Identification of multiple nonprimary motor cortical areas with simple movements

Two Distinct Systems Represent Contralateral and Ipsilateral Sensorimotor Processes in the Human Premotor Cortex: A Dense TMS Mapping Study

Animal brains contain behaviorally committed representations of the surrounding world, which integrate sensory and motor information. In primates, sensorimotor mechanisms reside in part in the premotor cortex (PM), where sensorimotor neurons are topographically clustered according to functional specialization. Detailed functional cartography of the human PM is still under investigation. We explored the topographic distribution of spatially dependent sensorimotor functions in healthy volunteers performing left or right, hand or foot, responses to visual cues presented in the left or right hemispace, thus combining independently stimulus side, effector side, and effector type. Event-related transcranial magnetic stimulation was applied to single spots of a dense grid of 10 points on the participants' left hemiscalp, covering the whole PM. Results showed: (1) spatially segregated hand and foot representations, (2) focal representations of contralateral cues and movements in the dorsal PM, and (3) distributed representations of ipsilateral cues and movements in the ventral and dorso-medial PM. The present novel causal information indicates that (1) the human PM is somatotopically organized and (2) the left PM contains sensory-motor representations of both hemispaces and of both hemibodies, but the hemispace and hemibody contralateral to the PM are mapped on a distinct, nonoverlapping cortical region compared to the ipsilateral ones.

Impairment and Compensation in Dexterous Upper-Limb Function After Stroke. From the Direct Consequences of Pyramidal Tract Lesions to Behavioral Involvement of Both Upper-Limbs in Daily Activities

Impairments in dexterous upper limb function are a significant cause of disability following stroke. While the physiological basis of movement deficits consequent to a lesion in the pyramidal tract is well demonstrated, specific mechanisms contributing to optimal recovery are less apparent. Various upper limb interventions (motor learning methods, neurostimulation techniques, robotics, virtual reality, and serious games) are associated with improvements in motor performance, but many patients continue to experience significant limitations with object handling in everyday activities. Exactly how we go about consolidating adaptive motor behaviors through the rehabilitation process thus remains a considerable challenge. An important part of this problem is the ability to successfully distinguish the extent to which a given gesture is determined by the neuromotor impairment and that which is determined by a compensatory mechanism. This question is particularly complicated in tasks involving manual dexterity where prehensile movements are contingent upon the task (individual digit movement, grasping, and manipulation…) and its objective (placing, two step actions…), as well as personal factors (motivation, acquired skills, and life habits…) and contextual cues related to the environment (presence of tools or assistive devices…). Presently, there remains a lack of integrative studies which differentiate processes related to structural changes associated with the neurological lesion and those related to behavioral change in response to situational constraints. In this text, we shall question the link between impairments, motor strategies and individual performance in object handling tasks. This scoping review will be based on clinical studies, and discussed in relation to more general findings about hand and upper limb function (manipulation of objects, tool use in daily life activity). We shall discuss how further quantitative studies on human manipulation in ecological contexts may provide greater insight into compensatory motor behavior in patients with a neurological impairment of dexterous upper-limb function.

Neural correlates of visuomotor adjustments during scaling of human finger movements

Visually guided finger movements include online feedback of current effector position to guide target approach. This visual feedback may be scaled or otherwise distorted by unpredictable perturbations. Although adjustments to visual feedback scaling have been studied before, the underlying brain activation differences between upscaling (visual feedback larger than real movement) and downscaling (feedback smaller than real movement) are currently unknown. Brain activation differences between upscaling and downscaling might be expected because within-trial adjustments during upscaling require corrective backwards accelerations, whereas correcting for downscaling requires forward accelerations. In this behavioural and fMRI study we investigated adjustments during up- and downscaling in a target-directed finger flexion-extension task with real-time visual feedback. We found that subjects made longer and more complete within-trial corrections for downscaling perturbations than for upscaling perturbations. The finger task activated primary motor (M1) and somatosensory (S1) areas, premotor and parietal regions, basal ganglia, and cerebellum. General scaling effects were seen in the right pre-supplementary motor area, dorsal anterior cingulate cortex, inferior parietal lobule, and dorsolateral prefrontal cortex. Stronger activations for down- than for upscaling were observed in M1, supplementary motor area (SMA), S1 and anterior cingulate cortex. We argue that these activation differences may reflect differing online correction for upscaling vs. downscaling during finger flexion-extension.

[Brain plasticity: limitations and possibilities]

Biological limitations related to the brain regeneration and stem cells transplantation as well as the factors influencing the brain plasticity following the brain injury, including epigenetic regulatory mechanisms, are presented. Non-invasive transcranial microelectrostimulation is considered as a perspective method of polysystemic influence on endogenic mechanisms of brain recovery.

Rhythmic brain stimulation reduces anxiety-related behavior in a mouse model based on meditation training

Meditation training induces changes at both the behavioral and neural levels. A month of meditation training can reduce self-reported anxiety and other dimensions of negative affect. It also can change white matter as measured by diffusion tensor imaging and increase resting-state midline frontal theta activity. The current study tests the hypothesis that imposing rhythms in the mouse anterior cingulate cortex (ACC), by using optogenetics to induce oscillations in activity, can produce behavioral changes. Mice were randomly assigned to groups and were given twenty 30-min sessions of light pulses delivered at 1, 8, or 40 Hz over 4 wk or were assigned to a no-laser control condition. Before and after the month all mice were administered a battery of behavioral tests. In the light/dark box, mice receiving cortical stimulation had more light-side entries, spent more time in the light, and made more vertical rears than mice receiving rhythmic cortical suppression or no manipulation. These effects on light/dark box exploratory behaviors are associated with reduced anxiety and were most pronounced following stimulation at 1 and 8 Hz. No effects were seen related to basic motor behavior or exploration during tests of novel object and location recognition. These data support a relationship between lower-frequency oscillations in the mouse ACC and the expression of anxiety-related behaviors, potentially analogous to effects seen with human practitioners of some forms of meditation.

