Cerebellar Activation During Simple and Complex Bimanual Coordination: an Activation Likelihood Estimation (ALE) Meta-analysis.

Bimanual coordination is an important part of everyday life and recruits a large neural network, including the cerebellum. The specific role of the cerebellum in bimanual coordination has not yet been studied in depth, although several studies indicate a differential role of the anterior and posterior cerebellum depending on the complexity of the coordination. An activation likelihood estimation (ALE) meta-analysis was used combining the data of several functional MRI studies involving bimanual coordination tasks with varying complexities to unravel the involvement of the different areas of the cerebellum in simple and complex bimanual coordination. This study confirms the general bimanual network as found by Puttemans et al. (Puttemans et al. in J Neurosci 25:4270-4278, 2005) and highlights the differences between preferred in-phase (simultaneous movements of homologous muscle groups) and anti-phase movement conditions (alternating movements of homologous muscle groups), and more complex, non-preferred bimanual movements (e.g., out-of-phase movements). Our results show a differential role for the anterior and posterior vermis in bimanual coordination, with a role for the anterior vermis in anti-phase and complex bimanual coordination, and an exclusive role for the posterior vermis in complex bimanual movements. In addition, the way complexity was manipulated also seems to play a role in the involvement of the anterior and posterior vermis. We hypothesize that the anterior vermis is involved in sequential/spatial control, while the posterior vermis is involved in temporal control of (bimanual) coordination, though other factors such as (visual) feedback and continuity of the movement also seem to have an impact. More studies are needed to unravel the specific role of the cerebellar vermis in bimanual coordination.

Cerebellum and Neurorehabilitation in Emotion with a Focus on Neuromodulation.

More and more research has focused on the role of the cerebellum in emotions and social cognition. Structural cerebellar and cerebello-cerebral connectivity abnormalities have been identified in several prevalent neuropsychiatric conditions, which have in some cases even been linked to the severity of the emotional disorder.Non-invasive brain stimulation (NIBS) techniques are currently used to modulate neuronal excitability and tune the connectivity within and between neuronal networks. Targeting the cerebellum with NIBS in order to improve emotions and social behavior in neuropsychiatric conditions seems to be a very interesting and innovative approach. Several studies have already explored the effect of cerebellar vermis stimulation in patients with schizophrenia with promising results. Other neuropsychiatric disorders such as bipolar disorder (BD), obsessive-compulsive disorder (OCD), major depressive disorder, or generalized anxiety disorder (GAD) have received less attention with respect to cerebellar stimulation, although the cerebellum has been implicated in these disorders. We will address NIBS and neuropsychiatric disorders in this chapter. Future research should focus on combining cerebellar NIBS with neuroimaging to unravel the specific role of the cerebellum in emotional disorders. Such studies will be very valuable in establishing causal relationships between the structural and functional abnormalities that can be observed in these disorders, and in the search for neurophysiological biomarkers for emotions. However, it is still unclear which stimulation parameters are optimal. Moreover, an important factor to consider when applying cerebellar NIBS in order to improve emotional or other functioning is cerebellar reserve. Although the cerebellum has a wide variety of plasticity mechanisms and its structural organization intrinsically incorporates a lot of redundancy, this redundancy can be depleted. A certain amount of cerebellar reserve should be preserved to successfully apply NIBS.Systematic studies are therefore needed to clarify the optimal stimulation parameters, and methods should be developed to quantify cerebellar reserve in order to estimate the possible added value of NIBS in the rehabilitation of emotions.

Connectivity between the cerebrum and cerebellum during social and non-social sequencing using dynamic causal modelling.

This analysis explores the effective connectivity of the cerebellum with the cerebral cortex during the generation of correct sequences of social and non-social events, using dynamic causal modelling (DCM). Our hypothesis is that during human evolution, the cerebellum's function evolved from a mere coordinator of fluent sequences of motions and actions, to an interpreter of action sequences without overt movements that are important for social understanding. This requires efficient neural communication between the cerebellum and cerebral cortex. In a functional magnetic resonance imaging (fMRI) study, participants generated the correct chronological order of (non-)social events, including stories involving mechanical and social scripts, and true or false beliefs. Across all stories, a DCM analysis of these data revealed, as predicted, bidirectional (closed-loop) connections linking the bilateral posterior cerebellum with the bilateral temporo-parietal junction (TPJ) associated with behavior understanding, and this connectivity pattern was almost entirely significant. There was also a unidirectional connection from the right posterior cerebellum to the precuneus, but no direct connections with the dorsomedial prefrontal cortex (dmPFC). Moreover, all connections emanating from the bilateral posterior cerebellum were negative, indicative of some kind of error signal. Within the cerebral cortex, there were unidirectional connections from the bilateral TPJ to the dmPFC, as well as bidirectional connections between the precuneus and dmPFC, and between the bilateral TPJ. These results confirm that the effective connectivity between the posterior cerebellum and mentalizing areas in the cerebral cortex play a critical role in the understanding and construction of the correct order of social and non-social action sequences.

