Neuronal activity in the primate supplementary motor area and the primary motor cortex in relation to spatio-temporal bimanual coordination

Single neuronal activity was recorded from the supplementary motor area (SMA-proper and pre-SMA) and primary motor cortex (M1) in two Macaca fascicularis trained to perform a delayed conditional sequence of coordinated bimanual pull and grasp movements. The behavioural paradigm was designed to distinguish neuronal activity associated with bimanual coordination from that related to a comparable motor sequence but executed unimanually (left or right arm only). The bimanual and unimanual trials were instructed in a random order by a visual cue. Following the cue, there was a waiting period until presentation of a "go-signal", signalling the monkey to perform the instructed movement. A total of 143 task-related neurons were recorded from the SMA (SMA-proper, 62; pre-SMA, 81). Most SMA units (87%) were active in both unimanual contralateral and unimanual ipsilateral trials (bilateral neurons), whereas 9% of units were active only in unimanual contralateral trials and 3% were active only in unimanual ipsilateral trials. Forty-eight per cent of SMA task-related units were classified as bimanual, defined as neurons in which the activity observed in bimanual trials could not be predicted from that associated with unimanual trials when comparing the same events related to the same arm. For direct comparison, 527 neurons were recorded from M1 in the same monkeys performing the same tasks. The comparison showed that M1 contains significantly less bilateral neurons (75%) than the SMA, whereas the reverse was observed for contralateral neurons (22% in M1). The proportion of M1 bimanual cells (53%) was not statistically different from that observed in the SMA. The results suggest that both the SMA and M1 may contribute to the control of sequential bimanual coordinated movements. Interlimb coordination may then take place in a distributed network including at least the SMA and M1, but the contribution of other cortical and subcortical areas such as cingulate motor cortex and basal ganglia remains to be investigated.     

Effects of reversible inactivation of the supplementary motor area (SMA) on unimanual grasp and bimanual pull and grasp performance in monkeys

The supplementary motor area (SMA) was reversibly inactivated by muscimol microinfusion in two monkeys while they were performing two motor tasks: (1) a delayed conditional bimanual drawer pulling and grasping sequence which was initiated on a self-paced basis; (2) a unimanual reach and grasp task (modified Kluver board task). Unilateral or bilateral inactivation of the SMA induced a prominent deficit in trial initiation of bimanual sequential movements, affecting the hand contralateral to the inactivated side or both hands, respectively. The deficit was a long lasting (10-15 min or more) inability of the monkey to place its hand (s) in the ready position on start touch-sensitive pads, a condition required to initiate the drawer task. However, if after such a deficit period, the experimenter put his hand on the start touch-sensitive pad to initiate the trial, then the monkey executed the drawer task without obvious motor deficit. SMA inactivation did not affect unimanual reaching and grasping movements in the board task. In contrast to the SMA, inactivation of other motor areas (primary, premotor dorsal, anterior intraparietal area) did not affect the initiation of movement sequences in the drawer task. These data thus indicate that the SMA plays a crucial and specific role in initiation of self-paced movement sequences. However, SMA inactivation did not prevent the monkeys to perform coordinated movements of the two forelimbs and hands, indicating that SMA is not necessary for bimanual coordination.     

Role for cells in the presupplementary motor area in updating motor plans

Two motor areas are known to exist in the medial frontal lobe of the cerebral cortex of primates, the supplementary motor area (SMA) and the presupplementary motor area (pre-SMA). We report here on an aspect of cellular activity that characterizes the pre-SMA. Monkeys were trained to perform three different movements sequentially in a temporal order. The correct order was planned on the basis of visual information before its execution. A group of pre-SMA cells (n = 64, 25%) were active during a process when monkeys were required to discard a current motor plan and develop a plan appropriate for the next orderly movements. Such activity was not common in the SMA and not found in the primary motor cortex. Our data suggest a role of pre-SMA cells in updating motor plans for subsequent temporally ordered movements.     