The effect of motor familiarity during simple finger opposition tasks

Humans are more familiar with performing (and observing) index-thumb than with any other finger to thumb grasping and the effect of familiarity has not been tested specifically with simple and intransitive actions. The study of simple and intransitive motor actions (i.e. simple actions without need of object interaction) provides the opportunity to investigate specifically the brain motor regions reducing the effect of non-motor aspects that are related with more complex and/or transitive motor actions. The aim of this study is to evaluate brain activity patterns during the execution of simple and intransitive finger movements with different degrees of familiarity. With this in mind, a functional Magnetic Resonance Imaging (fMRI) study was performed in which participants were asked to execute finger to thumb opposition tasks with all the different fingers (index, middle, ring and little) with a fixed frequency (1 Hz) determined by a visual cue. This movement is considered as the pantomime of a precision grasping action. Significant activity was identified in the Sensory Motor Cortex (SMC), posterior parietal and premotor regions for all simple conditions (index-finger>control, middle-finger>control, ring-finger>control and little-finger>control). However, a linear trend contrast (index<middle<ring<little) demonstrated that there was a linear increase of activity in the SMC (mainly in the Precentral Gyrus) while the finger used to perform the action was further from the thumb. Therefore, the execution of less familiar simple intransitive movements seems to lead to a stronger activation of the SMC than familiar ones. Posterior parietal and premotor regions did not show the aforementioned stronger activation. The most important implication of this study is the identification of differences in brain activity during the execution of simple intransitive movements with different degrees of familiarity.

Area- and band-specific representations of hand movements by local field potentials in caudal cingulate motor area and supplementary motor area of monkeys

The caudal cingulate motor area (CMAc) and the supplementary motor area (SMA) play important roles in movement execution. The present study examined the neural mechanisms underlying these roles by investigating local field potentials (LFPs) from these areas while monkeys pressed buttons with either their left or right hand. During hand movement, power increases in the high-gamma (80-120 Hz) and theta (3-8 Hz) bands and a power decrease in the beta (12-30 Hz) band were observed in both the CMAc and SMA. High-gamma and beta activity in the SMA predominantly represented contralateral hand movements, whereas activity in the CMAc preferentially represented movement of either hand. Theta activity in both brain regions most frequently reflected movement of either hand, but a contralateral hand bias was more evident in the SMA than in the CMAc. An analysis of the relationships of the laterality representations between the high-gamma and theta bands at each recording site revealed that, irrespective of the hand preference for the theta band, the high-gamma band in the SMA preferentially represented contralateral hand movement, whereas the high-gamma band in the CMAc represented movement of either hand. These findings suggest that the input-output relationships for ipsilateral and contralateral hand movements in the CMAc and SMA differ in terms of their functionality. The CMAc may transform the input signals representing general aspects of movement into commands to perform movements with either hand, whereas the SMA may transform the input signals into commands to perform movement with the contralateral hand.

Distinct neuronal organizations of the caudal cingulate motor area and supplementary motor area in monkeys for ipsilateral and contralateral hand movements

The caudal cingulate motor area (CMAc) and the supplementary motor area (SMA) play important roles in movement execution. The present study aimed to characterize the functional organization of these regions during movement by investigating laterality representations in the CMAc and SMA of monkeys via an examination of neuronal activity during a button press movement with either the right or left hand. Three types of movement-related neuronal activity were observed: 1) with only the contralateral hand, 2) with only the ipsilateral hand, and 3) with either hand. Neurons in the CMAc represented contralateral and ipsilateral hand movements to the same degree, whereas neuronal representations in the SMA were biased toward contralateral hand movement. Furthermore, recording neuronal activities using a linear-array multicontact electrode with 24 contacts spaced 150 μm apart allowed us to analyze the spatial distribution of neurons exhibiting particular hand preferences at the submillimeter scale. The CMAc and SMA displayed distinct microarchitectural organizations. The contralateral, ipsilateral, and bilateral CMAc neurons were distributed homogeneously, whereas SMA neurons exhibiting identical hand preferences tended to cluster. These findings indicate that the CMAc, which is functionally organized in a less structured manner than the SMA is, controls contralateral and ipsilateral hand movements in a counterbalanced fashion, whereas the SMA, which is more structured, preferentially controls contralateral hand movements.

Sleepwalking episodes are preceded by arousal-related activation in the cingulate motor area: EEG current density imaging

OBJECTIVE

To investigate local arousal fluctuations in adults who received ICSD-2 diagnosis of somnambulism.

METHODS

EEG neuroimaging (eLORETA) was utilized to compare current density distribution for 4s epochs immediately preceding sleepwalking episode (from -4.0 s to 0 s) to the distribution during earlier 4s epochs (from -8.0 s to -4.0 s) in 20 EEG segments from 15 patients.

RESULTS

Comparisons between eLORETA images revealed significant (t>4.52; p<0.05) brain activations before onset of sleepwalking, with greater current density within beta 3 frequency range (24-30 Hz) in Brodmann areas 33 and 24.

CONCLUSIONS

Sleepwalking motor events are associated with arousal-related activation of cingulate motor area.

SIGNIFICANCE

These results support the notion of blurred boundaries between wakefulness and NREM sleep in sleepwalking.

