Impaired control of an action after supplementary motor area lesion: a case study

Neural predictors of motor control and impact of visuo-proprioceptive information in youth

For successful motor control, the central nervous system is required to combine information from the environment and the current body state, which is provided by vision and proprioception respectively. We investigated the relative contribution of visual and proprioceptive information to upper limb motor control and the extent to which structural brain measures predict this performance in youth (n = 40; age range 9-18 years). Participants performed a manual tracking task, adopting in-phase and anti-phase coordination modes. Results showed that, in contrast to older participants, younger participants performed the task with lower accuracy in general and poorer performance in anti-phase than in-phase modes. However, a proprioceptive advantage was found at all ages, that is, tracking accuracy was higher when proprioceptive information was available during both in- and anti-phase modes at all ages. The microstructural organization of interhemispheric connections between homologous dorsolateral prefrontal cortices, and the cortical thickness of the primary motor cortex were associated with sensory-specific accuracy of tracking performance. Overall, the findings suggest that manual tracking performance in youth does not only rely on brain regions involved in sensorimotor processing, but also on prefrontal regions involved in attention and working memory. Hum Brain Mapp 38:5628-5647, 2017. © 2017 Wiley Periodicals, Inc.

Shared timing variability in eye and finger movements increases with interval duration: Support for a distributed timing system below and above one second

The origins of the ability to produce action at will at the hundreds of millisecond to second range remain poorly understood. A central issue is whether such timing is governed by one mechanism or by several different mechanisms, possibly invoked by different effectors used to perform the timing task. If two effectors invoke similar timing mechanisms, then they should both produce similar variability increase with interval duration (interonset interval) and thus adhere to Weber's law (increasing linearly with the duration of the interval to be timed). Additionally, if both effectors invoke the same timing mechanism, the variability of the effectors should be highly correlated across participants. To test these possibilities, we assessed the behavioural characteristics across fingers and eyes as effectors and compared the timing variability between and within them as a function of the interval to be produced (interresponse interval). Sixty participants produced isochronous intervals from 524 to 1431 ms with their fingers and their eyes. High correlations within each effector indicated consistent performance within participants. Consistent with a single mechanism, temporal variability in both fingers and eyes followed Weber's law, and significant correlations between eye and finger variability were found for several intervals. These results can support neither the single clock nor the multiple clock hypotheses but instead suggest a partially overlapping distributed timing system.

Two-dimensional representation of action and arm-use sequences in the presupplementary and supplementary motor areas

The medial frontal cortex has been thought to be crucially involved in temporal structuring of behavior in monkeys and humans. We examined neuronal activity in the supplementary and presupplementary motor areas of monkeys to investigate how the nervous system deals with the coding of 16 motor sequences resulting from multiple actions involving bilateral use of the arms. We first found in both areas that this behavioral demand resulted in attribute-based representation of individual motor acts, reflecting functional (action) or anatomical (right/left arm) attributes. Actions were frequently represented according to a body-axis-centered reference frame (supination or pronation) regardless of the arm to be used. Moreover, behavioral sequences were primarily represented with respect to the action- or arm-use sequence rather than the sequence of individual movements. We propose that the two-dimensional attribute-based sequence representation provides a robust and efficient means of processing multiple behavioral sequences.

Posterior SMA Syndrome following subcortical stroke: contralateral akinesia reversed by visual feedback

BACKGROUND

The supplementary motor area (SMA) plays a key role in motor programming and production and is involved in internally-cued movements. In neurological populations, SMA syndrome following a lesion to the "SMA proper" is characterized by transient impairment of voluntary movements and motor sequences. This syndrome is assumed to follow on from an interruption of the motor cortico-subcortical loop, and some case reports indicate that such a syndrome could occur after a brain lesion isolating the SMA from subcortical structures.

AIM

To characterize the pattern of motor impairments in a patient whose stroke disconnects the SMA from the subcortical motor loop.