Movement sequence-related activity reflecting numerical order of components in supplementary and presupplementary motor areas

The supplementary motor area (SMA) and presupplementary motor areas (pre-SMA) have been implicated in movement sequencing, and neurons in SMA have been shown to encode what might be termed the relational order among sequence components (e.g., movement X followed by movement Y). To determine whether other aspects of movement sequencing might also be encoded by SMA or pre-SMA neurons, we analyzed task-related activity recorded from both areas in conjunction with a sequencing task that dissociated the numerical order of components (e.g., movement X as the 2nd component, irrespective of which movements precede or follow X). Sequences were constructed from eight component movements, each characterized by three spatial variables (origin, direction, and endpoint). Task-related activity recorded from 56 SMA and 63 pre-SMA neurons was categorized according to both the epoch (delay, reaction time, and movement time) and the spatial variable or component movement with which it was associated. All but one instance of task-related activity was selective for one of the spatial variables (SV-selective) rather than for any of the component movements themselves. Of 110 instances of SV-selective activity in SMA, 43 (39%) showed significant effects of numerical order. The corresponding incidence in pre-SMA, 82 (71%) of 116, was substantially higher (P < 0.00001). No effects of numerical order were evident among the hand paths, movement times, or electromyographic activity associated with task performance. We concluded that neurons in SMA and pre-SMA may encode the numerical order of components, at least for sequences that are distinguished mainly by that aspect of component ordering.     

Corticostriatal input zones from the supplementary motor area overlap those from the contra- rather than ipsilateral primary motor cortex

To investigate the degree of convergence of corticostriatal inputs from the primary motor cortex (MI) and the supplementary motor area (SMA), we analyzed the extent to which corticostriatal inputs from forelimb representations of these motor-related areas spatially overlap in the macaque monkey. Of particular interest was that corticostriatal input zones from SMA overlapped those from MI of the contralateral hemisphere more extensively than from MI of the ipsilateral hemisphere.     

Changing directions of forthcoming arm movements: neuronal activity in the presupplementary and supplementary motor area of monkey cerebral cortex

1. To understand roles played by two cortical motor areas, the presupplementary motor area (pre-SMA) and supplementary motor area (SMA), in changing planned movements voluntarily, cellular activity was examined in two monkeys (Macaca fuscata) trained to perform an arm-reaching task in which they were asked to press one of two target buttons (right or left) in three different task modes. 2. In the first mode (visual), monkeys were visually instructed to result and press either a right or left key in response to a forth coming trigger signal. In the second mode (stay), monkeys were required to wait for the trigger signal and press the same target key as pressed in preceding trials. In the third mode (shift), a 50 Hz auditory cue instructed the monkey to shift the target of the future reach from the previous target to the previous nontarget. 3. While the monkeys were performing this task, we recorded 399 task-related cellular activities from the SMA and the pre-SMA. Among them, we found a group of neurons that exhibited activity changes related specifically to shift trials (shift-related cells). The following properties characterized these 112 neurons. First, they exhibited activity changes after the onset of the 50-Hz auditory cue and before the movement execution when the monkeys were required to change the direction of forthcoming movement. Second, they were not active when the monkeys pressed the same key without changing the direction of the movements. Third, they were not active when the monkeys received the 50-Hz auditory cue but failed to change the direction of the movements by mistake. These observations indicate that the activity of shift-related cells is related to the redirection of the forthcoming movements, but not to the auditory instruction itself or to the location of the target key or the direction of the forthcoming movements. 4. Although infrequently, monkeys made errors in the stay trials and changed directions of the reach voluntarily. In that case, a considerably high proportion of shift-related neurons (12 of 19) exhibited significant activity changes long before initiation of the reach movement. These long-lasting activities were not observed during the preparatory period in correct stay trials, but resembled the shift-related activity observed when the target shift was made toward the same direction. Thus these activity changes were considered to be also related to the process of changing the intended movements voluntarily. 5. We found another population of neurons that showed activity modulation when the target shift was induced by the visual instruction in visual trials (visually guided shift-related neurons). These neurons were active when the light-emitting diode (LED) guided the forthcoming reach to the previous nontarget but not to the previous target. Therefore their activity was not a simple visual response to the LED per se. A majority of them also showed shift-related activity in shift trials (19 of 22 in monkey 2). 6. Neurons exhibiting the shift-related activity were distributed differentially among the two areas. In the pre-SMA, 31% of the neurons recorded showed the shift-related activity, whereas in the SMA, only 7% showed such an activity. These results suggest that pre-SMA and SMA play differential roles in updating the motor plans in accordance with current requirements.     

The developmental origins of bimanual coordination: A dynamic perspective.

