Visually guided movement with increasing time-on-task: Differential effects on movement preparation and movement execution.

This study tested the reactivity of motor cortex inhibition to different intensities of external stimulation by transcranial magnetic stimulation (TMS) and its internal modulation during different motor states in children and adolescents with Tourette syndrome. TMS-evoked N100 served as an indirect measure of GABAB receptor function which is related to cortical inhibition. Combined TMS/EEG was used to analyze the TMS-evoked N100 component evoked by different stimulation intensities as well as during resting condition, movement preparation (contingent negative variation task) and movement execution. The study included 18 early adolescents with Tourette syndrome and 15 typically developing control subjects. TMS-evoked N100 showed a less steep increase with increasing TMS intensity in Tourette syndrome together with less modulation (disinhibition) over the primary motor cortex during the motor states movement preparation and movement execution. Children with Tourette syndrome showed equally high N100 amplitudes at 110% resting motor threshold (RMT) intensity during resting condition and a parallel decline of RMT and N100 amplitude with increasing age as control subjects. Our study yields preliminary evidence that modulation of motor cortical inhibitory circuits, during external direct stimulation by different TMS intensities and during volitional movement preparation and execution is different in children and adolescents with Tourette syndrome compared to controls. These results suggest that a reduced resting motor cortical inhibitory "reserve" could contribute to the production of unwanted movements. Our findings are compatible with increased regulation of motor cortex excitability by perception-action binding in Tourette syndrome instead of top-down / motor regulation and need to be replicated in further studies.

Movement-related potentials (MRPs) associated with voluntary movements reflect cortical activity associated with processes of movement preparation and movement execution. Early-stage pre-movement activity is reduced in amplitude in Parkinson's disease. However, it is unclear whether this neurophysiological deficit relates to preparatory or execution-related activity, since previous studies have not been able to separate different functional components of MRPs. Motor imagery is thought to involve mainly processes of movement preparation, with reduced involvement of end-stage movement execution-related processes. Therefore, MRP components relating to movement preparation and execution may be examined separately by comparing MRPs associated with imagined and actual movements. In this study, MRPs were recorded from 14 subjects with Parkinson's disease and 10 age-matched control subjects while they performed a sequential button-pressing task, and while they imagined performance of the same task. Early-stage pre-movement activity was present in both Parkinson's disease patients and control subjects when they imagined movement, but was reduced in amplitude compared with that for actual movement. Movement execution-related components, arising predominantly from the primary motor cortex, were relatively unaffected in Parkinson's disease subjects. However, motor preparatory processes, probably involving the supplementary motor area, were reduced in amplitude overall and abnormally prolonged, indicating impaired termination following the motor response. Further, this impaired termination of preparatory-phase activity was observed only in patients with more severe parkinsonian symptoms, and not in early-stage Parkinson's disease.

Motor cortical neurons are activated during movement preparation and execution, and in response to task-relevant visual cues. A few studies also report activation before the expected presentation of cues. Here, we study specifically this anticipatory activity preceding visual cues in motor cortical areas. We recorded the activity of 1215 neurons in the motor cortex of two macaque monkeys while they performed a center-out reaching task, including two consecutive delays of equal duration, known in advance. During the first delay (D1), they had to await the spatial cue and only reach to the cued target after the second delay (D2). Forty-two percent of the neurons displayed anticipatory activity during D1. Among these anticipatory neurons, 59% increased (D1up) their activity and the remaining decreased (D1down) their activity. By classifying the neurons according to these firing rate profiles during D1, we found that the activity during D2 differed in a systematic way. The D1up neurons were more likely to discharge phasically soon after the spatial cue and were less active during movement execution, whereas the D1down neurons showed the opposite pattern. But, regardless of their temporal activity profiles, the two categories seemed equally involved in early and late motor preparation, as reflected in their directional selectivity. This precue activity in motor cortex may reflect two complementary, coexisting processes: the facilitation of incoming spatial information in parallel with the downregulation of corticospinal excitability to prevent a premature response.

BackgroundIn Gilles de la Tourette syndrome (GTS) increased activation of the primary motor cortex (M1) before and during movement execution followed by increased inhibition after movement termination was reported. The present study aimed at investigating, whether this activation pattern is due to altered functional interaction between motor cortical areas.Methodology/Principal Findings10 GTS-patients and 10 control subjects performed a self-paced finger movement task while neuromagnetic brain activity was recorded using Magnetoencephalography (MEG). Cerebro-cerebral coherence as a measure of functional interaction was calculated. During movement preparation and execution coherence between contralateral M1 and supplementary motor area (SMA) was significantly increased at beta-frequency in GTS-patients. After movement termination no significant differences between groups were evident.Conclusions/SignificanceThe present data suggest that increased M1 activation in GTS-patients might be due to increased functional interaction between SMA and M1 most likely reflecting a pathophysiological marker of GTS. The data extend previous findings of motor-cortical alterations in GTS by showing that local activation changes are associated with alterations of functional networks between premotor and primary motor areas. Interestingly enough, alterations were evident during preparation and execution of voluntary movements, which implies a general theme of increased motor-cortical interaction in GTS.

