could mediate the exportation of sensorimotor knowledge from the cerebellum to the motor cortex. The model consists of a three-layered recurrent network representing the cerebello-thalamocortical-ponto-cerebellar limb premotor network. The cerebellar cortex is not explicitly modeled. Our simulations show that Hebbian learning combined with weight normalization allows the emergence of reciprocal and modular structure in the limb premotor network. Reciprocal connections allow activity to reverberate around specific loops. Modularity organizes the connections into specific channels. Furthermore, we show that cerebellar learning can be exported to motor cortex through these modular and reciprocal premotor circuits. In particular, we simulate developmental alignment of visuomotor relations and their realignment as a consequence of prism exposure. The exportation of sensorimotor knowledge from the cerebellum to the motor cortex may allow faster and more efficient execution of learned motor responses.

Adult↗

PubMed2002

Cerebellar structure and function: making sense of parallel fibers.

Many parts of the brain have to cooperate in a finely tuned way in order to generate coordinated motor output. Parameters of these cooperations are adjusted during early childhood development and years of motor learning later in life. The cerebellum plays a special role in the concert of these brain structures. With the unusual geometrical arrangement of its neuronal elements, especially of parallel fibers and Purkinje cells the cerebellum is a selective and sensitive detector of a specific class of spatio-temporal activity patterns in the mossy fiber system: sequences of excitatory input which 'move' along the direction of parallel fibers at about 0.5 m/s, i.e. the speed of spike conductance in parallel fibers. Precise spatio-temporal neuronal activity patterns have been shown to occur in two major sources of afference to the cerebellum, the neocortex and the sensory feedback system. Based on our own experimental work and the above-mentioned findings we suggest that the cerebellum detects specific spatio-temporal activity patterns which trigger learned cerebellar output related to motor control and which contributes to the control of precise timing of muscle contraction.

Adult↗

PubMed2004

Some anthropologic factors of performance in rhythmic gymnastics novices.

The aim of the study was to determine motor and morphological factors, and to assess their impact on specific motor skill performance in rhythmic gymnastics (RG). Experimental training process aimed at learning and improving basic movement structures of rhythmic gymnastics was performed for nine months in a sample of 50 female rhythmic gymnastics novices (mean age 7.1 +/- 0.3 years). Seven dimensions in total were isolated by factorial analysis of 13 motor, 11 morphological, and 20 specific rhythmic gymnastics tests. The factors of flexibility (Beta = 0.26; p < 0.05), explosive strength (Beta = 0.25; p < 0.05) and adipose voluminosity (Beta = -0.42; p < 0.001) explains 41% of the success in performing RG basic body elements--jumps, rotations, balance and flexibility (R = 0.64), while the frequency of movement (Beta = 0.44; p < 0.001) and non-adipose voluminosity (Beta = 0.26; p < 0.05) explains 26% of RG-specific manipulations with the apparatus--club, ribbon and ball wrist manipulation (R = 0.52; p < 0.01). According to study results, the RG-training process intended for rhythmic gymnastics novices should be programmed, with preset objectives for the development of flexibility and explosive strength, speed and peripheral joint strength and adipose tissue reduction.

Adipose Tissue↗

PubMed2003

Chunking during human visuomotor sequence learning.

Motor sequence learning is a process whereby a series of elementary movements is re-coded into an efficient representation for the entire sequence. Here we show that human subjects learn a visuomotor sequence by spontaneously chunking the elementary movements, while each chunk acts as a single memory unit. The subjects learned to press a sequence of 10 sets of two buttons through trial and error. By examining the temporal patterns with which subjects performed a visuomotor sequence, we found that the subjects performed the 10 sets as several clusters of sets, which were separated by long time gaps. While the overall performance time decreased by repeating the same sequence, the clusters became clearer and more consistent. The cluster pattern was uncorrelated with the distance of hand movements and was different across subjects who learned the same sequence. We then split a learned sequence into three segments, while preserving or destroying the clusters in the learned sequence, and shuffled the segments. The performance on the shuffled sequence was more accurate and quicker when the clusters in the original sequence were preserved than when they were destroyed. The results suggest that each cluster is processed as a single memory unit, a chunk, and is necessary for efficient sequence processing. A learned visuomotor sequence is hierarchically represented as chunks that contain several elementary movements. We also found that the temporal patterns of sequence performance transferred from the nondominant to dominant hand, but not vice versa. This may suggest a role of the dominant hemisphere in storage of learned chunks. Together with our previous unit-recording and imaging studies that used the same learning paradigm, we predict specific roles of the dominant parietal area, basal ganglia, and presupplementary motor area in the chunking.