METHOD

A patient developed a moderate transient left hemiparesis following a subcortical stroke in the right anterior cerebral artery area, which disconnected the SMA from basal ganglia. Eight days after the stroke, when the hemiparesis had regressed, the patient presented a specific SMA motor disorder of the left hand which manifested as an akinesia and was exacerbated when his visual attention was not directed towards his hand. We assessed finger tapping with left and right hands, eyes closed and open, in the left and right hemispace. We indexed movement speed as the number of taps filmed over 5-s periods.

RESULTS

Left motor weakness (grasping strength of right hand: 49 kg and left hand: 41 kg) was resolved in a week. Ideomotor and ideational gestures and motor sequences were preserved. On the tapping task, left-hand tapping was slower than right-hand tapping. Critically, visual feedback improved tapping speed for the left, but not for the right, hand. The hemispace of the task execution had no effect on tapping performance.

CONCLUSION

Our results suggest that SMA-basal ganglia disconnection decreases contralateral movement initiation and maintenance and this effect is partly compensated by visual cues.

ALE meta-analysis of action observation and imitation in the human brain

Over the last decade, many neuroimaging studies have assessed the human brain networks underlying action observation and imitation using a variety of tasks and paradigms. Nevertheless, questions concerning which areas consistently contribute to these networks irrespective of the particular experimental design and how such processing may be lateralized remain unresolved. The current study aimed at identifying cortical areas consistently involved in action observation and imitation by combining activation likelihood estimation (ALE) meta-analysis with probabilistic cytoarchitectonic maps. Meta-analysis of 139 functional magnetic resonance and positron emission tomography experiments revealed a bilateral network for both action observation and imitation. Additional subanalyses for different effectors within each network revealed highly comparable activation patterns to the overall analyses on observation and imitation, respectively, indicating an independence of these findings from potential confounds. Conjunction analysis of action observation and imitation meta-analyses revealed a bilateral network within frontal premotor, parietal, and temporo-occipital cortex. The most consistently rostral inferior parietal area was PFt, providing evidence for a possible homology of this region to macaque area PF. The observation and imitation networks differed particularly with respect to the involvement of Broca's area: whereas both networks involved a caudo-dorsal part of BA 44, activation during observation was most consistent in a more rostro-dorsal location, i.e., dorsal BA 45, while activation during imitation was most consistent in a more ventro-caudal aspect, i.e., caudal BA 44. The present meta-analysis thus summarizes and amends previous descriptions of the human brain networks related to action observation and imitation.

The neural substrates for atypical planning and execution of word production in stuttering

Using an fMRI-based classification approach and the structural equation modeling (SEM) method, this study examined the neural bases of atypical planning and execution processes involved in stuttering. Twelve stuttering speakers and 12 controls were asked to name pictures under different conditions (single-syllable, multi-syllable, or repeated-syllable) in the scanner. The contrasts between conditions provided information about planning and execution processes. The classification analysis showed that, as compared to non-stuttering controls, stuttering speakers' atypical planning of speech was evident in their neural activities in the bilateral inferior frontal gyrus (IFG) and right putamen and their atypical execution of speech was evident in their activations in the right cerebellum and insula, left premotor area (PMA), and angular gyrus (AG). SEM results further revealed two parallel neural circuits-the basal ganglia-IFG/PMA circuit and the cerebellum-PMA circuit-that were involved in atypical planning and execution processes of stuttering, respectively. The AG appeared to be involved in the interface of atypical planning and execution in stuttering. These results are discussed in terms of their implications to the theories about stuttering and to clinical applications.