Comparison of monosynaptic tendon reflexes during preparation for ballistic or ramp movement

Clinical and neurophysiological monitoring and head injury patients with diffuse axonal injury

The posterior parietal cortex is involved in the visuomotor transformations occurring during arm-reaching movements. The medial posterior parietal area V6A has been shown to be implicated in reaching execution, but its role in reaching preparation has not been sufficiently investigated. Here, we addressed this issue exploring the neural correlates of reaching preparation in V6A. Neural activity of single cells during the instructed delay period of a foveated Reaching task was compared with the activity in the same delay period during a Detection task. In this latter task, animals fixated the target but, instead of performing an arm reaching movement, they responded with a button release to the go signal. Targets were allocated in different positions in 3-D space. We found three types of neurons: cells where delay activity was equally spatially tuned in the two tasks (Gaze cells), cells spatially tuned only during reaching preparation (Set cells), and cells influenced by both gaze and reaching preparation signals (Gaze/Set cells). In cells influenced by reaching preparation, the delay activity in the Reaching task could be higher or lower compared with the Detection task. All the Set cells and a minority of Gaze/Set cells were more active during reaching preparation. Most cells modulated by movement preparation were also modulated with a congruent spatial tuning during movement execution. Present results highlight the convergence of visuospatial information, reach planning and reach execution signals on V6A, and indicate that visuospatial processing and movement execution have a larger influence on V6A activity than the encoding of reach plans.

Motor intention in the posterior parietal cortex

Beta-band power modulation in the human amygdala during a delayed reach task.

Brain Update provides practicing nurses with featured aspects of brain biology. PPC offers this feature in an effort to enable nurses to integrate brain biology into their practice. The purpose of this column is to focus on the biological causes of mental illness. Topics of future columns will include the limbic system, the extraphyramidal system, and the role of biology in schizophrenia. Key words: Basal ganglia, caudate nucleus, globus pallidus, lentiform nucleus, putamen, striatum The basal ganglia are a group of subcortical nuclei that lie below the outer rim of brain gray matter. The basal ganglia are composed of three major nuclei: the caudate nucleus, the putamen, and the globus pallidus (Figure 1). Other authors include the subthalamic and substantia nigra nuclei (Kandler, Schwartz, & Jessell, 1991). The caudate and putamen are collectively referred to as the striatum, while the putamen and globus pallidus are referred to as the lentiform nucleus. The basal ganglia, which are located deep within the brain, bridge the cerebral cortex, the diencephalon (various thalamic nuclei), and the midbrain. Visible only when the brain is cut, the basal ganglia are rich both with afferent and efferent projections. Most input (afferent) projections arise from the cerebral cortex, while output (efferent) projections are directed first to the thalamus and then to the prefrontal, premotor, and motor areas of the cortex (Albin, Young, & Penney, 1995; Zweig, 1995). These connections are named in such a way as to identify the beginning and ending point of a particular projection. For example, the striatopallidal pathway begins in the striatum and ends in the globus pallidus; the nigrostriatal pathway begins in the substantia nigra and projects to the striatum. These extensive connections and interconnections form a generous network of parallel loops, which underscores the interdependence of these afferent and efferent pathways. Functions of the Basal Ganglia Brooks (1995) lists several functions of the basal ganglia: 1) preparation for movement, 2) inhibition of unwanted movement, 3) adaptation to novel circumstances, 4) facilitation of reward actions, and 5) promotion of motor learning and planning. Given that basal ganglia projections reach the prefrontal, premotor, and motor cortices, the dysfunctions associated with basal ganglia pathology have clarified that these nuclei are part of the extrapyramidal system. The pyramidal system, or corticospinal tract, begins in the motor area of the cortex and is responsible for voluntary movement. The extrapyramidal system supports the pyramidal system primarily through the preparation for and execution of movement (Middleton & Strick, 1994). Movement disorders occur when extrapyramidal influences are lifted. Basal ganglia also may facilitate reward activities of the brain. Apparently, the use of cocaine affects the uptake and release of basal ganglia catecholamines, including dopamine (Graybiel, 1995). Catecholamine flooding causes intense perceptions of pleasure and is addicting in the broader sense of the word. The basal ganglia, with their rich connectivity to frontal areas, also play a role in cognitive function. Verbal fluency, card sorting, planning, and spatial and digit working memory are impaired in clients with known basal ganglia deficits (e.g., parkinsonism) (Brooks, 1995). Graybiel (1995) ponders whether movement disorders have analogues in thought control disorders, such as obsessive-compulsive disorder (OCD). Tics, a group of stereotyped repetitive motor disorders that have both motor and cognitive components, are sometimes associated with OCD (Albin et al., 1995). For example, uncontrolled verbal obscenities are part of the symptoms found in clients with Tourette's syndrome. Disorders of the Basal Ganglia Most knowledge of basal ganglia function stems from postmortem examination of basal ganglia nuclei in Parkinson and Huntington's disorder clients. …