The Cerebellar Cognitive Affective/Schmahmann Syndrome: a Task Force Paper.

Sporadically advocated over the last two centuries, a cerebellar role in cognition and affect has been rigorously established in the past few decades. In the clinical domain, such progress is epitomized by the "cerebellar cognitive affective syndrome" ("CCAS") or "Schmahmann syndrome." Introduced in the late 1990s, CCAS reflects a constellation of cerebellar-induced sequelae, comprising deficits in executive function, visuospatial cognition, emotion-affect, and language, over and above speech. The CCAS thus offers excellent grounds to investigate the functional topography of the cerebellum, and, ultimately, illustrate the precise mechanisms by which the cerebellum modulates cognition and affect. The primary objective of this task force paper is thus to stimulate further research in this area. After providing an up-to-date overview of the fundamental findings on cerebellar neurocognition, the paper substantiates the concept of CCAS with recent evidence from different scientific angles, promotes awareness of the CCAS as a clinical entity, and examines our current insight into the therapeutic options available. The paper finally identifies topics of divergence and outstanding questions for further research.

Consensus Paper: Cerebellum and Social Cognition.

The traditional view on the cerebellum is that it controls motor behavior. Although recent work has revealed that the cerebellum supports also nonmotor functions such as cognition and affect, only during the last 5 years it has become evident that the cerebellum also plays an important social role. This role is evident in social cognition based on interpreting goal-directed actions through the movements of individuals (social "mirroring") which is very close to its original role in motor learning, as well as in social understanding of other individuals' mental state, such as their intentions, beliefs, past behaviors, future aspirations, and personality traits (social "mentalizing"). Most of this mentalizing role is supported by the posterior cerebellum (e.g., Crus I and II). The most dominant hypothesis is that the cerebellum assists in learning and understanding social action sequences, and so facilitates social cognition by supporting optimal predictions about imminent or future social interaction and cooperation. This consensus paper brings together experts from different fields to discuss recent efforts in understanding the role of the cerebellum in social cognition, and the understanding of social behaviors and mental states by others, its effect on clinical impairments such as cerebellar ataxia and autism spectrum disorder, and how the cerebellum can become a potential target for noninvasive brain stimulation as a therapeutic intervention. We report on the most recent empirical findings and techniques for understanding and manipulating cerebellar circuits in humans. Cerebellar circuitry appears now as a key structure to elucidate social interactions.

Non-invasive Cerebellar Stimulation: Moving Towards Clinical Applications for Cerebellar and Extra-Cerebellar Disorders.

The field of non-invasive stimulation of the cerebellum is quickly expanding. The anatomical structure of the cerebellum with a high density of neurons in the superficial layer, its electrical properties, and its participation in numerous closed-loop circuits involved in motor, cognitive, and affective operations both in children and in adults make of the cerebellum a target with very high potential for neuromodulation of both cerebellar and extra-cerebellar disorders, in neurology, psychiatry, and neurosurgery. A common research effort is required to extract the optimal parameters of stimulation and to identify how non-invasive stimulation of the cerebellum modifies cerebellar plasticity and functional connectivity in remote cortical and subcortical areas. A patient stratification should be considered.

Cerebellar Cortex as a Therapeutic Target for Neurostimulation.

Non-invasive stimulation of the cerebellum is growingly applied both in the clinic and in research settings to modulate the activities of cerebello-cerebral loops. The anatomical location of the cerebellum, the high responsiveness of the cerebellar cortex to magnetic/electrical stimuli, and the implication of the cerebellum in numerous cerebello-cerebral networks make the cerebellum an ideal target for investigations and therapeutic purposes. In this mini-review, we discuss the potentials of cerebellar neuromodulation in major brain disorders in order to encourage large-scale sham-controlled research and explore this therapeutic aid further.

Oral and written picture description in individuals with aphasia.