Patterns of interlimb coordination associated with infant reaching fluctuate frequently over developmental time. This study investigated whether these fluctuations are related to coordination tendencies. Interlimb patterns were studied in reaching and nonreaching movements in 4 infants, which were followed through their 1st year. Each week, reaching and nonreaching endpoint kinematics were recorded in both arms during multiple 14-s trials. It was found that patterns of interlimb coordination in reaching matched coordination tendencies in nonreaching. Reaching fluctuated between uni- and bimanual periods. During the bimanual periods, nonreaching interlimb activity tended to be synchronous. During the unimanual periods, nonreaching activity revealed no predominant form of interlimb coordination. It is argued that changing coordination tendencies may influence the organization of specific goal-oriented behaviors from early in life. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Retinal arterial occlusions in young adults

Stereotactic posteroventral pallidotomy can improve motor performance in Parkinson's disease. Interruption of inhibitory pallidal projections to ventrolateral thalamus, components of a cortical-basal ganglia motor loop allows for this clinical benefit. We hypothesized that pallidotomy would lead to increased movement related activity in motor cortical areas receiving projections from ventrolateral thalamus. This was tested in 6 Parkinson's disease patients who underwent stereotactic posteroventral pallidotomy. Each patient was imaged with positron emission tomography (PET) measures of regional cerebral blood flow (rCBF) during performance of a simple prehension task and at rest. Scans were acquired before and 17 weeks after surgery. After pallidotomy, movement-related changes of rCBF increased significantly in both the supplementary motor area (SMA) and premotor cortex but not in primary motor cortex. The results demonstrate the importance of pallidothalamic circuitry for regulating volitional movements and confirm that disruption of inhibitory input to the ventrolateral thalamus can augment movement-related activity in motor association areas.     

Coding of intention in the posterior parietal cortex

To look at or reach for what we see, spatial information from the visual system must be transformed into a motor plan. The posterior parietal cortex (PPC) is well placed to perform this function, because it lies between visual areas, which encode spatial information, and motor cortical areas. The PPC contains several subdivisions, which are generally conceived as high-order sensory areas. Neurons in area 7a and the lateral intraparietal area fire before and during visually guided saccades. Other neurons in areas 7a and 5 are active before and during visually guided arm movements. These areas are also active during memory tasks in which the animal remembers the location of a target for hundreds of milliseconds before making an eye or arm movement. Such activity could reflect either visual attention or the intention to make movements. This question is difficult to resolve, because even if the animal maintains fixation while directing attention to a peripheral location, the observed neuronal activity could reflect movements that are planned but not executed. To address this, we recorded from the PPC while monkeys planned either reaches or saccades to a single remembered location. We now report that, for most neurons, activity before the movement depended on the type of movement being planned. We conclude that PPC contains signals related to what the animal intends to do.     

Functional anatomy of pointing and grasping in humans

The functional anatomy of reaching and grasping simple objects was determined in nine healthy subjects with positron emission tomography imaging of regional cerebral blood flow (rCBF). In a prehension (grasping) task, subjects reached and grasped illuminated cylindrical objects with their right hand. In a pointing task, subjects reached and pointed over the same targets. In a control condition subjects looked at the targets. Both movement tasks increased activity in a distributed set of cortical and subcortical sites: contralateral motor, premotor, ventral supplementary motor area (SMA), cingulate, superior parietal, and dorsal occipital cortex. Cortical areas including cuneate and dorsal occipital cortex were more extensively activated than ventral occipital or temporal pathways. The left parietal operculum (putative SII) was recruited during grasping but not pointing. Blood flow changes were individually localized with respect to local cortical anatomy using sulcal landmarks. Consistent anatomic landmarks from MRI scans could be identified to locate sensorimotor, ventral SMA, and SII blood flow increases. The time required to complete individual movements and the amount of movement made during imaging correlated positively with the magnitude of rCBF increases during grasping in the contralateral inferior sensorimotor, cingulate, and ipsilateral inferior temporal cortex, and bilateral anterior cerebellum. This functional-anatomic study defines a cortical system for "pragmatic' manipulation of simple neutral objects.     