Observation of simple intransitive actions: the effect of familiarity

Introduction

Humans are more familiar with index – thumb than with any other finger to thumb grasping. The effect of familiarity has been previously tested with complex, specialized and/or transitive movements, but not with simple intransitive ones. The aim of this study is to evaluate brain activity patterns during the observation of simple and intransitive finger movements with differing degrees of familiarity.

Methodology

A functional Magnetic Resonance Imaging (fMRI) study was performed using a paradigm consisting of the observation of 4 videos showing a finger opposition task between the thumb and the other fingers (index, middle, ring and little) in a repetitive manner with a fixed frequency (1 Hz). This movement is considered as the pantomime of a precision grasping action.

Results

Significant activity was identified in the bilateral Inferior Parietal Lobule and premotor regions with the selected level of significance (FDR [False Discovery Rate] = 0.01). The extent of the activation in both regions tended to decrease when the finger that performed the action was further from the thumb. More specifically, this effect showed a linear trend (index>middle>ring>little) in the right parietal and premotor regions.

Conclusions

The observation of less familiar simple intransitive movements produces less activation of parietal and premotor areas than familiar ones. The most important implication of this study is the identification of differences in brain activity during the observation of simple intransitive movements with different degrees of familiarity.

A Bayesian approach for characterizing direction tuning curves in the supplementary motor area of behaving monkeys

Neural responses are commonly studied in terms of "tuning curves," characterizing changes in neuronal response as a function of a continuous stimulus parameter. In the motor system, neural responses to movement direction often follow a bell-shaped tuning curve for which the exact shape determines the properties of neuronal movement coding. Estimating the shape of that tuning curve robustly is hard, especially when directions are sampled unevenly and at a coarse resolution. Here, we describe a Bayesian estimation procedure that improves the accuracy of curve-shape estimation even when the curve is sampled unevenly and at a very coarse resolution. Using this approach, we characterize the movement direction tuning curves in the supplementary motor area (SMA) of behaving monkeys. We compare the SMA tuning curves to tuning curves of neurons from the primary motor cortex (M1) of the same monkeys, showing that the tuning curves of the SMA neurons tend to be narrower and shallower. We also show that these characteristics do not depend on the specific location in each region.

Remembering to attend: the anterior cingulate cortex and remote memory

Damage to the hippocampus, as first demonstrated with patient HM, results in a profound anterograde and temporally-graded retrograde amnesia. The observation that older memories could still be consciously recollected led to the proposal that, over time, information initially processed in the hippocampus is stored in a distributed cortical network. The anterior cingulate cortex (ACC) has recently been implicated in this process. Studies in rodents have demonstrated that the ACC is necessary for recalling behaviors learned a month or more in the past, but not for the same behaviors learned the previous day. Precisely how the ACC contributes to the recall of remote memories is unknown. Is this role distinct from myriad others proposed for the ACC, or has the approach taken in these studies of assessing function at different points after learning provided a new window through which to view established processes? The present review seeks to address this question. First, the data will be presented implicating the ACC in recall of remote memory. This will be followed by a discussion of studies describing two other primary roles of the ACC, mediating attention and premotor planning, with an emphasis on data collected in rodents, as these will be most directly comparable to the memory studies presented. The available evidence supports a connection among these roles, and suggests a possible synthesis for otherwise seemingly disparate functions reported for the ACC.

Brain network involved in visual processing of movement stimuli used in upper limb robotic training: an fMRI study

Background

The potential of robot-mediated therapy and virtual reality in neurorehabilitation is becoming of increasing importance. However, there is limited information, using neuroimaging, on the neural networks involved in training with these technologies. This study was intended to detect the brain network involved in the visual processing of movement during robotic training. The main aim was to investigate the existence of a common cerebral network able to assimilate biological (human upper limb) and non-biological (abstract object) movements, hence testing the suitability of the visual non-biological feedback provided by the InMotion2 Robot.

Methods

A visual functional Magnetic Resonance Imaging (fMRI) task was administered to 22 healthy subjects. The task required observation and retrieval of motor gestures and of the visual feedback used in robotic training. Functional activations of both biological and non-biological movements were examined to identify areas activated in both conditions, along with differential activity in upper limb vs. abstract object trials. Control of response was also tested by administering trials with congruent and incongruent reaching movements.

Results

The observation of upper limb and abstract object movements elicited similar patterns of activations according to a caudo-rostral pathway for the visual processing of movements (including specific areas of the occipital, temporal, parietal, and frontal lobes). Similarly, overlapping activations were found for the subsequent retrieval of the observed movement. Furthermore, activations of frontal cortical areas were associated with congruent trials more than with the incongruent ones.

Conclusions

This study identified the neural pathway associated with visual processing of movement stimuli used in upper limb robot-mediated training and investigated the brain’s ability to assimilate abstract object movements with human motor gestures. In both conditions, activations were elicited in cerebral areas involved in visual perception, sensory integration, recognition of movement, re-mapping on the somatosensory and motor cortex, storage in memory, and response control. Results from the congruent vs. incongruent trials revealed greater activity for the former condition than the latter in a network including cingulate cortex, right inferior and middle frontal gyrus that are involved in the go-signal and in decision control. Results on healthy subjects would suggest the appropriateness of an abstract visual feedback provided during motor training. The task contributes to highlight the potential of fMRI in improving the understanding of visual motor processes and may also be useful in detecting brain reorganisation during training.