BACKGROUND: Aphasia is characterized by difficulties in connected speech/writing. AIMS: To explore the differences between the oral and written description of a picture in individuals with chronic aphasia (IWA) and healthy controls. Descriptions were controlled for productivity, efficiency, grammatical organization, substitution behaviour and discourse organization. METHODS & PROCEDURES: Fifty IWA and 50 healthy controls matched for age, gender and education provided an oral and written description of a black-and-white situational drawing from the Dutch version of the Comprehensive Aphasia Test. Between- and within-group analyses were carried out and the reliability of the test instrument was assessed. OUTCOMES & RESULTS: The language samples of the healthy controls were more elaborate, more efficient, syntactically richer, more coherent, and consisted of fewer spoken and written language errors than the samples of the IWA. Within-group comparisons showed that connected writing is more sensitive than connected speech to capture aphasic symptoms. CONCLUSIONS & IMPLICATIONS: The analysis of both modalities (speech and writing) at the discourse level allows one to assess simultaneously micro- and macro-linguistic skills and their potential interrelations in a given IWA. Connected writing appears to be more sensitive in discriminating IWA from healthy controls than connected speech. This method for analyzing language samples should, however, be used in conjunction with other assessment tools.

Targeting the Cerebellum by Noninvasive Neurostimulation: a Review.

Transcranial magnetic and electric stimulation of the brain are novel and highly promising techniques currently employed in both research and clinical practice. Improving or rehabilitating brain functions by modulating excitability with these noninvasive tools is an exciting new area in neuroscience. Since the cerebellum is closely connected with the cerebral regions subserving motor, associative, and affective functions, the cerebello-thalamo-cortical pathways are an interesting target for these new techniques. Targeting the cerebellum represents a novel way to modulate the excitability of remote cortical regions and their functions. This review brings together the studies that have applied cerebellar stimulation, magnetic and electric, and presents an overview of the current knowledge and unsolved issues. Some recommendations for future research are implemented as well.

The Posterior Fossa and Foreign Accent Syndrome: Report of Two New Cases and Review of the Literature.

Foreign accent syndrome is a rare motor speech disorder that causes patients to speak their language with a non-native accent. In the neurogenic condition, the disorder develops after lesions in the language dominant hemisphere, often affecting Broca's area, the insula, the supplementary motor area and the primary motor cortex. Here, we present two new cases of FAS after posterior fossa lesions. The first case is a 44-year-old, right-handed, Dutch-speaking man who suffered motor speech disturbances and a left hemiplegia after a pontine infarction. Quantified SPECT showed a bilateral hypoperfusion in the inferior lateral prefrontal and medial inferior frontal regions as well as a significant left cerebellar hypoperfusion. Further clinical investigations led to an additional diagnosis of brainstem cognitive affective syndrome which closely relates to Schmahmann's syndrome. The second patient was a 72-year-old right-handed polyglot English man who suffered a stroke in the vascular territory of the left posterior inferior cerebellar artery (PICA) and developed a foreign accent in his mother tongue (English) and in a later learnt language (Dutch). In this paper, we discuss how the occurrence of this peculiar motor speech disorder can be related to a lesion affecting the posterior fossa structures.

Consensus Paper: Revisiting the Symptoms and Signs of Cerebellar Syndrome.

The cerebellum is involved in sensorimotor operations, cognitive tasks and affective processes. Here, we revisit the concept of the cerebellar syndrome in the light of recent advances in our understanding of cerebellar operations. The key symptoms and signs of cerebellar dysfunction, often grouped under the generic term of ataxia, are discussed. Vertigo, dizziness, and imbalance are associated with lesions of the vestibulo-cerebellar, vestibulo-spinal, or cerebellar ocular motor systems. The cerebellum plays a major role in the online to long-term control of eye movements (control of calibration, reduction of eye instability, maintenance of ocular alignment). Ocular instability, nystagmus, saccadic intrusions, impaired smooth pursuit, impaired vestibulo-ocular reflex (VOR), and ocular misalignment are at the core of oculomotor cerebellar deficits. As a motor speech disorder, ataxic dysarthria is highly suggestive of cerebellar pathology. Regarding motor control of limbs, hypotonia, a- or dysdiadochokinesia, dysmetria, grasping deficits and various tremor phenomenologies are observed in cerebellar disorders to varying degrees. There is clear evidence that the cerebellum participates in force perception and proprioceptive sense during active movements. Gait is staggering with a wide base, and tandem gait is very often impaired in cerebellar disorders. In terms of cognitive and affective operations, impairments are found in executive functions, visual-spatial processing, linguistic function, and affective regulation (Schmahmann's syndrome). Nonmotor linguistic deficits including disruption of articulatory and graphomotor planning, language dynamics, verbal fluency, phonological, and semantic word retrieval, expressive and receptive syntax, and various aspects of reading and writing may be impaired after cerebellar damage. The cerebellum is organized into (a) a primary sensorimotor region in the anterior lobe and adjacent part of lobule VI, (b) a second sensorimotor region in lobule VIII, and (c) cognitive and limbic regions located in the posterior lobe (lobule VI, lobule VIIA which includes crus I and crus II, and lobule VIIB). The limbic cerebellum is mainly represented in the posterior vermis. The cortico-ponto-cerebellar and cerebello-thalamo-cortical loops establish close functional connections between the cerebellum and the supratentorial motor, paralimbic and association cortices, and cerebellar symptoms are associated with a disruption of these loops.