Effects of timing and movement uncertainty implicate the temporo-parietal junction in the prediction of forthcoming motor actions

The concept of predictive coding supposes the brain to build predictions of forthcoming events in order to decrease the computational load, thereby facilitating efficient reactions. In contrast, increasing uncertainty, i.e., lower predictability, should increase reaction time and neural activity due to reactive processing and believe updating. We used functional magnetic resonance imaging (fMRI) to scan subjects reacting to briefly presented arrows pointing to either side by pressing a button with the corresponding index finger. Predictability of these stimuli was manipulated along the independently varied factors "response type" (known hand or random, i.e., unknown order) and "timing" (fixed or variable intervals between stimuli). Behavioural data showed a significant reaction-time advantage when either factor was predictable, confirming the hypothesised reduction in computational load. On the neural level, only the right temporo-parietal junction showed enhanced activation upon both increased task and timing uncertainty. Moreover, activity in this region also positively correlated with reaction time. There was, however, a dissociation between both factors in the frontal lobe, as increased timing uncertainty recruited right BA 44, whereas increased response uncertainty activated the right ventral premotor cortex, the pre-SMA and the DLPFC. In line with the theoretical framework of predictive coding as a load-saving mechanism no brain region showed significantly increased activity in the lower uncertainty conditions or correlated negatively with reaction times. This study hence provided behavioural and neuroimaging evidence for predictive motor coding and points to a key role of the right temporo-parietal junction in its implementation.

Motor and language deficits before and after surgical resection of mesial frontal tumour

OBJECTIVE

The goal of the present study was to better characterize pre- and immediately post-surgical motor and language deficits resulting from the surgery of tumours located in the medial part of the frontal lobe.

PATIENTS AND METHODS

Seven patients treated by surgical resection of low-grade gliomas affecting the medial part of the frontal lobe were studied with neuropsychological tasks investigating motor and language abilities before surgery and at three time points after surgery (first, third and seventh day after surgery). The tasks were constructed in a way that allowed the structured comparison between language and motor functions, and controlled the level of external constraint of the production.

RESULTS

The main results of this study are: (1) globally the patients were impaired in both language and motor production the day after surgery; (2) the performance improved faster for tasks with strongly constrained production; (3) the verbal and semantic fluency were very sensitive and appropriate tasks for examination of the deficits resulting from the resection; and (4) performances were back to normal seven days after the surgery for most of the tasks.

CONCLUSION

These results confirm that surgery of low-grade gliomas affecting the prefrontal midline areas affects only transiently motor and language functions as tested in this study. They also suggest that verbal and semantic fluency were the most severely affected tests postoperatively. On the basis of these results, the surgical resection of the low-grade gliomas of the prefrontal midline seems a valuable treatment alternative.

Evidence for a distributed hierarchy of action representation in the brain

Complex human behavior is organized around temporally distal outcomes. Behavioral studies based on tasks such as normal prehension, multi-step object use and imitation establish the existence of relative hierarchies of motor control. The retrieval errors in apraxia also support the notion of a hierarchical model for representing action in the brain. In this review, three functional brain imaging studies of action observation using the method of repetition suppression are used to identify a putative neural architecture that supports action understanding at the level of kinematics, object centered goals and ultimately, motor outcomes. These results, based on observation, may match a similar functional-anatomic hierarchy for action planning and execution. If this is true, then the findings support a functional-anatomic model that is distributed across a set of interconnected brain areas that are differentially recruited for different aspects of goal-oriented behavior, rather than a homogeneous mirror neuron system for organizing and understanding all behavior.

Altered coordination patterns in parkinsonian patients during trunk-assisted prehension

We examined whether coordination between movement components during trunk-assisted prehension was compromised in PD patients in response to varying constraints (experiment 1: reach speed, object size, movement amplitude; experiment 2: movement sequence). In general, both PD patients and controls responded similarly to the changes in these three variables. PD patients, however, demonstrated less synchronized movements in terms of timing between onsets and offsets of aperture formation, endpoint motion and trunk motion. In addition, PD patients used a pattern different from that of controls in specifying the relative contribution of trunk and arm to the endpoint motion. A significant group difference was observed in that controls tended to synchronize the involved movement components together, whereas PD patients did not show such a trend. These data suggest that PD patients have intact parameterization capabilities, although they have a reduced capability to coordinate multiple neuromotor synergies as a single unit.

