Preparation Of Hand Movements Research Articles

Remember how to use it: Effector-dependent modulation of spatial working memory activity in posterior parietal cortex.

Working memory (WM) is the key process linking perception to action. Several lines of research have, accordingly, highlighted WM's engagement in sensori-motor associations between retrospective stimuli and future behavior. Using human fMRI we investigated whether prior information about the effector used to respond in a WM task would have an impact on the way the same sensory stimulus is maintained in memory despite a behavioral response could not be readily planned. We focused on WM-related activity in posterior parietal cortex during the maintenance of spatial items for a subsequent match-to-sample comparison, which was reported either with a verbal or with a manual response. We expected WM activity to be higher for manual response trials, because of posterior parietal cortex's engagement in both spatial WM and hand movement preparation. Increased fMRI activity for manual response trials in bilateral anterior intraparietal sulcus confirmed our expectations. These results imply that the maintenance of sensory material in WM is optimized for motor context, i.e. for the effector that will be relevant in the upcoming behavioral responses.

Using synchronized eye and motion tracking to determine high-precision eye-movement patterns during object-interaction tasks.

This study explores the role that vision plays in sequential object interactions. We used a head-mounted eye tracker and upper-limb motion capture to quantify visual behavior while participants performed two standardized functional tasks. By simultaneously recording eye and motion tracking, we precisely segmented participants' visual data using the movement data, yielding a consistent and highly functionally resolved data set of real-world object-interaction tasks. Our results show that participants spend nearly the full duration of a trial fixating on objects relevant to the task, little time fixating on their own hand when reaching toward an object, and slightly more time-although still very little-fixating on the object in their hand when transporting it. A consistent spatial and temporal pattern of fixations was found across participants. In brief, participants fixate an object to be picked up at least half a second before their hand arrives at the object and stay fixated on the object until they begin to transport it, at which point they shift their fixation directly to the drop-off location of the object, where they stay fixated until the object is successfully released. This pattern provides additional evidence of a common system for the integration of vision and object interaction in humans, and is consistent with theoretical frameworks hypothesizing the distribution of attention to future action targets as part of eye and hand-movement preparation. Our results thus aid the understanding of visual attention allocation during planning of object interactions both inside and outside the field of view.

Modulation of Functional Connectivity and Activation during Preparation for Hand Movement

OCCUPATIONAL APPLICATIONS Our results illustrate the enhanced functional connectivity between motor-related brain regions and high-level cognitive brain regions during the transition period between rest and hand movements. These results suggest that the sensorimotor network is interacting with prefrontal areas during the transition period to maintain the preparation state. Both actual movement and the transition period without actual movement modulate brain activities. Capturing the detailed relationship of movement intention could be utilized to improve precision and latency of anticipation-based brain–computer interfaces. Furthermore, consistent with the neuroergonomic approach, this study demonstrates that functional near-infrared spectroscopy is a suitable tool for region-specific, task-related, and resting-state functional connectivity analysis. Our findings could enhance the development of more intuitive and natural interfaces between human and machine systems in diverse areas. The approach presented here could help create assistive devices that perceive and predict operators' intention of movements.TECHNICAL ABSTRACT Introduction: Traditional and new generations of neuroimaging techniques allow observing the modulation of brain activities during transition periods between rest and physical movement execution. A thorough understanding of the brain activity and functional connectivity changes during these transitions could contribute to increasing the precision and decreasing the latency of anticipation-based brain–computer interfaces, and improving human-system integration in general. Consistent with the neuroergonomic approach, functional near-infrared spectroscopy can monitor the outer cortex during extensive physical movement and in realistic settings using wearable and portable sensors. Methods: In this study, 19 healthy subjects were monitored with functional near-infrared spectroscopy during rest, a fist opening and closing task, and the transition period preceding the task. Functional connectivity analysis was used to evaluate how the transition period preceding the task modulated the brain activities. Results: There were several increases in functional connectivity during the transition period, especially between the right dorsolateral prefrontal cortex and the contralateral primary somatosensory and primary motor cortices, as well as the functional connectivity connecting the contralateral primary somatosensory cortex with the ipsilateral primary somatosensory cortex and the primary motor cortex. Regions located in the sensorimotor networks and right dorsolateral prefrontal cortex were also found to be activated during the transition period. Conclusions: These results demonstrate that the sensorimotor network is interacting with the high-level cognitive brain network during the transition period to maintain the preparation state. Furthermore, functional near-infrared spectroscopy is an emerging tool well-suited for region specific task-related and resting-state functional connectivity analysis. The results and the approach presented here suggest that operators' intention to move can be detected before the actual movement, and that could be employed for development of more intuitive and natural interfaces between human and machine systems.

Saccade-Related Potentials During Eye-Hand Coordination: Effects of Hand Movements on Saccade Preparation.

This study investigated the effect of hand movements on behavioral and electrophysiological parameters of saccade preparation. While event-related potentials were recorded in 17 subjects, they performed saccades to a visual target either together with a hand movement in the same direction, a hand movement in the opposite direction, a hand movement to a third, independent direction, or without any accompanying hand movements. Saccade latencies increased with any kind of accompanying hand movement. Both saccade and manual latencies were largest when both movements aimed at opposite directions. In contrast, saccade-related potentials indicating preparatory activity were mainly affected by hand movements in the same direction. The data suggest that concomitant hand movements interfere with saccade preparation, particularly when the two movements involve motor preparations that access the same visual stimulus. This indicates that saccade preparation is continually informed about hand movement preparation.