The CAM test: a novel tool to quantify the decline in vertical upper limb pointing movements with ageing.

BACKGROUND AND AIM: Although upper limb movements in the vertical plane are very commonly used during the activities of daily life, there is still a lack of a reliable and easy standardized procedure to quantify them. In particular, ageing is associated with a decline in performances of coordinated movements, but a tool to quantify this decline is missing. METHODS: We created a novel portable test called counting arm movement test (CAM test). Participants were asked to perform fast and accurate successive pointing movements towards two fixed targets (mechanical counters) located in a vertical plane in the parasagittal axis during three different time periods (15, 30, 45 s). Each upper limb was assessed separately. The test was evaluated in a group of 63 healthy subjects (mean age ± SD 49.1 ± 19.8 years; F/M 33/30; range 18-87 years). RESULTS: Motor performances (number of clicks) significantly decreased as a function of age for both the dominant side (age effect; linear regression; p < 0.0001 for 15, 30 and 45 s) and the non-dominant side (linear regression; p < 0.0001 for 15, 30 and 45 s). Performances on the dominant and non-dominant side were linearly correlated with the time periods (p < 0.0001 on both sides). The symmetry index (ratio of performance on the dominant side divided by performance on the non-dominant side) was correlated linearly and positively with the duration of the test (y = 0.002x + 1.053; p = 0.0056). We also found a linear relationship between upper limb length and motor performance on the non-dominant side for 15 s (p = 0.023) and 45 s (p = 0.041). The test was characterized by a very high correlation between the results obtained by two investigators during two successive sessions in a subgroup of 7 subjects (Pearson product moment correlation: 0.989 for the dominant side and 0.988 for the non-dominant side). CONCLUSION: The CAM test appears as a robust and low cost tool to quantify upper limb pointing movements. In particular, the test strongly discriminates the effects of age upon motor performances in upper limbs. Future studies are now required to establish the sensitivity, specificity and reliability of this procedure in selected neuromuscular or skeletal diseases affecting the elderly.

Cerebellum and apraxia.

As early as the beginning of the nineteenth century, a variety of nonmotor cognitive and affective impairments associated with cerebellar pathology were occasionally documented. A causal link between cerebellar disease and nonmotor cognitive and affective disorders has, however, been dismissed for almost two centuries. During the past decades, the prevailing view of the cerebellum as a mere coordinator of autonomic and somatic motor function has changed fundamentally. Substantial progress has been made in elucidating the neuroanatomical connections of the cerebellum with the supratentorial association cortices that subserve nonmotor cognition and affect. Furthermore, functional neuroimaging studies and neurophysiological and neuropsychological research have shown that the cerebellum is crucially involved in modulating cognitive and affective processes. This paper presents an overview of the clinical and neuroradiological evidence supporting the view that the cerebellum plays an intrinsic part in purposeful, skilled motor actions. Despite the increasing number of studies devoted to a further refinement of the typology and anatomoclinical configurations of apraxia related to cerebellar pathology, the exact underlying pathophysiological mechanisms of cerebellar involvement remain to be elucidated. As genuine planning, organization, and execution disorders of skilled motor actions not due to motor, sensory, or general intellectual failure, the apraxias following disruption of the cerebrocerebellar network may be hypothetically considered to form part of the executive cluster of the cerebellar cognitive affective syndrome (CCAS), a highly influential concept defined by Schmahmann and Sherman (Brain 121:561-579, 1998) on the basis of four symptom clusters grouping related neurocognitive and affective deficits (executive, visuospatial, affective, and linguistic impairments). However, since only a handful of studies have explored the possible role of the cerebellum in apraxic disorders, the pathophysiological mechanisms subserving cerebellar-induced apraxia remain to be elucidated.