Cluster Analysis↗

PubMed1989

Perceptual-motor and attentional correlates of developmental dyscalculia.

From the patient population of a learning disorders clinic, a group of 72 "relative math underachievers" was selected for achievement test performance below grade level on mathematics but at or above grade level on reading, with a difference of at least 1.5 standard deviation between the two. A comparison group of 30 "relative reading underachievers" met the converse criteria. Neurological examination showed mixed laterality preference (right hand and foot but left eye) to be more prevalent among the math underachievers. The two groups were closely comparable on Wechsler intelligence quotient scores, although the "freedom from distractibility quotient" tended to be lower for the match group. The latter group also showed a lower mean achievement quotient on the Bender Visuomotor Gestalt Test. On a standard questionnaire derived from DSM-III criteria for attention deficit disorder, the math group showed higher scores for inattention, but not for hyperactivity, impulsivity, or poor peer relations. Both perceptual-motor and attentional deficits appear to characterize children who are specifically learning disabled for math.

Adolescent↗

PubMed2004

Generalization in vision and motor control.

Learning is more than memory. It is not simply the building of a look-up table of labelled images, or a phone-directory-like list of motor acts and the corresponding sequences of muscle activation. Central to learning and intelligence is the ability to predict, that is, to generalize to new situations, beyond the memory of specific examples. The key to generalization, in turn, is the architecture of the system, more than the rules of synaptic plasticity. We propose a specific architecture for generalization for both the motor and the visual systems, and argue for a canonical microcircuit underlying visual and motor learning.

Animals↗

PubMed2006

Motor learning: its relevance to stroke recovery and neurorehabilitation.

PURPOSE OF REVIEW: Much of neurorehabilitation rests on the assumption that patients can improve with practice. This review will focus on arm movements and address the following questions: (i) What is motor learning? (ii) Do patients with hemiparesis have a learning deficit? (iii) Is recovery after injury a form of motor learning? (iv) Are approaches based on motor learning principles useful for rehabilitation? RECENT FINDINGS: Motor learning can be broken into kinematic and dynamic components. Studies in healthy subjects suggest that retention of motor learning is best accomplished with variable training schedules. Animal models and functional imaging in humans show that the mature brain can undergo plastic changes during both learning and recovery. Quantitative motor control approaches allow differentiation between compensation and true recovery, although both improve with practice. Several promising new rehabilitation approaches are based on theories of motor learning. These include impairment oriented-training (IOT), constraint-induced movement therapy (CIMT), electromyogram (EMG)-triggered neuromuscular stimulation, robotic interactive therapy and virtual reality (VR). SUMMARY: Motor learning mechanisms are operative during spontaneous stroke recovery and interact with rehabilitative training. For optimal results, rehabilitation techniques should be geared towards patients' specific motor deficits and possibly combined, for example, CIMT with VR. Two critical questions that should always be asked of a rehabilitation technique are whether gains persist for a significant period after training and whether they generalize to untrained tasks.

Electric Stimulation Therapy↗

PubMed1993

Motor learning deficits in aged rats are correlated with loss of cerebellar noradrenergic function.

We have demonstrated that aged rats show impairments in learning patterned motor movements. Similar behavioral impairment is observed in rats with noradrenergic lesions. Norepinephrine is known to act as a neuromodulator in the cerebellar cortex because it can augment the action of GABA and other neurotransmitters. This effect of NE to augment the signal to noise ratio of GABAergic inputs to cerebellar Purkinje neurons is a possible substrate for NE's effect on motor learning. Aged rats demonstrate deficits in the modulatory actions of NE to augment GABAergic inhibitions when both substances are locally applied onto cerebellar Purkinje neurons. In this report, we examined how motor learning and cerebellar noradrenergic function varied in individual young and 20-month-old Fischer 344 rats. There was a significant correlation between the loss of the neuromodulatory actions of norepinephrine (NE) in the cerebellar cortex and the rate of learning a novel motor task in individual rats. This report thus demonstrates for the first time a correlation between age-related impairments in motor plasticity and specific neurophysiological deficits in cerebellar Purkinje neurons in individual animals.