The orienting of attention during eye and hand movements: ERP evidence for similar frame of reference but different spatially specific modulations of tactile processing

To investigate which frames of reference guide shifts of attention triggered during eye and hand movement preparation and the specificity of their effects on somatosensory processing, we recorded event-related brain potentials (ERPs) in a Go/Nogo task where a cue indicated to prepare an eye movement toward – or a hand movement with – the left or right hand. Before the imperative stimulus, a tactile probe was presented to one hand. Spatially selective modulations of tactile processing were more sustained for hand than eye movements, indicating stronger attentional modulations for the modality of the effector's sensory organ. Importantly, attentional modulations of somatosensory processing as well as lateralized ERP components in the preparation interval were virtually identical under uncrossed and crossed hands conditions, suggesting that shifts of attention triggered during hand and eye movement preparation are guided by a common external reference frame.

Eye-hand coordination during reaching. II. An analysis of the relationships between visuomanual signals in parietal cortex and parieto-frontal association projections.

The relationships between the distribution of visuomanual signals in parietal cortex and that of parieto-frontal projections are the subject of the present study. Single cell recording was performed in areas PEc and V6A, where different anatomical tracers were also injected. The monkeys performed a variety of behavioral tasks, aimed at studying the visual and motor properties of parietal cells, as well as the potential combination of retinal-, eye- and hand-related signals on cell activity. The activity of most cells was related to the direction of movement and the active position of the hand. Many of these reach-related cells were influenced by eye position information. Fewer cells displayed relationships to saccadic eye movements. The activity of most neurons related to a combination of both hand and eye signals. Many cells were also modulated during preparation for hand movement. Light-dark differences of activity were common and interpreted as related to the sight and monitoring of hand motion and/or position in the visual field. Most cells studied were very sensitive to moving visual stimuli and also responded to optic flow stimulation. Visual receptive fields were generally large and extended to the periphery of the visual field. For most neurons, the orientation of the preferred directions computed across different epochs and tasks conditions clustered within a limited sector of space, the field of global tuning. This can be regarded as an ideal frame to combine spatially congruent eye- and hand-related information for different forms of visuomanual behavior. All these properties were common to both PEc and V6A. Retinal, eye- and hand-related activity types, as well as parieto-frontal association cells, were distributed in a periodic fashion across the tangential domain of areas PEc and V6A. These functional and anatomical distributions were characterized and compared through a spectral and coherency analysis, which revealed the existence of a selective 'match' between activity types and parieto-frontal connections. This match depended on where each individual efferent projection was addressed. The results of the present and of the companion study can be relevant for a re-interpretation of optic ataxia as the consequence of the breakdown of the combination of retinal-, eye- and hand-related directional signals within the global tuning fields of parietal neurons.

Early coding of reaching in the parietooccipital cortex.

Neural activity was recorded in the parietooccipital cortex while monkeys performed different tasks aimed at investigating visuomotor interactions of retinal, eye, and arm-related signals on neural activity. The tasks were arm reaching 1) to foveated targets; 2) to extrafoveal targets, with constant eye position; 3) within an instructed-delayed paradigm, under both light and darkness; 4) saccadic eye movements toward, and static eye holding on peripheral targets; and 5) visual fixation and stimulation. The activity of many cells was modulated during arm reaction (68%) and movement time (58%), and during static holding of the arm in space (64%), when eye position was kept constant. Eye position influenced the activity of many cells during hand reaction (45%) and movement time (51%) and holding of hand static position (69%). Many cells (56%) were also modulated during preparation for hand movement, in the delayed reach task. Modulation was present also in the dark in 59% of cells during this epoch, 51% during reaction and movement time, and 48% during eye/hand holding on the target. Cells (50%) displaying light-dark differences of activity were considered as related to the sight and monitoring of hand motion and/or position in the visual field. Saccadic eye movements modulated a smaller percentage (25%) of cells than eye position (68%). Visual receptive fields were mapped in 44% of the cells studied. They were generally large and extended to the periphery of the tested (30 degrees ) visual field. Sixty-six percent of cells were motion sensitive. Therefore the activity of many neurons in this area reflects the combined influence of visual, eye, and arm movement-related signals. For most neurons, the orientation of the preferred directions computed across different epochs and tasks, therefore expression of all different eye- and hand-related activity types, clustered within a limited sector of space, the field of global tuning. These spatial fields might be an ideal frame to combine eye and hand signals, thanks to the congruence of their tuning properties. The relationships between cell activity and oculomotor and visuomanual behavior were task dependent. During saccades, most cells were recruited when the eye moved to a spatial location that was also target for hand movement, whereas during hand movement most cells fired depending on whether or not the animal had prior knowledge about the location of the visual targets.

Posterior and Anterior Contribution of Hand-Movement Preparation to Late CNV

Abstract The late part of the Contingent Negative Variation (CNV) is assumed to be a composite potential, reflecting both movement preparation and several other processes. To assess the contribution of hand-motor preparation to overall CNV, three S1-S2 experiments were performed. Replicating earlier results that have been interpreted as demonstrating hand-motor preparation, experiment 1 showed that CNV gets larger centro-parietally under speed instruction. Experiments 2 and 3 compared preparation for hand responses (key-press) to preparation for ocular responses (saccades) varying the effector system either between blocks (exp. 2) or between trials (exp. 3) and also comparing these preparation situations to no preparation (exp. 3). Hand-motor preparation was reflected in CNV getting larger fronto-centrally, with this topography being significantly different from the effect in experiment 1. Thus, two different kinds of motor preparation appear to be reflected by CNV. One kind may consist of assembling and maintaining the stimulus-response links appropriate to the expected S2 patterns, the other is for activating the hand-motor area. These two motor contributions to CNV might reflect the two aspects of the parieto-frontal motor system.