Neural correlates of long-term object memory in the mouse anterior cingulate cortex

Damage to the hippocampal formation results in a profound temporally graded retrograde amnesia, implying that it is necessary for memory acquisition but not its long-term storage. It is therefore thought that memories are transferred from the hippocampus to the cortex for long-term storage in a process called systems consolidation (Dudai and Morris, 2000). Where in the cortex this occurs remains an open question. Recent work (Frankland et al., 2005; Vetere et al., 2011) suggests the anterior cingulate cortex (ACC) as a likely candidate area, but there is little direct electrophysiological evidence to support this claim. Previously, we demonstrated object-associated firing correlates in caudal ACC during tests of recognition memory and described evidence of neuronal responses to where an object had been following a brief delay. However, long-term memory requires evidence of more durable representations. Here we examined the activity of ACC neurons while testing for long-term memory of an absent object. Mice explored two objects in an arena and then were returned 6 h later with one of the objects removed. Mice continued to explore where the object had been, demonstrating memory for that object. Remarkably, some ACC neurons continued to respond where the object had been, while others developed new responses in the absent object's location. The incidence of absent-object responses by ACC neurons was greatly increased with increased familiarization to the objects, and such responses were still evident 1 month later. These data strongly suggest that the ACC contains neural correlates of consolidated object/place association memory.

Ultrafast bold fMRI using single-shot spin-echo echo planar imaging

The choice of imaging parameters for functional MRI can have an impact on the accuracy of functional localization by affecting the image quality and the degree of blood oxygenation-dependent (BOLD) contrast achieved. By improving sampling efficiency, parallel acquisition techniques such as sensitivity encoding (SENSE) have been used to shorten readout trains in single-shot (SS) echo planar imaging (EPI). This has been applied to susceptibility artifact reduction and improving spatial resolution. SENSE together with single-shot spin-echo (SS-SE) imaging may also reduce off-resonance artifacts. The goal of this work was to investigate the BOLD response of a SENSE-adapted SE-EPI on a three Tesla scanner. Whole-brain fMRI studies of seven healthy right hand-dominant volunteers were carried out in a three Tesla scanner. fMRI was performed using an SS-SE EPI sequence with SENSE. The data was processed using statistical parametric mapping. Both, group and individual subject data analyses were performed. Individual average percentage and maximal percentage signal changes attributed to the BOLD effect in M1 were calculated for all the subjects as a function of echo time. Corresponding activation maps and the sizes of the activated clusters were also calculated. Our results show that susceptibility artifacts were reduced with the use of SENSE; and the acquired BOLD images were free of the typical quadrature artifacts of SS-EPI. Such measures are crucial at high field strengths. SS SE-EPI with SENSE offers further benefits in this regard and is more specific for oxygenation changes in the microvasculature bed. Functional brain activity can be investigated with the help of single-shot spin echo EPI using SENSE at high magnetic fields.

Common anatomical and external coding for hands and feet in tactile attention: evidence from event-related potentials

Recent studies have suggested that the location of tactile stimuli is automatically recoded from anatomical into external coordinates, independent of the task requirements. However, research has mainly involved the two hands, which may not be representative for the whole body because they are excessively used for the visually guided manipulation of objects and tools. We recorded event-related potentials (ERPs) while participants received tactile stimuli to the hands and feet, but attended only one limb. The hands were placed near the feet either in an uncrossed or a crossed posture, thus varying the spatial distance of each hand from each foot. Centro-parietal ERPs 100-140 msec poststimulus were more positive when stimulating the anatomically same-side hand while attending a foot. They were also more positive when the Euclidean distance between the stimulated hand and the attended foot was small rather than large. When a foot was stimulated and a hand attended, a similar modulation of foot ERPs was observed for the right foot. To assess the spatial distance between two limbs in space, the external location of both must be known. The present ERP results therefore suggest that not only the hands but also other body parts are remapped into external coordinates. The use of both anatomical and external coordinates may facilitate the control of actions toward tactile events and the choice of the most suitable effector.

Conditional selection of contra- and ipsilateral forelimb movements by the dorsal premotor cortex in monkeys

It has been suggested that the dorsal premotor cortex (PMd) may contribute to conditional motor behavior. Thus when a selection is instructed by arbitrary conditional cues, it is possible that the unilateral PMd affects behavior, regardless of which arm, contra- or ipsilateral, is to be used. We examined this possibility by recording neuronal activity and injecting muscimol into the caudal PMd (PMdc) of monkeys while they were performing a reaching task toward visuospatial targets with either the right or left arm, as instructed by low-frequency or high-frequency tone signals. Following the injection of a small amount of muscimol (1 microL; 5 microg/microL) into the unilateral PMdc, monkeys exhibited two major deficits in behavioral performance: 1) erroneous selection of the arm not indicated by the instruction (selection errors) and 2) no movement initiation in response to a visuospatial target cue serving as a trigger signal for reaching within the reaction time limit (movement initiation errors). Errors were observed following unilateral muscimol injection into both right and left PMdc, although selection errors occurred with significantly greater frequency in the arm contralateral to the injection site. By contrast, movement initiation errors were more commonly observed in left-arm trials, regardless of whether the right or left PMdc was inactivated. Notably, errors rarely occurred following a ventral PM muscimol injection. These results suggest that the left and right PMdc cooperate to transform conditional sensory cues into appropriate motor output and can affect both contra- and ipsilateral body movement.

Cingulate cortex: diverging data from humans and monkeys

Cognitive neuroscience research relies, in part, on homologies between the brains of human and non-human primates. A quandary therefore arises when presumed anatomical homologues exhibit different functional properties. Such a situation has recently arisen in the case of the anterior cingulate cortex (ACC). In humans, numerous studies suggest a role for ACC in detecting conflicts in information processing. Studies of macaque monkey ACC, in contrast, have failed to find conflict-related responses. We consider several interpretations of this discrepancy, including differences in research methodology and cross-species differences in functional neuroanatomy. New directions for future research are outlined, emphasizing the importance of distinguishing illusory cross-species differences from the true evolutionary differences that make our species unique.