Event-related coherence and event-related desynchronization/synchronization in the 10 Hz and 20 Hz EEG during self-paced movements

Hand, Space and Attentional Asymmetries in Goal-Directed Manual Aiming

Deep neural networks (DNNs) are widely adopted to decode motor states from both non-invasively and invasively recorded neural signals, e.g., for realizing brain-computer interfaces. However, the neurophysiological interpretation of how DNNs make the decision based on the input neural activity is limitedly addressed, especially when applied to invasively recorded data. This reduces decoder reliability and transparency, and prevents the exploitation of decoders to better comprehend motor neural encoding. Here, we adopted an explainable artificial intelligence approach – based on a convolutional neural network and an explanation technique – to reveal spatial and temporal neural properties of reach-to-grasping from single-neuron recordings of the posterior parietal area V6A. The network was able to accurately decode 5 different grip types, and the explanation technique automatically identified the cells and temporal samples that most influenced the network prediction. Grip encoding in V6A neurons already started at movement preparation, peaking during movement execution. A difference was found within V6A: dorsal V6A neurons progressively encoded more for increasingly advanced grips, while ventral V6A neurons for increasingly rudimentary grips, with both subareas following a linear trend between the amount of grip encoding and the level of grip skills. By revealing the elements of the neural activity most relevant for each grip with no a priori assumptions, our approach supports and advances current knowledge about reach-to-grasp encoding in V6A, and it may represent a general tool able to investigate neural correlates of motor or cognitive tasks (e.g., attention and memory tasks) from single-neuron recordings.

Motor disorders increase dramatically with age; however, little is known about non-clinical ageing of motor control mechanisms and their respective neural correlates. With the present experiment we aimed to study age effects on advance movement preparation, a key characteristic of motor behaviour that is known to involve premotor and primary motor circuits. The respective brain regions are subject to age-related brain atrophy of grey and white matter, and we therefore hypothesized that motor preparation mechanisms may be altered in older persons. Using a motor priming paradigm, performance data and event-related potentials were recorded in older (68-83 years) and younger (21-25 years) participants. The effect pattern observed for the younger group fully replicated previous findings, showing significant reaction time benefits and greater foreperiod activity for valid trials, as well as lateralized activation over motor regions. In older participants, the validity effect was insignificant, which corresponded to markedly reduced foreperiod amplitudes and the absence of lateralized activity. At the same time, the event-related potential showed a frontocentrally distributed positive component peaking in the P300 latency range after presentation of the prime. The amplitude of this potential was enhanced in elderly compared with young participants. The data suggest that the information processing related to the anticipation and preparation of an upcoming response changes substantially with age. In contrast to younger participants, older participants show no indication of effector-specific activation and recruit frontal areas in anticipation of a response signal. It is therefore not only movement execution that changes with age but also motor cognition.

Obesity is a debilitating disease of global proportions that necessitates refined, concept-driven therapeutic approaches. Policy makers, the public and even health care professionals, but also individuals with obesity harbour many misconceptions regarding this disease, which leads to prejudice, negative attitudes, stigmatization, discrimination, self-blame, and failure to provide and finance adequate medical care. Decades of intensive, successful scientific research on obesity have only had a very limited effect on this predicament. We propose a science-based, easy-to-understand conceptual model that synthesizes the complex pathogenesis of obesity including biological, psychological, social, economic and environmental aspects with the aim to explain and communicate better the nature of obesity and currently available therapeutic modalities. According to our integrative 'Behavioral Balance Model', 'top-down cognitive control' strategies are implemented (often with limited success) to counterbalance the increased 'bottom-up drive' to gain weight, which is triggered by biological, psycho-social and environmental mechanisms in people with obesity. Besides offering a deeper understanding of obesity, the model also highlights why there is a strong need for multimodal therapeutic approaches that may not only increase top-down control but also reduce a pathologically increased bottom-up drive.