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PubMed1999

Perceptual-motor sequence learning of general regularities and specific sequences.

Participants viewed digit strings and typed them on a computer keyboard. When they used the same key configuration across training and test, they typed test strings that adhered to the same sequence rule as training strings faster than test strings that adhered to the opposite rule (general-regularity [GR] learning), and they typed test strings that were processed repeatedly during training faster than test strings that were not (specific-sequence [SS] learning). However, when they used different key configurations at training and at test, GR learning, but not SS learning, was observed. Conversely, when they did not type but spoke the strings aloud during training, SS learning, but not GR learning, was observed. Results suggest that in addition to declarative memory for specific sequences, relatively independent subsystems underlie procedural learning of perceptual-motor sequence components (producing GR effects) and sequence wholes (producing SS effects).

Female↗
PubMedDate not supplied

The olive and central control of blood pressure.

This evidence, then, would suggest that the olive becomes active when, with a change in the motor task, the motor performance is required to adjust to the new circumstance. From Smith's experiments on blood pressure, it is extrapolated that the olive becomes active when there is a change in the physiological state, and the autonomic performance is required to adjust to the new circumstance. The important point is that the olive does have an experimental effect on blood pressure, and that it is a specific, though indirect, effect acting through the carotid sinus reflex. This effect appears similar to the effect on motor control which is specific for motor learning, and appears to act indirectly through the cerebellum. The hypothesis is being put forward because of the importance of blood pressure abnormalities, and the possible therpeutic benefits to be derived from an understanding of the central control of blood pressure. It is hoped that in pursuing this elusive control system one shall not overlook the olive.

Animals↗
PubMed2004

Role of the cerebellum in eyeblink conditioning.

The mammalian cerebellum is thought to participate in motor control and motor learning. The specific cerebellar contribution to these processes is not clear, however. Advances in understanding cerebellar function have been relatively slow, because, at least in most cases, the cerebellum appears to play only an ancillary role in the behaviors studied to date. A remarkable exception is classical conditioning of eyeblink responses in the rabbit. In this model, an intact cerebellum is critical for both the acquisition and expression of conditioned responses. Recent experiments suggest that the cerebellar role in classical conditioning might be similar in all mammals, including the human. Moreover, anticipatory defensive reflexes in other effector systems show a similar dependence on the intermediate cerebellum. Further developments in our understanding of cerebellar function will depend on examination of a wider array of cerebellar-involved neural networks. There is also need for the development of new experimental approaches to associative learning in both the nonhuman primate and the human.

Animals↗
PubMed2001

Transgenic mice with neuronal overexpression of bcl-2 gene present navigation disabilities in a water task.

In the CNS, Bcl-2 is an antiapoptotic gene involved in the regulation of neuronal death. Transgenic mice overexpressing the human gene Bcl-2 (Hu-bcl-2 mice) showed delayed acquisition in two tasks requiring them to find a hidden platform starting from either a random or a constant starting location. The same mice were not deficient in another task requiring them to find a visible platform suggesting that the delay observed was not due to motor, visual or motivational deficits in the water. The delay observed in Hu-bcl-2 mice was more important in the random starting test in which the allocentric demand for navigation was stronger. The results suggested that allocentric navigation is particularly sensitive to abnormal CNS maturation following the overexpression of the bcl-2 gene. The specific deficits (motor learning, fear-related behavior and allocentric navigation) observed in Hu-bcl-2 mice suggest that the regulation of developmental neuronal death is crucial for multisensorial learning and emotional behavior.

Animals↗
PubMed1987

Motor learning: nonspecific subcortical mechanisms in rats.

Adult rats with bilateral lesions in the globus pallidus, substantia nigra, median raphe, midbrain central gray, or pontine reticular formation were tested for novel motor skill learning (sliding a barrel bolt to the right in order to open a door leading to a reward). Significantly impaired learning was found in animals with lesions to globus pallidus, substantia nigra, median raphe, or pontine reticular formation. These results combined with earlier findings suggest that the foregoing subcortical structures along with the regions of the ventrolateral and parafascicular nuclei of the thalamus constitute a nonspecific mechanism involved not only in motor learning but in discrimination and maze learning as well. This mechanism is contrasted with the more fashionable specific mechanisms which are involved in particular classes of learning; the sensorimotor cortex, for example, would be a component of the specific mechanism underlying motor learning. A subcortical nonspecific learning mechanism may also inhabit the human brain, as suggested by the clinical condition of "subcortical dementia."