Variability and correlated noise in the discharge of neurons in motor and parietal areas of the primate cortex

We analyzed the magnitude and interneuronal correlation of the variability in the activity of single neurons that were recorded simultaneously using a multielectrode array in the primary motor cortex and parietal areas 2/5 in rhesus monkeys. The animals were trained to move their arms in one of eight directions as instructed by a visual target. The relationship between variability (SD) and mean of the discharge rate was described by a power function with a similar exponent ( approximately 0.57), regardless of the cortical area or the behavioral condition. We examined whether the deviation from mean activity between target onset and the end of the movement was correlated on a trial-by-trial basis with variability in activity during the hold period before target onset. In both cortical areas, for about a quarter of the neurons, the neuronal noise of these two periods was positively correlated, whereas significant negative correlations were seldom observed. Overall, neurons with higher signal correlation (i.e., similar directional pattern) showed higher noise correlation in both cortical areas. On the other hand, when the data were divided according to the distance between the electrode tips from which the neurons were recorded, a consistent relationship between the signal and noise correlations was found only for pairs of neurons recorded through the same electrode. These results suggest that nearby neurons with similar directional tuning carry primarily redundant messages, whereas neurons in separate cortical columns perform more independent processing.     

Neuroimage of voluntary movement: topography of the Bereitschaftspotential, a 64-channel DC current source density study

The Bereitschaftspotential (BP) was recorded at 56 scalp positions when 17 healthy subjects performed brisk extensions of the right index finger. Aim of the study was to contribute to our understanding of the physiology underlying the BP and, in particular, to specify the situation at BP onset. For this purpose, the spatial pattern of the BP was analyzed in short time intervals (35 and/or 70 ms) starting 2.51 s before movement onset. For each time segment a spherical model of the BP was calculated by using spline interpolation. Then the spatial distribution of the electric potential at the scalp surface was transformed into a spatial distribution of current source densities (CSD map). Onset times of the BP and onset times of initial CSD-activity ranged between 2.23 and 1.81 s before movement onset. We selected a time window between 1.6 and 1.5 s before movement onset in order to analyze the spatial CSD pattern in each subject. In 10 subjects there was a significant current sink in the scalp area located over medial-wall motor areas (pre-SMA, SMA proper and anterior cingulate cortex: electrode positions C1, C2, FCz, Cz) in the absence of a significant current sink over the primary motor cortex (MI: electrode positions C3, CP3, and CP5). In three subjects significant current sinks were present at both sites and in another three subjects a current sink only over the lateral motor cortex was observed. In one subject no significant current sinks were measured. It is concluded that there is a large group of subjects (13/17) in whom BP at onset is associated with a current sink over medial-wall motor areas. At a later time interval (0.6 to 0.5 s before movement onset), significant current sinks were found in 13 subjects in medial and in 10 subjects in lateral recordings. These data were considered to be consistent with the hypothesis that, at least in a majority of subjects, medial-wall motor areas are activated earlier than lateral motor areas when organizing the initiation of a simple self-paced movement. Surface-recordings of the EEG do not allow further specification of cortical areas, which contribute to the current sinks. But in context with the current literature of the electrophysiology of nonhuman primates and of brain imaging in humans it is suggested that SMA and anterior cingulate cortex contribute to the current sink, the fronto-central midline, and that the primary motor cortex (MI) contributes to the current sink in the scalp area, which is located above MI and closely posterior to it.     

Evidence for direct connections between the hand region of the supplementary motor area and cervical motoneurons in the macaque monkey

In primates the corticospinal neurons of the hand representation of the primary motor cortex (M1) give rise to direct contacts with the cervical motoneurons that control distal forelimb muscles. We investigated, at the light-microscopy level, whether corticospinal cells present in the hand area of the supplementary motor area (SMA) also establish direct connections with cervical motoneurons, particularly those innervating hand and finger muscles. The hand representation of the M1 (two monkeys) or SMA (two monkeys) was located using intracortical microstimulation and injected with the anterograde tracer biotinylated dextran amine to label corticospinal terminals. Forearm muscles acting on the wrist and hand as well as hand muscles acting on the thumb and index finger, thus including those activated by intracortical stimulation, were injected with the retrograde tracer cholera-toxin B subunit, in order to label the motoneurons. A consistent zone of overlap between the two markers was found in the cervical cord. Close appositions between corticospinal axonal terminals and the somata or dendrites of motoneurons were found after injection in the M1, confirming previous observations. The new finding is the observation of similar close appositions after injection in the SMA, suggesting its control of hand movements in parallel with the M1.     