Cortical and subcortical correlates of functional electrical stimulation of wrist extensor and flexor muscles revealed by fMRI

The main scope of this study was to test the feasibility and reliability of FES in a MR-environment. Functional Electrical Stimulation (FES) is used in the rehabilitation therapy of patients after stroke or spinal cord injury to improve their motor abilities. Its principle lies in applying repeated electrical stimulation to the relevant nerves or muscles for eliciting either isometric or concentric contractions of the treated muscles. In this study we report cerebral activation patterns in healthy subjects undergoing fMRI during FES stimulation. We stimulated the wrist extensor and flexor muscles in an alternating pattern while BOLD-fMRI was recorded. We used both block and event-related designs to demonstrate their feasibility for recording FES activation in the same cortical and subcortical areas. Six out of fifteen subjects repeated the experiment three times within the same session to control intraindividual variance. In both block and event-related design, the analysis revealed an activation pattern comprising the contralateral primary motor cortex, primary somatosensory cortex and premotor cortex; the ipsilateral cerebellum; bilateral secondary somatosensory cortex, the supplementary motor area and anterior cingulate cortex. Within the same subjects we observed a consistent replication of the activation pattern shown in overlapping regions centered on the peak of activation. Similar time course within these regions were demonstrated in the event-related design. Thus, both techniques demonstrate reliable activation of the sensorimotor network and eventually can be used for assessing plastic changes associated with FES rehabilitation treatment.

Through the looking glass: counter-mirror activation following incompatible sensorimotor learning

The mirror system, comprising cortical areas that allow the actions of others to be represented in the observer's own motor system, is thought to be crucial for the development of social cognition in humans. Despite the importance of the human mirror system, little is known about its origins. We investigated the role of sensorimotor experience in the development of the mirror system. Functional magnetic resonance imaging was used to measure neural responses to observed hand and foot actions following one of two types of training. During training, participants in the Compatible (control) group made mirror responses to observed actions (hand responses were made to hand stimuli and foot responses to foot stimuli), whereas the Incompatible group made counter-mirror responses (hand to foot and foot to hand). Comparison of these groups revealed that, after training to respond in a counter-mirror fashion, the relative action observation properties of the mirror system were reversed; areas that showed greater responses to observation of hand actions in the Compatible group responded more strongly to observation of foot actions in the Incompatible group. These results suggest that, rather than being innate or the product of unimodal visual or motor experience, the mirror properties of the mirror system are acquired through sensorimotor learning.

Embodied semantics for actions: findings from functional brain imaging

The theory of embodied semantics for actions specifies that the sensory-motor areas used for producing an action are also used for the conceptual representation of the same action. Here we review the functional imaging literature that has explored this theory and consider both supporting as well as challenging fMRI findings. In particular we address the representation of actions and concepts as well as literal and metaphorical phrases in the premotor cortex.

Laterality of movement-related activity reflects transformation of coordinates in ventral premotor cortex and primary motor cortex of monkeys

The ventral premotor cortex (PMv) and the primary motor cortex (MI) of monkeys participate in various sensorimotor integrations, such as the transformation of coordinates from visual to motor space, because the areas contain movement-related neuronal activity reflecting either visual or motor space. In addition to relationship to visual and motor space, laterality of the activity could indicate stages in the visuomotor transformation. Thus we examined laterality and relationship to visual and motor space of movement-related neuronal activity in the PMv and MI of monkeys performing a fast-reaching task with the left or right arm, toward targets with visual and motor coordinates that had been dissociated by shift prisms. We determined laterality of each activity quantitatively and classified it into four types: activity that consistently depended on target locations in either head-centered visual coordinates (V-type) or motor coordinates (M-type) and those that had either differential or nondifferential activity for both coordinates (B- and N-types). A majority of M-type neurons in the areas had preferences for reaching movements with the arm contralateral to the hemisphere where neuronal activity was recorded. In contrast, most of the V-type neurons were recorded in the PMv and exhibited less laterality than the M-type. The B- and N-types were recorded in the PMv and MI and exhibited intermediate properties between the V- and M-types when laterality and correlations to visual and motor space of them were jointly examined. These results suggest that the cortical motor areas contribute to the transformation of coordinates to generate final motor commands.

Electrophysiological and hemodynamic evidence for late maturation of hand power grip and force control under visual feedback

Several human imaging studies have described the neural network involved in power grip under visual control and the subset of cortical areas within this network that are sensitive to force modulation. As there is behavioral evidence for late maturation in even simple hand motor tasks involving visual feedback, we aimed at identifying the neural correlates of these developmental changes. Subjects from three developmental age groups (9-11, 15-17, and adults) performed the same power grip task in both a functional magnetic resonance imaging and an event-related potential (ERP) session. Trials started with a visual target indicating whether to squeeze at 20%, 40%, or 75% of their maximum and online visual feedback on the actual amount of force was provided. Longer reaction times and more shallow slopes of the force curve characterized the behavior of the younger age groups, especially the children. Both neurophysiological methods detected both general as well as force modulation-specific maturational changes. General development was characterized by decreasing ERP amplitudes and increasing deactivation of an extended network, closely resembling the so-called "default" network. The most pronounced developmental changes specific for force control were observed in an ERP component and brain regions involved in feedback processing. In contrast to adult subjects, we found evidence for a stronger dependency on visual feedback information in the younger age groups. Our results also suggest that the ability to deactivate task-irrelevant networks might be a late developmental achievement.