Aging↗

PubMed2005

Contributions of the mitogen-activated protein kinase and protein kinase C cascades in spatial learning and memory mediated by the nucleus accumbens.

Several studies have reported a role for the nucleus accumbens (NAcc) in learning and memory. Specifically, NAcc seems to function as a neural bridge for the translation of corticolimbic information to the motor system mediating locomotor learning, but the signaling mechanisms involved in this striatal learning await further investigation. The present experiments investigated the role of the mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) cascades within the NAcc of Long-Evans rats in a food-search spatial learning task (FSSLT). First, we used immunoblotting to examine changes in MAPK p42/p44 phosphorylation within the NAcc in the acquisition phase of the FSSLT. Second, we examined the effect on the acquisition and retention phases in the FSSLT of pretraining intra-accumbal microinjections of the MAPK [U0126; 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophynyltio)butadiene, 1 microg/side] or PKC [GF109203X; bisindolylmaleimide or 1-(3-dimethylaminopropyl)-indol-3-yl]-3-(indol-3-yl) maleimide, 0.5 ng/side] inhibitors (four training sessions; one session/day). Third, the potential coupling of PKC and MAPK signaling pathways in the NAcc in spatial learning was studied using microinjections of GF109203X, radioactive activity assays, and immunoblotting. Results showed that 1) MAPK p42/p44 phosphorylation is augmented within the NAcc after spatial learning, 2) MAPK and PKC inhibition caused differential deficits in the acquisition and formation of spatial memories, and 3) inhibition of PKC activity by GF109203X caused a reduction in MAPKs phosphorylation in the NAcc in an early stage of the acquisition phase. Overall, these findings suggest that NAcc-PKC and -MAPK play important roles in spatial learning and that MAPKs phosphorylation seems to be mediated through the activation of the PKC signaling pathway.

Animals↗

PubMed2000

Neural bases of learning and memory: functional neuroimaging evidence.

Positron emission tomography and functional magnetic resonance imaging studies have identified brain regions associated with different forms of memory. Working memory has been associated primarily with the bilateral prefrontal and parietal regions; semantic memory with the left prefrontal and temporal regions; episodic memory encoding with the left prefrontal and medial temporal regions; episodic memory retrieval with the right prefrontal, posterior midline and medial temporal regions; and skill learning with the motor, parietal, and subcortical regions. Recent studies have provided higher specificity, by dissociating the neural correlates of different subcomponents of complex memory tasks, and the cognitive roles of different subregions of larger brain areas.

Brain↗

PubMed1995

Modulation of muscle responses evoked by transcranial magnetic stimulation during the acquisition of new fine motor skills.

1. We used transcranial magnetic stimulation (TMS) to study the role of plastic changes of the human motor system in the acquisition of new fine motor skills. We mapped the cortical motor areas targeting the contralateral long finger flexor and extensor muscles in subjects learning a one-handed, five-finger exercise on the piano. In a second experiment, we studied the different effects of mental and physical practice of the same five-finger exercise on the modulation of the cortical motor areas targeting muscles involved in the task. 2. Over the course of 5 days, as subjects learned the one-handed, five-finger exercise through daily 2-h manual practice sessions, the cortical motor areas targeting the long finger flexor and extensor muscles enlarged, and their activation threshold decreased. Such changes were limited to the cortical representation of the hand used in the exercise. No changes of cortical motor outputs occurred in control subjects who underwent daily TMS mapping but did not practice on the piano at all (control group 1). 3. We studied the effect of increased hand use without specific skill learning in subjects who played the piano at will for 2 h each day using only the right hand but who were not taught the five-finger exercise (control group 2) and who did not practice any specific task. In these control subjects, the changes in cortical motor outputs were similar but significantly less prominent than in those occurring in the test subjects, who learned the new skill.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