Sustained activity in the medial wall during working memory delays

We have taken advantage of the temporal resolution afforded by functional magnetic resonance imaging (fMRI) to investigate the role played by medial wall areas in humans during working memory tasks. We demarcated the medial motor areas activated during simple manual movement, namely the supplementary motor area (SMA) and the cingulate motor area (CMA), and those activated during visually guided saccadic eye movements, namely the supplementary eye field (SEF). We determined the location of sustained activity over working memory delays in the medial wall in relation to these functional landmarks during both spatial and face working memory tasks. We identified two distinct areas, namely the pre-SMA and the caudal part of the anterior cingulate cortex (caudal-AC), that showed similar sustained activity during both spatial and face working memory delays. These areas were distinct from and anterior to the SMA, CMA, and SEF. Both the pre-SMA and caudal-AC activation were identified by a contrast between sustained activity during working memory delays as compared with sustained activity during control delays in which subjects were waiting for a cue to make a simple manual motor response. Thus, the present findings suggest that sustained activity during working memory delays in both the pre-SMA and caudal-AC does not reflect simple motor preparation but rather a state of preparedness for selecting a motor response based on the information held on-line.     

Feline dental resorptive lesions

Bereitschaftspotentials (BPs) preceding simple repetitive finger movements were recorded in 11 normal volunteers. By modeling the recorded data with multiple equivalent dipoles we found that bilateral sources in the motor cortex were the best fitting hypothesis for the early BP. The activity of the source contralateral to the moving finger was increased during the steep slope of the late BP before and during the motor potential. Around and after electromyogram (EMG) onset, separate sources were detected for the motor potential close to the anterior wall of the central sulcus, and for the reafferent somatosensory potential in the postcentral gyrus. Their source wave forms showed short transient deflections peaking about 10 msec and 100 msec, respectively, after EMG onset. No evidence was found for significant source currents in the supplementary motor area (SMA), which has been suggested as the main generator of the BP. Placing probe dipoles arbitrarily into the region of the SMA did not result in the detection of a large source activity. Therefore, we conclude that the SMA does not provide a major contribution to the scalp BP during simple repetitive finger movements.     

Ser-311-Cys polymorphism of the dopamine D2 receptor gene and schizophrenia--an analysis of schizophrenic patients in Fukuoka

Functional brain imaging studies have indicated that several cortical and subcortical areas active during actual motor performance are also active during imagination or mental rehearsal of movements. Recent evidence shows that the primary motor cortex may also be involved in motor imagery. Using whole-scalp magnetoencephalography, we monitored spontaneous and evoked activity of the somatomotor cortex after right median nerve stimuli in seven healthy right-handed subjects while they kinesthetically imagined or actually executed continuous finger movements. Manipulatory finger movements abolished the poststimulus 20-Hz activity of the motor cortex and markedly affected the somatosensory evoked response. Imagination of manipulatory finger movements attenuated the 20-Hz activity by 27% with respect to the rest level but had no effect on the somatosensory response. Slight constant stretching of the fingers suppressed the 20-Hz activity less than motor imagery. The smallest possible, kinesthetically just perceivable finger movements resulted in slightly stronger attenuation of 20-Hz activity than motor imagery did. The effects were observed in both hemispheres but predominantly contralateral to the performing hand. The attempt to execute manipulatory finger movements under experimentally induced ischemia causing paralysis of the hand also strongly suppressed 20-Hz activity but did not affect the somatosensory evoked response. The results indicate that the primary motor cortex is involved in motor imagery. Both imaginative and executive motor tasks appear to utilize the cortical circuitry generating the somatomotor 20-Hz signal.     

Spontaneous motor activity in fetal and infant rats is organized into discrete multilimb bouts.

Spontaneous motor activity (SMA) is a ubiquitous feature of fetal and infant behavior. Although SMA appears random, successive limb movements often occur in bouts. Bout organization was evident at all ages in fetal (embryonic day [E] 17–21) and infant (postnatal day [P] 1–9) rats, with nearly all bouts comprising 1–4 movements of different limbs. A computational model of SMA, including spontaneous activity of spinal motor neurons, intrasegmental and intersegmental interactions, recurrent inhibition, and descending influences, produced bouts with the same structure as that observed in perinatal rats. Consistent with the model, bouts were not eliminated on E20 after cervical spinal transection, suggesting that the brain is not necessary to produce bout organization. These investigations provide a foundation for understanding the contributions of SMA to neuromuscular and motor development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Handedness and asymmetry of hand representation in human motor cortex