Global activation of primary motor cortex during voluntary movements in man

Unilateral voluntary movements are accompanied by robust activation of contralateral primary motor cortex (M1) in a somatotopic fashion. Occasionally, coactivation of M1 (M1-CoA) ipsilateral to the movement was described. In a study with brain tumor patients, we consistently observed additional somatotopic M1-CoAs and hypothesized that they might represent a basic feature of movement execution. To test this hypothesis, we used BOLD functional magnetic resonance imaging in healthy subjects and show that unilateral voluntary movements of the fingers or toes go along not only with contralateral M1 activation, but also with ipsilateral M1-CoA of the respective homotopic representation and bilateral M1-CoA of different heterotopic representations not directly involved in the executed movement. Moreover, bilateral M1-CoA of heterotopic representations was observed in tongue movements. All M1-CoAs respected the correct somatotopy; however, their Euclidean coordinates were shifted and resembled to those obtained for imagined movements rather than for actual movements. BOLD signal intensities and correlations to the applied hemodynamic reference function were lower in M1-CoAs as compared to the M1 activations driving the movement but did not differ between homo- and heterotopic M1-CoAs. Thus, we propose that specific unilateral voluntary movements are accompanied by a global activation of primary motor areas, reflecting an overall increase in neuronal activity and unraveling the fundamental principle of distributed processing in M1. Executive motor function may rely on a balance of inhibitory and excitatory neuronal activity, where actual movement would result from a shift towards excitation.

Differential Involvement of Neurons in the Dorsal and Ventral Premotor Cortex During Processing of Visual Signals for Action Planning

We examined neuronal activity in the dorsal and ventral premotor cortex (PMd and PMv, respectively) to explore the role of each motor area in processing visual signals for action planning. We recorded neuronal activity while monkeys performed a behavioral task during which two visual instruction cues were given successively with an intervening delay. One cue instructed the location of the target to be reached, and the other indicated which arm was to be used. We found that the properties of neuronal activity in the PMd and PMv differed in many respects. After the first cue was given, PMv neuron response mostly reflected the spatial position of the visual cue. In contrast, PMd neuron response also reflected what the visual cue instructed, such as which arm to be used or which target to be reached. After the second cue was given, PMv neurons initially responded to the cue's visuospatial features and later reflected what the two visual cues instructed, progressively increasing information about the target location. In contrast, the activity of the majority of PMd neurons responded to the second cue with activity reflecting a combination of information supplied by the first and second cues. Such activity, already reflecting a forthcoming action, appeared with short latencies (<400 ms) and persisted throughout the delay period. In addition, both the PMv and PMd showed bilateral representation on visuospatial information and motor-target or effector information. These results further elucidate the functional specialization of the PMd and PMv during the processing of visual information for action planning.

Functional neuroimaging studies of cognitive recovery after acquired brain damage in adults

The first two decades of cognitive neuroimaging research have provided a constant increase of the knowledge about the neural organization of cognitive processes. Many cognitive functions (e.g.working memory) can now be associated with particular neural structures, and ongoing research promises to clarify this picture further, providing a new mapping between cognitive and neural function. The main goal of this paper is to outline conceptual issues that are particularly important in the context of imaging changes in neural function through recovery process. This review focuses primarily on studies made in stroke and traumatic brain injury patients, but most of the issues raised here are also relevant to studies using other acquired brain damages. Finally, we summarize a set of methodological issues related to functional neuroimaging that are relevant for the study of neural plasticity and recovery after rehabilitation.

Neural circuits involved in imitation and perspective-taking

Is it important to adopt the perspective of the model when learning a new skill? Is the "mirror system" equally involved when the teacher is facing or side-by-side with students? In this functional MRI study, we measured the cerebral hemodynamic changes in participants who watched video-clips depicting simple hand or foot actions. The participants either watched passively or imitated these actions. Half the video-clips depicted actions filmed from the perspective of the participant (1st-person perspective) and half from a frontal view as if watching someone else (3rd-person perspective). Behavioral results showed that latency to imitate was significantly shorter for the 1st-person perspective than the 3rd-person perspective. Functional imaging results demonstrate that the observation of intransitive actions engaged primary visual and extrastriate visual areas, but not the premotor cortex. Imitation vs. observation of actions yielded enhanced signal in the contralateral somatosensory and motor cortices, cerebellum, left inferior parietal lobule and superior parietal cortex, and left ventral premotor cortex. Activity in the lateral occipital cortex around the extrastriate body area was significantly enhanced during imitation, as compared to observation of actions confirming that this region involvement reaches beyond the perception of body parts. Moreover, comparisons of the two visual perspectives showed more activity in the left sensory-motor cortex for 1st-person, even during observation alone, and in the lingual gyrus for 3rd-person perspective. These findings suggest that the 1st-person perspective is more tightly coupled to the sensory-motor system than the 3rd-person perspective, which requires additional visuospatial transformation.

Subcortical motor plasticity in patients with sporadic ALS: An fMRI study

OBJECTIVE

To address the potential contribution of subcortical brain regions in the functional reorganization of the motor system in patients with sporadic ALS (sALS) and to investigate whether functional changes in brain activity are different in sALS patients with predominant upper motor neuron (UMN) or lower motor neuron (LMN) dysfunction.

METHODS

We studied 16 patients with sALS and 13 healthy controls, using BOLD-fMRI, while they performed a simple visually paced motor task. Seven patients had definite clinical UMN signs while nine patients had prevalent clinical and electrophysiological LMN involvement. fMRI data were analyzed with Brain Voyager QX.