The effects of constraint-induced therapy on precision grip: a preliminary study

OBJECTIVE

This preliminary study examines the effects of a 2-week constraint-induced therapy (CIT) intervention on the force-producing capabilities of the hemiparetic hand during the performance of a functional dexterous manipulation task.

METHODS

A 6-degree-of-freedom force/torque transducer that was embedded into the handle of a key allowed for the quantification of grasping forces and torques produced during the performance of a functional key-turning task. Clinical and kinetic data were collected from 10 subacute patients (3-9 months poststroke) who were participating in an ongoing national clinical study (EXCITE trial) examining the effects of CIT on upper extremity motor performance. Investigators were blinded to treatment designation. Five patients receiving treatment immediately completed 2 weeks of intensive CIT, whereas a group randomized to treatment 1 year later did not receive any therapy during a similar 2-week span.

RESULTS

. Results indicated that 4 of the 5 patients in the CIT group, compared to the delayed group, showed significant clinical improvements in hand function, increased maximum precision grip force, improved force and torque regulation, and reduced variability in rate of force production during task performance.

CONCLUSIONS

Improved force control may be a mechanism contributing to the observed improvements in dexterous function in those patients undergoing CIT.

Effects of disease progression and L-dopa therapy on the control of reaching-grasping in Parkinson's disease

The present study aimed to determine whether the bradykinesia of Parkinson's disease (PD) patients during the execution of reaching-grasping movements (i) is related to an impaired implementation of movement parameters and (ii) selectively involves the control of reach and/or grasp movements. We compared the kinematics of reaching to grasp of differently sized objects placed at different positions, among PD patients in the early stage of disease (ESPD), in the advanced stage of disease (ASPD) without L-dopa medication (off-state), and in healthy controls. In addition, we analysed the effects of L-dopa replacement therapy by comparing the kinematics of the patients in the advanced stage of disease after L-dopa administration with those of the other groups. Bradykinesia increased with disease progression, but only in the initial phases of the reach and grasp components. However at both stages of the disease, the kinematics of reaching and grasping responded to extrinsic and intrinsic object properties just as in controls. L-dopa administration improved the performance of PD patients, though this was more evident for the reach than for the grasp. We suggest that the basal ganglia (BG) are involved in implementing kinematic parameters, but neither (or only marginally) in the initial movement parameterization itself, nor in the on-line control of movement. Specifically, the BG dysfunction in PD induces a slowed implementation of movement parameters. The lack of effect of L-dopa administration on grasp kinematics may be because the motor control of distal effectors is less represented in the motor circuitry formed by the supplementary motor area (SMA), thalamus and BG.

Compensation for distal impairments of grasping in adults with hemiparesis

Previous studies have shown that patients with arm and hand paresis following stroke recruit an additional degree of freedom (the trunk) to transport the hand during reaching and use alternative strategies for grasping. The few studies of grasping parameters of the impaired hand have been case studies mainly focusing on describing grasping in the presence of particular impairments such as hemi-neglect or optic ataxia and have not focussed on the role of the trunk in prehension. We hypothesized that the trunk movement not only ensures the transport of the hand to the object, but it also assists in orienting the hand for grasping when distal deficits are present. Nineteen patients with chronic hemiparesis and seven healthy subjects participated in the study. Patients had sustained a stroke of non-traumatic origin 6-82 months previously (31+/-22 months) and had mild or moderate to severe arm paresis. Using a whole hand grasp, subjects reached and grasped a cylinder (35 mm) that was placed sagittally (T1) or at a 45 degrees angle to the sagittal midline in the ipsilateral workspace (T2), both at about 90% arm's length (10 trials per target). Eight infrared emitting diodes were placed on bony landmarks of the hand, arm and trunk and kinematic data were recorded by an optical motion analysis system (Optotrak) for 2-5 s at 120 Hz. Hand position and orientation were recorded by a Fastrack Polhemus system. Our results show that during goal-directed prehension tasks, individuals with hemiparesis oriented the hand more frontally for grasping and used more trunk anterior displacement or rotation to transport the hand to the target compared to healthy subjects. Despite these changes, the major characteristics of reaching and grasping such as grip aperture size, temporal coordination between hand transport and aperture formation and the relative timing of grip aperture were largely preserved. For patients with more severe distal impairments, the amount of trunk displacement was also correlated with a more frontal hand orientation for grasping. Furthermore, in healthy subjects and patients without distal impairments, the trunk movement was mostly related to proximal arm movements while in those with distal impairments, trunk movement was related to both proximal and distal arm movements. Data support the hypothesis that the trunk movement is used to assist both arm transport and hand orientation for grasping when distal deficits are present.