Animals↗
PubMed2006

fMRI investigation of cortical and subcortical networks in the learning of abstract and effector-specific representations of motor sequences.

A visuo-motor sequence can be learned as a series of visuo-spatial cues or as a sequence of effector movements. Earlier imaging studies have revealed that a network of brain areas is activated in the course of motor sequence learning. However, these studies do not address the question of the type of representation being established at various stages of visuo-motor sequence learning. In an earlier behavioral study, we demonstrated that acquisition of visuo-spatial sequence representation enables rapid learning in the early stage and progressive establishment of somato-motor representation helps speedier execution by the late stage. We conducted functional magnetic resonance imaging (fMRI) experiments wherein subjects learned and practiced the same sequence alternately in normal and rotated settings. In one rotated setting (visual), subjects learned a new motor sequence in response to an identical sequence of visual cues as in normal. In another rotated setting (motor), the display sequence was altered as compared to normal, but the same sequence of effector movements was used to perform the sequence. Comparison of different rotated settings revealed analogous transitions both in the cortical and subcortical sites during visuo-motor sequence learning-a transition of activity from parietal to parietal-premotor and then to premotor cortex and a concomitant shift was observed from anterior putamen to a combined activity in both anterior and posterior putamen and finally to posterior putamen. These results suggest a putative role for engagement of different cortical and subcortical networks at various stages of learning in supporting distinct sequence representations.

Adult↗
PubMed1990

Specificity and variability of practice.

The specificity of learning principle proposes that motor skills are specific and only superficially resemble other similar skills or variations of the same skill. On the other hand, the variability of practice hypothesis derived from schema theory proposes that experiences with task variations are vital to the development of the memories (schemata) responsible for response production and learning. This paper contrasts these two positions in two experiments aimed at determining the influence of providing variable and/or specific acquisition experiences on the retention of a force production task. The results clearly indicated that acquisition practice with variations of the criterion task leads to better retention than practice on the criterion task alone. This finding is contrary to a strict interpretation of the specificity of learning principle and suggests that paradigms investigating schema notions should be expanded to include potential impacts of variability of practice on tasks experienced during acquisition.

Biofeedback, Psychology↗
PubMed2001

The cerebellum-specific Munc13 isoform Munc13-3 regulates cerebellar synaptic transmission and motor learning in mice.

Munc13 proteins form a family of three, primarily brain-specific phorbol ester receptors (Munc13-1/2/3) in mammals. Munc13-1 is a component of presynaptic active zones in which it acts as an essential synaptic vesicle priming protein. In contrast to Munc13-1, which is present in most neurons throughout the rat and mouse CNS, Munc13-3 is almost exclusively expressed in the cerebellum. Munc13-3 mRNA is present in granule and Purkinje cells but absent from glia cells. Munc13-3 protein is localized to the synaptic neuropil of the cerebellar molecular layer but is not found in Purkinje cell dendrites, suggesting that Munc13-3, like Munc13-1, is a presynaptic protein at parallel fiber-Purkinje cell synapses. To examine the role of Munc13-3 in cerebellar physiology, we generated Munc13-3-deficient mutant mice. Munc13-3 deletion mutants exhibit increased paired-pulse facilitation at parallel fiber-Purkinje cell synapses. In addition, mutant mice display normal spontaneous motor activity but have an impaired ability to learn complex motor tasks. Our data demonstrate that Munc13-3 regulates synaptic transmission at parallel fiber-Purkinje cell synapses. We propose that Munc13-3 acts at a similar step of the synaptic vesicle cycle as does Munc13-1, albeit with less efficiency. In view of the present data and the well established vesicle priming function of Munc13-1, it is likely that Munc13-3-loss leads to a reduction in release probability at parallel fiber-Purkinje cell synapses by interfering with vesicle priming. This, in turn, would lead to increases in paired-pulse facilitation and could contribute to the observed deficit in motor learning.

Animals↗
PubMed2000

Patterns of regional brain activation associated with different forms of motor learning.