RESULTS

Task-related functional changes were identified in motor cortical regions in both patients and healthy controls. Direct group comparisons revealed relatively decreased BOLD fMRI responses in left sensorimotor cortex, lateral premotor area, supplementary motor area and right posterior parietal cortex (p < 0.05 corrected) and relatively increased responses in the left anterior putamen (p < 0.001 uncorrected) in sALS patients. Additional analyses between the two patients subgroups demonstrated significant BOLD fMRI response differences in the anterior cingulate cortex and right caudate nucleus (p < 0.001 uncorrected) with more robust activation of these areas in patients with greater UMN burden. Importantly, there were no significant differences in performance of the motor task between sALS patients and controls as well as between sALS patient subgroups.

CONCLUSIONS

Our data demonstrate a different BOLD fMRI pattern between our sALS patients and healthy controls even during simple motor behavior. Furthermore, patients with sALS and greater UMN involvement show a different reorganization of the motor system compared to sALS patients with greater LMN dysfunction.

Complex Motor Function in Humans: Validating and Extending the Postulates of Alexandr R. Luria

OBJECTIVE

We used functional brain imaging to reevaluate Luria's postulates and to elaborate the neural circuitry underlying performance of complex motor tasks.

BACKGROUND

The anatomic organization and physiologic functioning of the normal human motor system have great significance for understanding motor dysfunction and remediation in neurology. Working with victims of penetrating head injuries, noted Russian neuropsychologist Aleksandr R. Luria designed several tests of fine motor control to understand their difficulties with complex voluntary movements. This led to his postulates that such function involves the premotor cortices and their interaction with the parietal lobe.

METHOD

Six healthy young adults performed the hand imitation, fist-scissors-gun, and piano key tasks during blood oxygen level-dependent functional magnetic resonance imaging at 3 T.

RESULTS

All 3 tasks revealed activation of both premotor and parietal cortices. Furthermore, while hand Imitation relied more on the ventral premotor area and right parietal lobe, fist-scissors-gun and piano key relied more on the supplementary motor cortex.

CONCLUSIONS

We postulate that differences in task-dependent activations across these tasks relate to degrees of sequential movement, pacing, and imitation. These results uphold Luria's original hypotheses, and extend that work by providing a further characterization of the motor areas involved in complex motor behaviors.

Effects of long-term practice and task complexity in musicians and nonmusicians performing simple and complex motor tasks: implications for cortical motor organization

Motor practice induces plastic changes within the cortical motor system. Whereas rapidly evolving changes of cortical motor representations were the subject of a number of recent studies, effects of long-term practice on the motor system are so far poorly understood. In the present study pianists and nonmusicians were investigated using functional magnetic resonance imaging. Both groups performed simple and complex movement sequences on a keyboard with the right hand, the tasks requiring different levels of ordinal complexity. The aim of this study was to characterize motor representations related to sequence complexity and to long-term motor practice. In nonmusicians, complex motor sequences showed higher fMRI activations of the presupplementary motor area (pre-SMA) and the rostral part of the dorsal premotor cortex (PMd) compared to simple motor sequences, whereas musicians showed no differential activations. These results may reflect the higher level of visuomotor integration required in the complex task in nonmusicians, whereas in musicians this rostral premotor network was employed during both tasks. Comparison of subject groups revealed increased activation of a more caudal premotor network in nonmusicians comprising the caudal part of the PMd and the supplementary motor area. This supports recent results suggesting a specialization within PMd. Furthermore, we conclude that plasticity due to long-term practice mainly occurs in caudal motor areas directly related to motor execution. The slowly evolving changes in M1 during motor skill learning may extend to adjacent areas, leading to more effective motor representations in pianists.

Responses of human anterior cingulate cortex microdomains to error detection, conflict monitoring, stimulus-response mapping, familiarity, and orienting

Human anterior cingulate cortex (ACC) activity modulation has been observed in numerous tasks, consistent with a wide variety of functions. However, previous recordings have not had sufficient spatial resolution to determine whether microdomains (approximately one to two columns) are involved in multiple tasks, how activity is distributed across cortical layers, or indeed whether modulation reflected neuronal excitation, inhibition, or both. In this study, linear arrays of 24 microelectrodes were used to estimate population synaptic currents and neuronal firing in different layers of ACC during simple/choice reaction time, delayed word recognition, rhyming, auditory oddball, and cued conditional letter-discrimination tasks. Responses to all tasks, with differential responses to errors, familiarity, difficulty, and orienting, were recorded in single microdomains. The strongest responses occurred approximately 300-800 ms after stimulus onset and were usually a current source with inhibited firing, strongly suggesting active inhibition in superficial layers during the behavioral response period. This was usually followed by a sink from approximately 800 to 1400 ms, consistent with postresponse rebound activation. Transient phase locking of task-related theta activity in superficial cingulate layers suggested extended interactions with medial and lateral frontal and temporal sites. These data suggest that each anterior cingulate microdomain participates in a multilobar cortical network after behavioral responses in a variety of tasks.

Ankle dorsiflexion as an fMRI paradigm to assay motor control for walking during rehabilitation

The ability to walk independently with the velocity and endurance that permit home and community activities is a highly regarded goal for neurological rehabilitation after stroke. This pilot study explored a functional magnetic resonance imaging (fMRI) activation paradigm for its ability to reflect phases of motor learning over the course of locomotor rehabilitation-mediated functional gains. Ankle dorsiflexion is an important kinematic aspect of the swing and initial stance phase of the gait cycle. The motor control of dorsiflexion depends in part on descending input from primary motor cortex. Thus, an fMRI activation paradigm using voluntary ankle dorsiflexion has face validity for the serial study of walking-related interventions. Healthy control subjects consistently engaged contralateral primary sensorimotor cortex (S1M1), supplementary motor area (SMA), premotor (PM) and cingulate motor (CMA) cortices, and ipsilateral cerebellum. Four adults with chronic hemiparetic stroke evolved practice-induced representational plasticity associated with gains in speed, endurance, motor control, and kinematics for walking. For example, an initial increase in activation within the thoracolumbar muscle representation of S1M1 in these subjects was followed by more focused activity toward the foot representation with additional pulses of training. Contralateral CMA and the secondary sensory area also reflected change with practice and gains. We demonstrate that the supraspinal sensorimotor network for the neural control of walking can be assessed indirectly by ankle dorsiflexion. The ankle paradigm may serve as an ongoing physiological assay of the optimal type, duration, and intensity of rehabilitative gait training.