Advance movement preparation of eye, foot, and hand: a comparative study using movement-related brain potentials

The present study was designed to test the inter-relationship between generalized motor programs (GMPs) and movement preparation by asking participants to perform movements with eye, foot, or hand. In two independent experiments a response precuing task was employed that combined the recording of movement-related brain potentials (MRPs) with dipole source analysis. Behavioral results indicated the utilization of advance information about movement direction and effector. When eye and hand movements were involved (experiment1) partial advance information about response side but not effector induced parallel motor programming of eye and hand at an abstract but not effector-specific level. In contrast, when partial precues specified side of a forthcoming hand or foot movement (experiment 2) foot and hand were prepared in parallel both at abstract and at effector-specific levels of motor programming. Consistent with the GMP view, these results indicate that effector-specific preparation is possible even when the effector is not yet known as long as a common motor program controls the demanded movements. However, because parallel specification of divergent movement pattern (eye, hand) at an abstract level was not predicted by the GMP, we propose a model of advance movement preparation that takes into account neurofunctional considerations.

Utilisation behaviour consequent to bilateral SMA softening

The case of patient CU, who presented with severe utilisation behaviour, eventually unaccompanied by psychometric signs of frontal involvement, is reported. He suffered from a bilateral stroke within the territory of the anterior cerebral artery. His arterial system was characterised by a unique variant, whereby the right anterior cerebral artery was missing and three trunks originated from the left anterior cerebral artery, each bifurcating into right and left branches. An occlusion of the middle trunk immediately before its partition gave rise to a symmetrical bilateral parasagittal lesion that damaged the supplementary motor areas (medial part of Brodmann's area 6), sparing the lateral regions including the premotor cortices, the corpus callosum and the gyri cinguli. The hypothesis is put forward that utilisation behaviour should be conceived as a double anarchic hand, and its interpretation should rest on the damaged balance between the premotor cortices, responsive to environmental triggers, and the supplementary motor areas, which modulate actions and inhibit them. The imbalance due to the lesion would result in the patients being left at the mercy of environmental stimuli, unable to inhibit inappropriate actions. This intra-frontal hypothesis accounts for the data presented and those from the literature better than the previously held fronto-parietal equipoise.

Visual control of isometric force in Parkinson's disease

The current article reports an investigation of the influence of visual feedback on force production in Parkinson's disease (PD) that required subjects to maintain a constant amount of isometric force with their index finger and thumb with and without visual feedback. Eight PD and eight matched control subjects produced force at 5, 25 and 50% of their maximal voluntary contraction for 20 s. In conditions of full vision, the force trajectory and force target were viewed on the computer monitor. In the no visual feedback condition, visual feedback of the force trajectory vanished after the initial 8 s of the trial. The results showed that under the vision condition PD subjects produced levels of maximal and submaximal force that were similar to controls. Approximately 1.5-2.5 s following the removal of visual feedback, the force level in both subject groups decreased to steady-state levels. There was no difference in the time between visual feedback removal and the beginning of force decay in PD. There was a larger amount and faster rate of force decay after visual feedback removal in PD subjects compared to the controls. It is proposed that the increased force decay in PD does not result from sensory reflex deficits but from higher order sensory-motor memory processes.