Cortico-cortical networks in patients with ideomotor apraxia as revealed by EEG coherence analysis

Altered cortical network dynamics during observing and preparing action in patients with corticobasal syndrome

Corticobasal syndrome (CBS) is characterized not only by parkinsonism but also by higher-order cortical dysfunctions, such as apraxia. However, the electrophysiological mechanisms underlying these symptoms remain poorly understood. To explore the pathophysiology of CBS, we recorded magnetoencephalographic (MEG) data from 17 CBS patients and 20 age-matched controls during an observe-to-imitate task. This task involved observing a tool-use video (action observation), withholding movement upon a Go cue (movement preparation), and subsequently imitating the tool-use action. We analyzed spectral power modulations at the source level. During action observation, event-related beta power (13-30 Hz) suppression was weaker in CBS patients compared to controls. This reduction was evident bilaterally in superior parietal, primary motor, premotor and inferior frontal cortex. During movement preparation, beta power suppression was also reduced in CBS patients, correlating with longer reaction times. Immediately prior to movement onset, however, beta suppression was comparable between groups. Our findings suggest that action observation induces beta suppression, likely indicative of motor cortical disinhibition, which is impaired in CBS patients. This alteration may represent a neural correlate of disrupted visuo-motor mapping in CBS. The altered timing of beta suppression to the Go cue suggests deficits in learning the task's temporal structure rather than in movement initiation itself.

Effect of tDCS on corticomuscular coupling and the brain functional network of stroke patients

Transcranial direct current stimulation (tDCS) is an emerging brain intervention technique that has gained growing attention in recent years in the rehabilitation area. In this paper, we investigated the efficacy of tDCS in the rehabilitation process of stroke patients, utilizing corticomuscular coupling (CMC) and brain functional network analysis. Specifically, we examined changes in CMC relationships between the treatment and control groups before and after rehabilitation by transfer entropy (TE), and constructed brain functional networks by TE. We further calculated features of the functional networks, including node degree, global efficiency, clustering coefficient, characteristic path length, and small world index. Our results demonstrate that CMC in patients increased significantly after treatment, with greater improvements in the tDCS group, particularly within the beta and gamma bands. In addition, the functional brain network analysis revealed enhanced connectivity between brain regions, improved information processing capacity, and increased transmission efficiency in patients as their condition improved. Notably, treatment with tDCS resulted in more significant improvements than the sham group, with a statistically significant difference observed after rehabilitation treatment (p < 0.05). These findings provide compelling evidence regarding the role of tDCS in the treatment of stroke and highlight the potential of this approach in stroke rehabilitation. The use of tDCS for therapeutic interventions in stroke rehabilitation can significantly improve the coupling of patients' functional brain networks. Also, using Transfer Entropy (TE) as a characteristic of CMC, tDCS was found to significantly enhance patients' TE, i.e. enhanced CMC.

Limb Apraxias: The Influence of Higher Order Perceptual and Semantic Deficits in Motor Recovery After Stroke

Stroke is a leading cause of disability worldwide. Limb apraxia is a group of higher order motor disorders associated with greater disability and dependence after stroke. Original neuropsychology studies distinguished separate brain pathways involved in perception and action, known as the dual stream hypothesis. This framework has allowed a better understanding of the deficits identified in Limb Apraxia. In this review, we propose a hierarchical organization of this disorder, in which a distinction can be made between several visuomotor pathways that lead to purposeful actions. Based on this, executive apraxias (such as limb kinetic apraxia) cause deficits in executing fine motor hand skills, and intermediate apraxias (such as optic ataxia and tactile apraxia) cause deficits in reaching to grasp and manipulating objects in space. These disorders usually affect the contralesional limb. A further set of disorders collectively known as limb apraxias include deficits in gesture imitation, pantomime, gesture recognition, and object use. These deficits are due to deficits in integrating perceptual and semantic information to generate complex movements. Limb apraxias are usually caused by left-hemisphere lesions in right-handed stroke patients, affecting both limbs. The anterior- to posterior-axis of brain areas are disrupted depending on the increasing involvement of perceptual and semantic processes with each condition. Lower-level executive apraxias are linked to lesions in the frontal lobe and the basal ganglia, while intermediate apraxias are linked to lesions in dorso-dorsal subdivisions of the dorsal fronto-parietal networks. Limb apraxias can be caused by lesions in both dorsal and ventral subdivisions including the ventro-dorsal stream and a third visuomotor pathway, involved in body schema and social cognition. Rehabilitation of these disorders with behavioral therapies has aimed to either restore perceptuo-semantic deficits or compensate to overcome these deficits. Further studies are required to better stratify patients, using modern neurophysiology and neuroimaging techniques, to provide targeted and personalized therapies for these disorders in the future.