What Disconnection Tells about Motor Imagery: Evidence from Paraplegic Patients

Brain activation during motor imagery has been the subject of a large number of studies in healthy subjects, leading to divergent interpretations with respect to the role of descending pathways and kinesthetic feedback on the mental rehearsal of movements. We investigated patients with complete spinal cord injury (SCI) to find out how the complete disruption of motor efferents and sensory afferents influences brain activation during motor imagery of the disconnected feet. Eight SCI patients underwent behavioral assessment and functional magnetic resonance imaging. When compared to a healthy population, stronger activity was detected in primary and all non-primary motor cortical areas and subcortical regions. In paraplegic patients the primary motor cortex was consistently activated, even to the same degree as during movement execution in the controls. Motor imagery in SCI patients activated in parallel both the motor execution and motor imagery networks of healthy subjects. In paraplegics the extent of activation in the primary motor cortex and in mesial non-primary motor areas was significantly correlated with the vividness of movement imagery, as assessed by an interview. The present findings provide new insights on the neuroanatomy of motor imagery and the possible role of kinesthetic feedback in the suppression of cortical motor output required during covert movements.

Activations related to "mirror" and "canonical" neurones in the human brain: an fMRI study

In the macaque monkey ventral premotor cortex (F5), "canonical neurones" are active when the monkey observes an object and when the monkey grasps that object. In the same area, "mirror neurones" fire both when the monkey observes another monkey grasping an object and when the monkey grasps that object. We used event-related fMRI to investigate where in the human brain activation can be found that reflects both canonical and mirror neuronal activity. There was activation in the intraparietal and ventral limbs of the precentral sulcus when subjects observed objects and when they executed movements in response to the objects (canonical neurones). There was activation in the dorsal premotor cortex, the intraparietal cortex, the parietal operculum (SII), and the superior temporal sulcus when subjects observed gestures (mirror neurones). Finally, activations in the ventral premotor cortex and inferior frontal gyrus (area 44) were found when subjects imitated gestures and executed movements in response to objects. We suggest that in the human brain, the ventral limb of the precentral sulcus may form part of the area designated F5 in the macaque monkey. It is possible that area 44 forms an anterior part of F5, though anatomical studies suggest that it may be a transitional area between the premotor and prefrontal cortices.

Somatomotor functional MRI in a large congenital arachnoid cyst

The immature human brain, when damaged, is able to reorganise functionally. We performed functional MRI during eight different movements in a patient found incidentally to have an extensive, frontal, congenital arachnoid cyst, looking at which neural substrates contribute to motor control. Significant changes from the normal pattern of activation were seen in cortical and cerebellar areas which could not be accounted for by the space-occupying effect of the cyst alone. These findings in this asymptomatic patient with a congenital anomaly demonstrate an alternative organisation of the central motor system, with a preservation of neurological function.

Neural activity in primary motor and dorsal premotor cortex in reaching tasks with the contralateral versus ipsilateral arm

To investigate the effector dependence of task-related neural activity in dorsal premotor (PMd) and primary motor cortex (M1), directional tuning functions were compared between instructed-delay reaching tasks performed separately with either the contralateral or the ipsilateral limb. During presentation of the instructional cue, the majority (55/90, 61%) of cells in PMd were tuned with both arms, and their dynamic range showed a trend for stronger discharge with the contralateral arm. Most strikingly, however, the preferred direction of most of these latter cells (41/55, 75%) was not significantly different between arms. During movement, many PMd cells continued to be tuned with both arms (53/90, 59%), with a trend for increasing directional differences between the arms over the course of the trial. In contrast, during presentation of the instructional cue only 5/74 (7%) cells in M1 were tuned with both arms. During movement, about half of M1 cells (41/74, 55%) were tuned with both arms but the preferred directions of their tuning functions were often very different and there was a strong bias toward greater discharge rates when the contralateral arm was used. Similar trends were observed for EMG activity. In conclusion, M1 is strongly activated during movements of the contralateral arm, but activity during ipsilateral arm movements is also common and usually different from that seen with the contralateral arm. In contrast, a major component of task-related activity in PMd represents movement in a more abstract or task-dependent and effector-independent manner, especially during the instructed-delay period.

Somatotopy in the ipsilateral primary motor cortex

Conflicting reports exist about the occurrence, reliability and localization of activation in the ipsilateral primary motor cortex (M1). We re-examined this issue with functional magnetic resonance imaging in 12 volunteers performing right hand, finger, wrist, elbow, foot and tongue movements in two separate sessions. Ipsilateral M1 activation was inconsistently and non-reliably present during all movements: in 54% of all hand, 50% elbow, 46% finger, 33% wrist, and in 17% of all foot experiments. When compared to contralateral M1, the volumes and maximum t-values were always smaller. The ipsilateral M1 body representation was somatotopically organized with coordinates similar to the contralateral M1. Finally, the presence of ipsilateral M1 activation depended on the global activation level in other motor-related areas, which was significantly increased, when ipsilateral M1 activation was detected.