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Movement Preparation (movement + preparation)
Selected AbstractsPrepare for conflict: EEG correlates of the anticipation of target competition during overt and covert shifts of visual attentionEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2010Simon P. Kelly Abstract When preparing to make a saccadic eye movement in a cued direction, perception of stimuli at the target location is enhanced, just as it is when attention is covertly deployed there. Accordingly, the timing and anatomical sources of preparatory brain activity accompanying shifts of covert attention and saccade preparation tend to exhibit a large degree of overlap. However, there is evidence that preparatory processes are modulated by the foreknowledge of visual distractor competition during covert attention, and it is unknown whether eye movement preparation undergoes equivalent modulation. Here we examine preparatory processes in the electroencephalogram of human participants during four blocked versions of a spatial cueing task, requiring either covert detection or saccade execution, and either containing a distractor or not. As in previous work, a typical pattern of spatially selective occipital, parietal and frontal activity was seen in all task versions. However, whereas distractor presence called on an enhancement of spatially selective visual cortical modulation during covert attention, it instead called on increased activity over frontomedial oculomotor areas in the case of overt saccade preparation. We conclude that, although advance orienting signals may be similar in character during overt and covert conditions, the pattern by which these signals are modulated to ameliorate the behavioral costs of distractor competition is highly distinct, pointing to a degree of separability between the overt and covert systems. [source] Temporal dynamics of ipsilateral and contralateral motor activity during voluntary finger movementHUMAN BRAIN MAPPING, Issue 1 2004Ming-Xiong Huang Abstract The role of motor activity ipsilateral to movement remains a matter of debate, due in part to discrepancies among studies in the localization of this activity, when observed, and uncertainty about its time course. The present study used magnetoencephalography (MEG) to investigate the spatial localization and temporal dynamics of contralateral and ipsilateral motor activity during the preparation of unilateral finger movements. Eight right-handed normal subjects carried out self-paced finger-lifting movements with either their dominant or nondominant hand during MEG recordings. The Multi-Start Spatial Temporal multi-dipole method was used to analyze MEG responses recorded during the movement preparation and early execution stage (,800 msec to +30 msec) of movement. Three sources were localized consistently, including a source in the contralateral primary motor area (M1) and in the supplementary motor area (SMA). A third source ipsilateral to movement was located significantly anterior, inferior, and lateral to M1, in the premotor area (PMA) (Brodmann area [BA] 6). Peak latency of the SMA and the ipsilateral PMA sources significantly preceded the peak latency of the contralateral M1 source by 60 msec and 52 msec, respectively. Peak dipole strengths of both the SMA and ipsilateral PMA sources were significantly weaker than was the contralateral M1 source, but did not differ from each other. Altogether, the results indicated that the ipsilateral motor activity was associated with premotor function, rather than activity in M1. The time courses of activation in SMA and ipsilateral PMA were consistent with their purported roles in planning movements. Hum. Brain Mapp. 23:26,39, 2004. © 2004 Wiley-Liss, Inc. [source] The instructed context of a motor task modulates covert response preparation and shifts of spatial attentionPSYCHOPHYSIOLOGY, Issue 3 2009Elena Gherri Abstract We investigated how covert response preparation is modulated by the instructed cognitive context of a motor task. Participants prepared left-hand or right-hand movements toward or away from the body midline, as indicated by a response cue (S1) presented prior to a go/no-go stimulus (S2). Different participants were instructed that response cues specified the response hand or movement direction, respectively. This emphasis on effector versus movement direction selection modulated lateralized ERP components triggered during the S1,S2 interval. Attention shifts during movement preparation were assessed by measuring ERPs to irrelevant visual probes. Enhanced N1 components were found for probes near the effector when effector selection was emphasized, but for probes near the movement target location when movement direction selection was emphasized. Results demonstrate strong top-down contextual biases on motor control and on the locus of spatial attention during response preparation. [source] Excitability of human motor cortex inputs prior to graspTHE JOURNAL OF PHYSIOLOGY, Issue 1 2007Gita Prabhu Transcranial magnetic stimulation (TMS) was used to investigate corticospinal excitability during the preparation period preceding visually guided self-paced grasping. Previously we have shown that while subjects prepare to grasp a visible object, paired-pulse TMS at a specific interval facilitates motor-evoked potentials (MEPs) in hand muscles in a manner that varies with the role of the muscle in shaping the hand for the upcoming grasp. This anticipatory modulation may reflect transmission of inputs to human primary motor cortex (M1) for visuomotor guidance of hand shape. Conversely, single-pulse TMS is known to suppress MEPs during movement preparation. Here we investigate the time course of single- and paired-pulse MEP modulation. TMS was delivered over M1, at different time intervals after visual presentation of either a handle or a disc to healthy subjects. Participants were instructed to view the object, and later to grasp it when given a cue. During grasp there was a specific pattern of hand muscle activity according to the object grasped. MEPs were evoked in these muscles by TMS delivered prior to grasp. Paired-pulse MEPs were facilitated, whilst single-pulse MEPs were suppressed. The pattern of facilitation matched the object-specific pattern of muscle activity for TMS pulses delivered 150 ms or more after object presentation. However, this effect was not present when TMS was delivered immediately after object presentation, or if the delivery of TMS was given separately from the cue to perform the grasp action. These results suggest that object-related information for preparation of appropriate hand shapes reaches M1 only immediately preceding execution of the grasp. [source] | ||||||||||