The challenge of apraxia: Toward an operational definition?

The diagnosis of limb apraxia relies mainly on exclusion criteria (e.g., elementary motor or sensory deficits, aphasia). Due to the diversity of apraxia definitions and assessment methods, patients may or may not show apraxia depending on the chosen assessment method or theory, making the definition of apraxia somewhat arbitrary. As a result, "apraxia" may be diagnosed in patients with different cognitive impairments. Based on a quantitative and critical review of the literature, it is argued that this situation has its roots in the evolution from a task-based approach (i.e., the use of gold standard tests to detect apraxia) toward a process-based approach, namely, the deconstruction of the conceptual or production systems of action into multiple cognitive processes: language, executive functions, working memory, semantic memory, body schema, body image, visual-spatial skills, social cognition, visual-kinesthetic engrams, manipulation knowledge, technical reasoning, structural inference, and categorical apprehension. The coexistence of both approaches in the current literature is a major challenge that stands in the way of a scientific definition of apraxia. As a step toward a solution, we suggest to focus on symptoms, and on two complementary definition criteria (in addition with traditional exclusion criteria): Specificity (i.e., is apraxia explained by the alteration of cognitive processes specifically dedicated to gesture production?), and consistency (i.e., is the gesture production impairment consistent across tasks?). Two categories of limb apraxia are proposed: symptomatic apraxia (i.e., gesture production deficits that are secondary to more general cognitive impairments) and idiopathic apraxia (i.e., gesture production deficits that can be observed in isolation). It turns out that the only apraxia subtype that fulfills exclusion, specificity, and consistency criteria is limb-kinetic apraxia. A century after Liepmann's demonstration of the autonomy of apraxia toward language, the autonomy of this syndrome toward the rest of cognition remains an open question, while it poses new challenges to apraxia studies.

Post-stroke object affordances: An EEG investigation

Rehabilitating upper limb function after stroke is a key therapeutic goal. In healthy brains, objects, especially tools, are said to cause automatic motoric 'affordances'; affecting our preparation to handle objects. For example, the N2 event-related potential has been shown to correlate with the functional properties of objects in healthy adults during passive viewing. We posited that such an affordance effect might also be observed in chronic-stage stroke survivors. With either dominant or non-dominant hand forward, we presented three kinds of stimuli in stereoscopic depth; grasp objects affording a power-grip, pinch objects affording a thumb and forefinger precision-grip and an empty desk, affording no action. EEG data from 10 stroke survivors and 15 neurologically healthy subjects were analysed for the N1 and N2 ERP components. Both components revealed differences between the two object stimuli categories and the empty desk for both groups, suggesting the presence of affordance-related motor priming from around 100 to 370 ms after stimulus onset. Hence, we speculate that stroke survivors with loss of upper limb function may benefit from object presentation regimes designed to maximise motor priming when attempting movements with manipulable objects. However, further investigation would be necessary with acute stage patients, especially those diagnosed with apraxia.

Cross-frequency and iso-frequency estimation of functional corticomuscular coupling after stroke

Functional corticomuscular coupling (FCMC) between the brain and muscles has been used for motor function assessment after stroke. Two types, iso-frequency coupling (IFC) and cross-frequency coupling (CFC), are existed in sensory-motor system for healthy people. However, in stroke, only a few studies focused on IFC between electroencephalogram (EEG) and electromyogram (EMG) signals, and no CFC studies have been found. Considering the intrinsic complexity and rhythmicity of the biological system, we first used the wavelet package transformation (WPT) to decompose the EEG and EMG signals into several subsignals with different frequency bands, and then applied transfer entropy (TE) to analyze the IFC and CFC relationship between each pair-wise subsignal. In this study, eight stroke patients and eight healthy people were enrolled. Results showed that both IFC and CFC still existed in stroke patients (EEG → EMG: 1:1, 3:2, 2:1; EMG → EEG: 1:1, 2:1, 2:3, 3:1). Compared with the stroke-unaffected side and healthy controls, the stroke-affected side yielded lower alpha, beta and gamma synchronization (IFC: beta; CFC: alpha, beta and gamma). Further analysis indicated that stroke patients yielded no significant difference of the FCMC between EEG → EMG and EMG → EEG directions. Our study indicated that alpha and beta bands were essential to concentrating and maintaining the motor capacities, and provided a new insight in understanding the propagation and function in the sensory-motor system.