Apraxic agraphia following bithalamic damage.

OBJECTIVES: Apraxic agraphia (AA) is a peripheral writing disorder generally considered to result from a causative lesion in the parietal and/or prefrontal lobe of the language dominant hemisphere (De Smet, Engelborghs, Paquier, De Deyn, & Mariën, 2011). De Smet et al. (2011), however, confirmed that AA might be associated with lesions outside the typical language areas such as the cerebellum or the thalamus. We report a 32-year-old ambidextrous patient with a left frontal lobectomy who following bilateral thalamic damage developed AA. METHOD: Detailed neurolinguistic and neurocognitive test results were obtained after resection of an extensive left frontal lobe tumour by means of a set of standardised tests. Repeated investigations were performed after a bithalamic stroke. Functional imaging was performed by means of quantified SPECT. RESULTS: Normal neurolinguistic test results were obtained after tumour resection. Neurocognitive test results, however, showed a dysexecutive syndrome and frontal behavioural deficits, including response inhibition. AA occurred after a bithalamic stroke while non-handwriting written language skills, such as typing, were normal. Quantified SPECT showed a significant bifrontal hypoperfusion. CONCLUSION: Neurolinguistic follow-up findings and SPECT evidence in this unique patient with bithalamic damage for the first time indicate that AA in the alphabetic script may result from diaschisis affecting the frontal writing centre. The findings suggest that the thalamus is critically implicated in the neural network subserving graphomotor processing.

Midfrontal Theta and Cognitive Control During Interlimb Coordination Across the Adult Lifespan.

Interlimb coordination is required for adequate execution of most daily life activities. Yet, aging negatively affects interlimb coordination, impacting the quality of life in older people. Therefore, disentangling the underlying age-related neural mechanisms is of utmost importance. Here, we investigated neurophysiological processes of an interlimb reaction time task, including both simple and complex coordination modes. Midfrontal theta power, measured using electroencephalography (EEG), was analyzed as a marker for cognitive control. In total, 82 healthy adults participated, with 27 younger, 26 middle-aged, and 29 older adults. On a behavioral level, reaction time increased across the adult lifespan, and error rate was higher in older adults. Notably, aging disproportionately affected reaction times in the complex coordination modes, with larger reaction time increases from simple to complex movements than in younger adults, starting already at middle age. On the neurophysiological level, EEG showed that only younger adults had significantly increased levels of midfrontal theta power during complex relative to simple coordination modes, while no significant differences were found between simple and complex movements in middle-aged and older adults. The absence of this theta power upregulation with regard to movement complexity with increasing age might reflect a premature saturation of the available mental resources.

Optimizing the Effect of tDCS on Motor Sequence Learning in the Elderly.

One of the most visible effects of aging, even in healthy, normal aging, is a decline in motor performance. The range of strategies applicable to counteract this deterioration has increased. Transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique that can promote neuroplasticity, has recently gained attention. However, knowledge about optimized tDCS parameters in the elderly is limited. Therefore, in this study, we investigated the effect of different anodal tDCS intensities on motor sequence learning in the elderly. Over the course of four sessions, 25 healthy older adults (over 65 years old) completed the Serial Reaction Time Task (SRTT) while receiving 1, 2, or 3 mA of anodal or sham stimulation over the primary motor cortex (M1). Additionally, 24 h after stimulation, motor memory consolidation was assessed. The results confirmed that motor sequence learning in all tDCS conditions was maintained the following day. While increased anodal stimulation intensity over M1 showed longer lasting excitability enhancement in the elderly in a prior study, the combination of higher intensity stimulation with an implicit motor learning task showed no significant effect. Future research should focus on the reason behind this lack of effect and probe alternative stimulation protocols.

Age-related changes in midfrontal theta activity during steering control: A driving simulator study.

Motor control, a ubiquitous part of driving, requires increased cognitive controlled processing in older adults relative to younger adults. However, the influence of aging on motor-related neural mechanisms in the context of driving has rarely been studied. The present study aimed to identify age-related changes in cognitive control and attention allocation during a simulated steering task, using electroencephalography. Midfrontal theta, a marker for cognitive control, and posterior alpha power, a marker for attention allocation, were measured in a total of 26 young, 25 middle-aged, and 28 older adults. By adapting driving speed, the difficulty level of this steering task was individualized for each participant. Results show age-related changes in midfrontal theta power, but not in posterior alpha power, despite similar steering accuracy across age groups. Specifically, only younger and, to a lesser extent, middle-aged adults exhibited increased theta power while driving through more demanding curved segments relative to straight segments. In contrast, theta power upregulation was absent in older adults, suggesting a saturation of cognitive resources while driving, possibly due to a limitation in resource capacity, or less automatic motor-related neural processing.