The cortical representation of five simple hand and finger movements in the human motor cortex was determined in left- and right-handed people with whole-head magnetoencephalography. Different movements were found to be represented by spatially segregated dipolar sources in primary motor cortex. The spatial arrangement of neuronal sources for digit and wrist movements was nonsomatotopic and varied greatly between subjects. As an estimator of hand area size in primary motor cortex, we determined the smallest cuboid volume enclosing the five dipole sources within the left and right hemisphere of each subject. Interhemispheric comparison revealed a significant increase of this volume in primary motor cortex opposite to the preferred hand. This asymmetry was due to a greater spatial segregation of neuronal dipole generators subserving different hand and finger actions in the dominant hemisphere. Mean Euclidean distances between dipole sources for different movements were 10.7 +/- 3.5 mm in the dominant and 9.4 +/- 3.5 mm in the nondominant hemisphere (mean +/- SD; P = 0. 01, two-tailed t-test). The expansion of hand representation in primary motor cortex could not simply be attributed to a greater number of pyramidal cells devoted to each particular movement as inferred from current source amplitudes. The degree of hemispheric asymmetry of hand area size in the primary motor cortex was correlated highly with the asymmetry of hand performance in a standardized handedness test (r = -0.76, P < 0.01). These results demonstrate for the first time a biological correlate of handedness in human motor cortex. The expansion of hand motor cortex in the dominant hemisphere may provide extra space for the cortical encoding of a greater motor skill repertoire of the preferred hand.     

Eye position influence on the parieto-occipital area PO (V6) of the macaque monkey

The aim of this work was to study the effect of eye position on the activity of neurons of area PO (V6), a cortical region located in the most posterior part of the superior parietal lobule. Experiments were carried out on three awake macaque monkeys. Animals sat in a primate chair in front of a large screen, and fixated a small spot of light projected in different screen locations while the activity of single neurons was extracellularly recorded. Both visual and non-visual neurons were found. About 48% of visual and 32% of non-visual neurons showed eye position-related activity in total darkness, while in approximately 61% of visual response was modulated by eye position in the orbit. Eye position fields and/or gain fields were different from cell to cell, going from large and quite planar fields up to peak-shaped fields localized in more or less restricted regions of the animal's field of view. The spatial distribution of fixation point locations evoking peak activity in the eye position-sensitive population did not show any evident laterality effect, or significant top/bottom asymmetry. Moreover, the cortical distribution of eye position-sensitive neurons was quite uniform all over the cortical region studied, suggesting the absence of segregation for this property within area PO (V6). In the great majority of visual neurons, the receptive field 'moved' with gaze according to eye displacements, remaining at the same retinotopic coordinates, as is usual for visual neurons. In some cases, the receptive field did not move with gaze, remaining anchored to the same spatial location regardless of eye movements ('real-position cells'). A model is proposed suggesting how eye position-sensitive visual neurons might build up real-position cells in local networks within area PO (V6). The presence in area PO (V6) of real-position cells together with a high percentage of eye position-sensitive neurons, most of them visual in nature, suggests that this cortical area is engaged in the spatial encoding of extrapersonal visual space. Since lesions of the superior parietal lobule in humans produce deficits in visual localization of targets as well as in arm-reaching for them, and taking into account that the monkey's area PO (V6) is reported to be connected with the premotor area 6, we suggest that area PO (V6) supplies the premotor cortex with the visuo-spatial information required for the visual control of arm-reaching movements.     

Motor prediction at the edge of instability: Alteration of grip force control during changes in bimanual coordination.

Predicting the consequences of actions is fundamental for skilled motor behavior. We investigated whether motor prediction is influenced by the fact that some movements are easier to perform and stabilize than others. Twelve subjects performed a bimanual rhythmical task either symmetrically or asymmetrically (the latter being more difficult and less stable) while oscillating in each hand an object attached to an elastic cord. Motor prediction was monitored through the adequacy of anticipatory grip force adjustments with respect to the elastic resisting force. Results showed less adequate predictive control during asymmetrical movements (compared with symmetrical ones). Furthermore, switching between modes of coordination induced even larger alterations. An interesting finding was that grip force control did not always stabilize around the expected value after voluntary transition. We conclude that motor prediction is affected by the degree of coordination between the upper limbs and by phase transitions and is prone to carryover effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)