Exploring Cortex Connectivity Signal in Sensory Response to Odors

Recent neuroscience studies using fMRI have shown specific cortex activities are associated with scent stimuli. This has shed light on the use of EEG for investigating the neuronal processes and effects of olfactory sensory. While there were a few EEG studies using ERP or spectral power analysis, the results are often not converging or lack of generality. This study attempts to explore a potentially more generalized approach by looking into the connectivity patterns in the brain during olfactory sensing. Human olfactory system collects odorants and transduces them into neural signals which are transmitted to the olfactory bulb that connects to the orbitofrontal cortex for further processing. We study connectivity of cortex signal through the coherence analysis on scalp EEG data. We propose a novel protocol for robust olfactory stimulus identification and synchronization experiment. We adopt Magnitude Squared Coherence Estimation for coherence analysis and derived a coherence index (CI) to infer the collaborative effect derived from a region of interest, e.g., left side and right side of scalp. From the 14 subjects' EEG data, we observe the lateralization effect of olfactory processes in the human brain. The results suggest a stronger collaborative effect in the left hemisphere compare to the right side when pleasant stimuli are delivered.

The Role of Attention and Saccades on Parietofrontal Encoding of Contextual and Grasp-specific Affordances of Tools: An ERP Study

The ability to recognize a tool's affordances (how a spoon should be appropriately grasped and used), is vital for daily life. Prior research has identified parietofrontal circuits, including mirror neurons, to be critical in understanding affordances. However, parietofrontal action-encoding regions receive extensive visual input and are adjacent to parietofrontal attention control networks. It is unclear how eye movements and attention modulate parietofrontal encoding of affordances. To address this issue, scenes depicting tools in different use-contexts and grasp-postures were presented to healthy subjects across two experiments, with stimuli durations of 100 ms or 500 ms. The 100-ms experiment automatically restricted saccades and required covert attention, while the 500-ms experiment allowed overt attention. The two experiments elicited similar behavioral decisions on tool-use correctness and isolated the influence of attention on parietofrontal activity. Parietofrontal ERPs (P600) distinguishing tool-use contexts (e.g., spoon-yogurt vs. spoon-ball) were similar in both experiments. Conversely, parietofrontal ERPs distinguishing tool-grasps were characterized by posterior to frontal N130-N200 ERPs in the 100-ms experiment and by saccade-perturbed N130-N200 ERPs, frontal N400 and parietal P500 in the 500-ms experiment. Particularly, only overt gaze toward the hand-tool interaction engaged mirror neurons (frontal N400) when discerning grasps that manipulate but not functionally use a tool - (grasp bowl rather than stem of spoon). Results here detail the first human electrophysiological evidence on how attention selectively modulates multiple parietofrontal grasp-perception circuits, especially the mirror neuron system, while unaffecting parietofrontal encoding of tool-use contexts. These results are pertinent to neurophysiological models of affordances that typically neglect the role of attention in action perception.

Early dysfunctions of fronto-parietal praxis networks in Parkinson's disease

In Parkinson’s disease (PD) the prevalence of apraxia increases with disease severity implying that patients in early stages may already have subclinical deficits. The aim of this exploratory fMRI study was to investigate if subclinical aberrations of the praxis network are already present in patients with early PD. In previous functional imaging literature only data on basal motor functions in PD exists. Thirteen patients with mild parkinsonian symptoms and without clinically diagnosed apraxia and 14 healthy controls entered this study. During fMRI participants performed a pantomime task in which they imitated the use of visually presented objects. Patients were measured ON and OFF dopaminergic therapy to evaluate a potential medication effect on praxis abilities and related brain functions. Although none of the patients was apraxic according to De Renzi ideomotor scores (range 62–72), patients OFF showed significantly lower praxis scores than controls. Patients exhibited significant hyperactivation in left fronto-parietal core areas of the praxis network. Frontal activations were clearly dominant in patients and were correlated with lower individual praxis scores. We conclude that early PD patients already show characteristic signs of praxis network dysfunctions and rely on specific hyperactivations to avoid clinically evident apraxic symptoms. Subclinical apraxic deficits were shown to correlate with an activation shift from left parietal to left frontal areas implying a prospective individual imaging marker for incipient apraxia.