Motor sequence learning in a goal-directed stepping task in persons with multiple sclerosis: a pilot study.

Motor sequence learning in persons with multiple sclerosis (pwMS) and healthy controls (HC) under implicit or explicit learning conditions has not yet been investigated in a stepping task. Given the prevalent cognitive and mobility impairments in pwMS, this is important in order to understand motor learning processes and optimize rehabilitation strategies. Nineteen pwMS (the Expanded Disability Status Scale = 3.4 ± 1.2) and 18 HC performed a modified serial reaction time task by stepping as fast as possible on a stepping tile when it lit up, either with (explicit) or without (implicit) knowledge of the presence of a sequence beforehand. Motor sequence learning was studied by examining response time changes and differences between sequence and random blocks during the learning session (acquisition), 24 h later (retention), and in three dual-task (DT) conditions at baseline and retention (automaticity) using subtracting sevens, verbal fluency, and vigilance as concurrent cognitive DTs. Response times improved and were lower for the sequenced compared with the random blocks at the post- and retention tests (P's < 0.001). Response times during DT conditions improved after learning, but DT cost improved only for the subtracting sevens DT condition. No differences in learning were observed between learning conditions or groups. This study showed motor sequence learning, by acquisition and retention, in a stepping task in pwMS with motor impairments, to a similar degree as HC and regardless of learning conditions. Whether automaticity increased remains unclear.

Age and Interlimb Coordination Complexity Modulate Oscillatory Spectral Dynamics and Large-scale Functional Connectivity.

Interlimb coordination deteriorates as a result of aging. Due to its ubiquity in daily life, a greater understanding of the underlying neurophysiological changes is required. Here, we combined electroencephalography time-frequency spectral power and functional connectivity analyses to provide a comprehensive overview of the neural dynamics underlying the age-related deterioration of interlimb coordination involving all four limbs. Theta, alpha and beta oscillations in the frontal, central and parietal regions were analyzed in twenty younger (18-30 years) and nineteen older adults (65-78 years) during a complex interlimb reaction time task. Reaction time was significantly higher in older adults across all conditions, and the discrepancy between both age groups was largest in the most complex movement condition. Older adults demonstrated enhanced beta event-related desynchronization (i.e., the attenuation of beta power), which further increased along with task complexity and was positively linked to behavioral performance. Theta functional connectivity between frontal, central and parietal regions generally increased with movement complexity, irrespective of age group. In general, frontoparietal alpha band functional connectivity tended to be reduced in older versus younger adults, although these contrasts did not survive multiple comparison corrections. Overall, spectral results suggest that enhanced beta desynchronization in older adults reflects a successful compensatory mechanism to cope with increased difficulty during complex interlimb coordination. Functional connectivity results suggest that theta and alpha band connectivity are prone to respectively task- and age-related modulations. Future work could target these spectral and functional connectivity dynamics through noninvasive brain stimulation to potentially improve interlimb coordination in older adults.

Aging and Complexity Effects on Hemisphere-Dependent Movement-Related Beta Desynchronization during Bimanual Motor Planning and Execution.

With aging comes degradation of bimanual movement performance. A hallmark feature of bimanual movements is movement-related beta desynchronization (MRBD), an attenuation in the amplitude of beta oscillations associated with sensorimotor activation. Here, we investigated MRBD in 39 healthy adults (20 younger and 19 older adults) in frontal, central, and parietal regions across both hemispheres, during the planning and execution of a bimanual tracking task. Task accuracy decreased with age and during more difficult conditions when both hands had to move at different relative speeds. MRBD was mostly situated in the central region, and increased in older versus younger adults during movement execution but not planning. Irrespective of age, motor planning and execution were associated with increased MRBD in the left and right hemispheres, respectively. Notably, right central MRBD during motor planning was associated with bimanual task performance, particularly in older adults. Specifically, persons who demonstrated high MRBD during motor planning performed better on the bimanual tracking task. Our results highlight the importance of lateralized MRBD during motor planning, thereby shining new light on previous research and providing a promising avenue for future interventions.