To examine the variations in regional cerebral blood flow during execution and learning of reaching movements, we employed a family of kinematically and dynamically controlled motor tasks in which cognitive, mnemonic and executive features of performance were differentiated and characterized quantitatively. During 15O-labeled water positron emission tomography (PET) scans, twelve right-handed subjects moved their dominant hand on a digitizing tablet from a central location to equidistant targets displayed with a cursor on a computer screen in synchrony with a tone. In the preceding week, all subjects practiced three motor tasks: 1) movements to a predictable sequence of targets; 2) learning of new visuomotor transformations in which screen cursor motion was rotated by 30 degrees -60 degrees; 3) learning new target sequences by trial and error, by using previously acquired routines in a task placing heavy load on spatial working memory. The control condition was observing screen and audio displays. Subtraction images were analyzed with Statistical Parametric Mapping to identify significant brain activation foci. Execution of predictable sequences was characterized by a modest decrease in movement time and spatial error. The underlying pattern of activation involved primary motor and sensory areas, cerebellum, basal ganglia. Adaptation to a rotated reference frame, a form of procedural learning, was associated with decrease in the imposed directional bias. This task was associated with activation in the right posterior parietal cortex. New sequences were learned explicitly. Significant activation was found in dorsolateral prefrontal and anterior cingulate cortices. In this study, we have introduced a series of flexible motor tasks with similar kinematic characteristics and different spatial attributes. These tasks can be used to assess specific aspects of motor learning with imaging in health and disease.

Adult↗
PubMed2000

Implicit motor sequence learning is represented in response locations.

Previous work (Willingham, 1999) has indicated that implicit motor sequence learning is not primarily perceptual; that is, what is learned is not a sequence of stimuli. Still other work has indicated that implicit motor sequence learning is not specific to particular muscle groups or effectors. In the present work, we tested whether implicit motor sequence learning would be represented as a sequence of response locations. In Experiment 1, learning showed very poor transfer when the response locations were changed, even though the stimulus positions were unchanged. In Experiment 2, participants switched their hand positions at transfer, so that one group of participants pushed the same sequence of keys but used a different sequence of finger movements to do so, whereas another group pushed a different sequence of keys but used the same sequence of finger movements used at training. Knowledge of the sequence was shown at transfer only if the sequence of response locations was maintained, not the sequence of finger movements.

Adult↗
PubMed1993

On the cerebellum and motor learning.

A critical review of the role of the cerebellum in motor learning is presented. Specifically, the hypothesis that the climbing fibers that issue from the inferior olive serve to modify the responsiveness of cerebellar Purkinje cells is evaluated. It is concluded that there is no convincing evidence, at this time, to support the view that a long-term modification of Purkinje cell activity is either the basis of motor learning or an authentic mechanism of cerebellar function. An alternative view, based on the biophysical, anatomical and ensemble properties of olivary neurons, suggests an important role for the olivocerebellar system in the coordination of movements. Future work in this interesting area of neuroscience will distinguish these two hypotheses.

Animals↗
PubMed2004

Learning-induced improvement in encoding and decoding of specific movement directions by neurons in the primary motor cortex.

Many recent studies describe learning-related changes in sensory and motor areas, but few have directly probed for improvement in neuronal coding after learning. We used information theory to analyze single-cell activity from the primary motor cortex of monkeys, before and after learning a local rotational visuomotor task. We show that after learning, neurons in the primary motor cortex conveyed more information about the direction of movement and did so with relation to their directional sensitivity. Similar to recent findings in sensory systems, this specific improvement in encoding is correlated with an increase in the slope of the neurons' tuning curve. We further demonstrate that the improved information after learning enables a more accurate reconstruction of movement direction from neuronal populations. Our results suggest that similar mechanisms govern learning in sensory and motor areas and provide further evidence for a tight relationship between the locality of learning and the properties of neurons; namely, cells only show plasticity if their preferred direction is near the training one. The results also suggest that simple learning tasks can enhance the performance of brain-machine interfaces.

Animals↗
PubMed2006

Importance of K+-dependent Na+/Ca2+-exchanger 2, NCKX2, in motor learning and memory.

Plasma membrane Na+/Ca2+-exchangers play a predominant role in Ca2+ extrusion in brain. Neurons express several different Na+/Ca2+-exchangers belonging to both the K+-independent NCX family and the K+-dependent NCKX family. The unique contributions of each of these proteins to neuronal Ca2+ homeostasis and/or physiology remain largely unexplored. To address this question, we generated mice in which the gene encoding the abundant neuronal K+ -dependent Na+/Ca2+-exchanger protein, NCKX2, was knocked out. Analysis of these animals revealed a significant reduction in Ca2+ flux in cortical neurons, a profound loss of long term potentiation and an increase in long term depression at hippocampal Schaffer/CA1 synapses, and clear deficits in specific tests of motor learning and spatial working memory. Surprisingly, there was no obvious loss of photoreceptor function in cones, where expression of the NCKX2 protein had been reported previously. These data emphasize the critical and non-redundant role of NCKX2 in the local control of neuronal [Ca2+] that is essential for the development of synaptic plasticity associated with learning and memory.