Altered task-related modulation of long-range connectivity in children with autism

Functional connectivity differences between children with autism spectrum disorder (ASD) and typically developing children have been described in multiple datasets. However, few studies examine the task-related changes in connectivity in disorder-relevant behavioral paradigms. In this paper, we examined the task-related changes in functional connectivity using EEG and a movement-based paradigm that has behavioral relevance to ASD. Resting-state studies motivated our hypothesis that children with ASD would show a decreased magnitude of functional connectivity during the performance of a motor-control task. Contrary to our initial hypothesis, however, we observed that task-related modulation of functional connectivity in children with ASD was in the direction opposite to that of TDs. The task-related connectivity changes were correlated with clinical symptom scores. Our results suggest that children with ASD may have differences in cortical segregation/integration during the performance of a task, and that part of the differences in connectivity modulation may serve as a compensatory mechanism. Autism Res 2018, 11: 245-257. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

LAY SUMMARY

Decreased connectivity between brain regions is thought to cause the symptoms of autism. Because most of our knowledge comes from data in which children are at rest, we do not know how connectivity changes directly lead to autistic behaviors, such as impaired gestures. When typically developing children produced complex movements, connectivity decreased between brain regions. In children with autism, connectivity increased. It may be that behavior-related changes in brain connectivity are more important than absolute differences in connectivity in autism.

Evaluating interhemispheric cortical responses to transcranial magnetic stimulation in chronic stroke: A TMS-EEG investigation

TMS-evoked cortical responses can be measured using simultaneous electroencephalography (TMS-EEG) to directly quantify cortical connectivity in the human brain. The purpose of this study was to evaluate interhemispheric cortical connectivity between the primary motor cortices (M1s) in participants with chronic stroke and controls using TMS-EEG. Ten participants with chronic stroke and four controls were tested. TMS-evoked responses were recorded at rest and during a typical TMS assessment of transcallosal inhibition (TCI). EEG recordings from peri-central gyral electrodes (C3 and C4) were evaluated using imaginary phase coherence (IPC) analyses to quantify levels of effective interhemispheric connectivity. Significantly increased TMS-evoked beta (15-30Hz frequency range) IPC was observed in the stroke group during ipsilesional M1 stimulation compared to controls during TCI assessment but not at rest. TMS-evoked beta IPC values were associated with TMS measures of transcallosal inhibition across groups. These results suggest TMS-evoked EEG responses can index abnormal effective interhemispheric connectivity in chronic stroke.

Motor imagery BCI for upper limb stroke rehabilitation: An evaluation of the EEG recordings using coherence analysis

Brain-computer interface (BCI) technology has the potential as a post-stroke rehabilitation tool, and the efficacy of the technology is most often demonstrated through output peripherals such as robots, orthosis and computers. In this study, the EEG signals recorded during the course of upper limb stroke rehabilitaion using motor imagery BCI were analyzed to better understand the effect of BCI therapy for post-stroke rehabilitation. The stroke patients recruited underwent 10 sessions of 1-hour BCI with robotic feedback for 2 weeks, 5 times a week. The analysis was performed by computing the coherences of the EEG in the lesion and contralesion side of the hemisphere from each session, and the coherence index of the lesion hemisphere (0 ≤ CI ≤ 1) was computed. The coherence index represents the rate of activation of the lesion hemisphere, and the correlation with the Fugl-Meyer assessment (FMA) before and after the BCI therapy was investigated. Significant improvement in the FMA scores was reported for five of the six patients (p = 0.01). The analysis showed that the number of sessions with CI ≥ 0.5 correlated with the change in the FMA scores. This suggests that post-stroke motor recovery best results from the activation in the lesion hemisphere, which is in agreement with previous studies performed using multimodal imaging technologies.

Opportunities for concurrent transcranial magnetic stimulation and electroencephalography to characterize cortical activity in stroke

Stroke is the leading cause of disability in the United States. Despite the high incidence and mortality of stroke, sensitive and specific brain-based biomarkers predicting persisting disabilities are lacking. Both neuroimaging techniques like electroencephalography (EEG) and non-invasive brain stimulation (NIBS) techniques such as transcranial magnetic stimulation (TMS) have proven useful in predicting prognosis, recovery trajectories and response to rehabilitation in individuals with stroke. We propose, however, that additional synergetic effects can be achieved by simultaneously combining both approaches. Combined TMS-EEG is able to activate discrete cortical regions and directly assess local cortical reactivity and effective connectivity within the network independent of the integrity of descending fiber pathways and also outside the motor system. Studying cortical reactivity and connectivity in patients with stroke TMS-EEG may identify salient neural mechanisms underlying motor disabilities and lead to novel biomarkers of stroke pathophysiology which can then be used to assess, monitor, and refine rehabilitation approaches for individuals with significant disability to improve outcomes and quality of life after stroke.

Dynamics of functional and effective connectivity within human cortical motor control networks

OBJECTIVE

Praxis, the performance of complex motor gestures, is crucial to the development of motor and social/communicative capacities. Praxis relies on a network consisting of inferior parietal and premotor regions, particularly on the left, and is thought to require transformation of spatio-temporal representations (parietal) into movement sequences (premotor).

METHOD

We examined praxis network dynamics by measuring EEG effective connectivity while healthy subjects performed a praxis task.

RESULTS

Propagation from parietal to frontal regions was not statistically greater on the left than the right. However, propagation from left parietal regions to all other regions was significantly greater during gesture preparation than execution. Moreover, during gesture preparation only, propagation from the left parietal region to bilateral frontal regions was greater than reciprocal propagations to the left parietal region. This directional specificity was not observed for the right parietal region.

CONCLUSIONS

These findings represent direct electrophysiological evidence for directionally predominant propagation in left frontal-parietal networks during praxis behavior, which may reflect neural mechanisms by which representations in the human brain select appropriate motor sequences for subsequent execution.

SIGNIFICANCE

In addition to bolstering the classic view of praxis network function, these results also demonstrate the relevance of additional information provided by directed connectivity measures.

Degradation of stored movement representations in the Parkinsonian brain and the impact of levodopa

Parkinson's disease (PD) results from the depletion of dopamine and other neurotransmitters within the basal ganglia, and is typically characterized by motor impairment (e.g., bradykinesia) and difficulty initiating voluntary movements. Difficulty initiating a movement may result from a deficit in accessing or executing a stored representation of the movement, or having to create a new representation each time a movement is required. To date, it is unclear which may be responsible for movement initiation impairments observed in PD. In this study, we used functional magnetic resonance imaging and a task in which participants passively viewed familiar and unfamiliar graspable objects, with no confounding motor task component. Our results show that the brains of PD patients implicitly analyze familiar graspable objects as if the brain has little or no motor experience with the objects. This was observed as a lack of differential activity within brain regions associated with stored movement representations for familiar objects relative to unfamiliar objects, as well as significantly greater activity for familiar objects when off levodopa relative to on medication. Symptom severity modulated this activity difference within the basal ganglia. Levodopa appears to normalize brain activity, but its effect may be one of attenuation of brain hyperactivity within the basal ganglia network, which is responsible for controlling motor behavior and the integration of visuomotor information. Overall, this study demonstrates that difficulty initiating voluntary movements experienced by PD patients may be the result of degradation in stored representations responsible for the movement.

Interactive rehabilitation and dynamical analysis of scalp EEG

Electroencephalography (EEG) has been used for decades to measure the brain's electrical activity. Planning and performing a complex movement (e.g., reaching and grasping) requires the coordination of muscles by electrical activity that can be recorded with scalp EEG from relevant regions of the cortex. Prior studies, utilizing motion capture and kinematic measures, have shown that an augmented reality feedback system for rehabilitation of stroke patients can help patients develop new motor plans and perform reaching tasks more accurately. Historically, traditional signal analysis techniques have been utilized to quantify changes in EEG when subjects perform common, simple movements. These techniques have included measures of event-related potentials in the time and frequency domains (e.g., energy and coherence measures). In this study, a more advanced, nonlinear, analysis technique, mutual information (MI), is applied to the EEG to capture the dynamics of functional connections between brain sites. In particular, the cortical activity that results from the planning and execution of novel reach trajectories by normal subjects in an augmented reality system was quantified by using statistically significant MI interactions between brain sites over time. The results show that, during the preparation for as well as the execution of a reach, the functional connectivity of the brain changes in a consistent manner over time, in terms of both the number and strength of cortical connections. A similar analysis of EEG from stroke patients may provide new insights into the functional deficiencies developed in the brain after stroke, and contribute to evaluation, and possibly the design, of novel therapeutic schemes within the framework of rehabilitation and BMI (brain machine interface).