Animals↗
PubMed1997

Increased Sensitivity to Changes in Visual Feedback With Practice.

In recent work investigating motor learning, the focus has been on the effect of modifying feedback at different levels of learning. Results suggest that learning is specific to the practiced conditions and that this specificity increases with practice. In a replication and extension of this previous work, 3 groups (N = 30 subjects) practiced a sequential positioning movement: Controls performed 300 trials with visually presented on-line kinematic feedback, whereas the other 2 groups, low practice (LP) or high practice (HP), performed, respectively, 50 or 300 trials without feedback. Pretest and posttest sessions of 10 trials each were performed with the on-line feedback. All groups improved with practice. It was apparent that the HP group exhibited more of a performance decrement in the posttest than the LP group did, suggesting that motor learning is the process of forming an increasingly specific sensorimotor representation. These results have implications for motor learning paradigms, models of motor learning, and training.

humans↗
PubMed2005

Specificity of sensorimotor learning and the neural code: neuronal representations in the primary motor cortex.

Human studies show that the learning of a new sensorimotor mapping that requires adaptation to directional errors is local and generalizes poorly to untrained directions. We trained monkeys to learn new visuomotor rotations for only one target in space and recorded neuronal activity in the primary motor cortex before, during and after learning. Similar to humans, the monkeys showed poor transfer of learning to other directions, as observed by behavioral aftereffects for untrained directions. To test for internal representations underlying these changes, we compared two features of neuronal activity before and after learning: changes in firing rates and changes in information content. Specific elevations of firing rate were only observed in a subpopulation of cells in the motor cortex with directional properties corresponding to the locally learned rotation; namely cells only showed plasticity if their preferred direction was near the training one. We applied measures from information theory to probe for learning-related changes in the neuronal code. Single cells conveyed more information about the direction of movement and this specific improvement in encoding was correlated with an increase in the slope of the neurons' tuning curve. Further, the improved information after learning enabled a more accurate reconstruction of movement direction from neuronal populations. Our findings suggest a neural mechanism for the confined generalization of a newly acquired internal model by showing a tight relationship between the locality of learning and the properties of neurons. They also provide direct evidence for improvement in the neural code as a result of learning.

Action Potentials↗
PubMed1987

Metabolic mapping of sensorimotor integration in the human brain.

Studies of regional cerebral flow and regional cerebral oxidative metabolism have revealed that humans have three major cortical motor areas: the premotor, supplementary motor and primary motor areas. The premotor area participates in organizing non-routine voluntary movements, especially those carried out contingent to or dependent on sensory information. The supplementary motor area participates in the planning of all motor subroutines. The primary motor area is the executive locus for voluntary movements. Subcortically the caudate nucleus, putamen, globus pallidus, parasagittal cerebellum and ventral thalamus are the main structures which increase their metabolism during voluntary movements of the upper limbs. All these cortical and subcortical structures except the primary motor area are bilaterally activated even during strictly unilateral movements of the upper limbs. However, recent studies of oxidative metabolism show that the caudate nucleus, putamen and lateral cerebellum also participate in cognitive functions and non-motor learning. Before any specific brain work is executed, voluntary movements included, the brain tunes and prepares cortical fields measuring a few square centimetres in the areas that are supposed to participate in information transmission. The superior prefrontal cortex has a special role in this recruitment of cortical fields. Depending on the information needed to execute the voluntary movements, cortical fields are activated in the anterior parietal lobe and the dysgranular frontal cortex.

Brain↗
PubMed1995

Cerebellar long-term depression might normalize excitation of Purkinje cells: a hypothesis.

Long-term depression (LTD) of parallel-fibre (PF) synapses on Purkinje cells is usually interpreted in the context of a specific theory of motor learning by the cerebellum proposed by Marr, Albus and Ito. Several arguments suggest that this theory might be false. A new hypothesis about the role of cerebellar LTD proposes that, under physiological conditions, LTD is autoinduced by PF inputs. This proposal is based on the capacity of PF inputs to trigger influx of Ca2+ into the dendrite. Long-term depression and other forms of Purkinje-cell synaptic plasticity are part of a local negative feedback loop that prevents overstimulation of Purkinje cells by PF inputs. This theory explains why it is difficult to induce LTD when a normal level of inhibition is present, and why inhibitory inputs are potentiated by the same conditions that can induce LTD of PF synapses.

Animals↗