Influence of subcortical ischemic stroke on cortical neural network

Stroke has remained as a leading cause of death and neurological disability worldwide in the past decades. Previous structural and functional studies reported little information regarding cortical neural network after stroke. Using the causality measure based on multi-channel electroencephalograph (EEG), i.e. partial directed coherence (PDC) in this paper, we investigated the different network patterns involved in pre-motor and parietal areas (F3, F4, C3, C4, P3 and P4) in three groups of patients who suffered unilateral or bilateral hemispheric stroke in basal ganglia with extension into corona radiate. Compared with the results in the control group, stroke patients showed: 1) more vulnerable long-distance intra- and inter-hemispheric interactions due to the ischemic injury; 2) strengthened short-distance interactions between the central areas in the intact hemisphere with the injured counterpart, which implied a functional compensation after unilateral stroke; 3) more suppression of cortical connections after bilateral hemispheric stroke than those with unilateral stroke. Causal interdependence by PDC analysis provides a new insight of cortical functional network following stroke.

Left parietal activation related to planning, executing and suppressing praxis hand movements

OBJECTIVE

We sought to investigate the activity of bilateral parietal and premotor areas during a Go/No Go paradigm involving praxis movements of the dominant hand.

METHODS

A sentence was presented which instructed subjects on what movement to make (S1; for example, "Show me how to use a hammer."). After an 8-s delay, "Go" or "No Go" (S2) was presented. If Go, they were instructed to make the movement described in the S1 instruction sentence as quickly as possible, and continuously until the "Rest" cue was presented 3 s later. If No Go, subjects were to simply relax until the next instruction sentence. Event-related potentials (ERP) and event-related desynchronization (ERD) in the beta band (18-22 Hz) were evaluated for three time bins: after S1, after S2, and from -2.5 to -1.5 s before the S2 period.

RESULTS

Bilateral premotor ERP was greater than bilateral parietal ERP after the S2 Go compared with the No Go. Additionally, left premotor ERP was greater than that from the right premotor area. There was predominant left parietal ERD immediately after S1 for both Go and No Go, which was sustained for the duration of the interval between S1 and S2. For both S2 stimuli, predominant left parietal ERD was again seen when compared to that from the left premotor or right parietal area. However, the left parietal ERD was greater for Go than No Go.

CONCLUSION

The results suggest a dominant role in the left parietal cortex for planning, executing, and suppressing praxis movements. The ERP and ERD show different patterns of activation and may reflect distinct neural movement-related activities.

SIGNIFICANCE

The data can guide further studies to determine the neurophysiological changes occurring in apraxia patients and help explain the unique error profiles seen in patients with left parietal damage.

Update on apraxia

Apraxia is classically defined as difficulty performing learned, skilled gestures. In this review, we describe the range of motor impairments classified as apraxia, focusing on ideomotor limb apraxia. We present several prominent models of praxis to explain the variety of difficulties seen in patients with apraxia. We also discuss the large-scale frontal-parietal-basal ganglia network thought to underlie praxis. In this context, we highlight the common occurrence of limb apraxia in corticobasal degeneration, a neurodegenerative condition characterized by frontal, parietal, and basal ganglia disease.

Gesture subtype-dependent left lateralization of praxis planning: an event-related fMRI study

Ideomotor apraxia is a disorder mainly of praxis planning, and the deficit is typically more evident in pantomiming transitive (tool related) than intransitive (communicative) gestures. The goal of the present study was to assess differential hemispheric lateralization of praxis production using event-related functional magnetic resonance imaging. Voxel-based analysis demonstrated significant activations in posterior parietal cortex (PPC) and premotor cortex (PMC) association areas, which were predominantly left hemispheric, regardless of whether planning occurred for right or left hand transitive or intransitive pantomimes. Furthermore, region of interest-based calculation of mean laterality index (LI) revealed a significantly stronger left lateralization in PPC/PMC clusters for planning intransitive (LI = -0.49 + 0.10, mean + standard deviation [SD]) than transitive gestures (-0.37 + 0.08, P = 0.02, paired t-tests) irrespective of the hand involved. This differential left lateralization for planning remained significant in PMC (LI = -0.47 + 0.14 and -0.36 + 0.13, mean + SD, P = 0.04), but not in PPC (-0.56 + 0.11 and -0.45 + 0.12, P = 0.11), when both regions were analyzed separately. In conclusion, the findings point to a left-hemispheric specialization for praxis planning, being more pronounced for intransitive gestures in PMC, possibly due to their communicative nature.