Transcranial magnetic stimulation over supramarginal gyrus stimulates primary motor cortex directly and impairs manual dexterity: implications for TMS focality.

Based on human motor cortex, the effective spatial resolution of transcranial magnetic stimulation (TMS) is often described as 5-20 mm, because small changes in TMS coil position can have large effects on motor-evoked potentials (MEPs). MEPs are often studied at rest, with muscles relaxed. During muscle contraction and movement, corticospinal excitability is higher, thresholds for effective stimulation are lower, and MEPs can be evoked from larger regions of scalp, so the effective spatial resolution of TMS is larger. We found that TMS over the supramarginal gyrus (SMG) impaired manual dexterity in the grooved pegboard task. It also resulted in short-latency MEPs in hand muscles, despite the coil being 55 mm away from the motor cortex hand area (M1). MEPs might be evoked by either a specific corticospinal connection from SMG or a remote but direct electromagnetic stimulation of M1. To distinguish these alternatives, we mapped MEPs across the scalp during rest, isotonic contraction, and manual dexterity tasks and ran electric field simulations to model the expected M1 activation from 27 scalp locations and four coil orientations. We also systematically reviewed studies using TMS during movement. Across five experiments, TMS over SMG reliably evoked MEPs during hand movement. These MEPs were consistent with direct M1 stimulation and substantially decreased corticospinal thresholds during natural movement. Systematic review suggested that 54 published experiments may have suffered from similar motor activation confounds. Our results have implications for the assumed spatial resolution of TMS, and especially when TMS is presented within 55 mm of the motor cortex.NEW & NOTEWORTHY Transcranial magnetic stimulation (TMS) is often described as having an effective spatial resolution of ∼10 mm, because of the limited area of the scalp on which TMS produces motor-evoked potentials (MEPs) in resting muscles. We find that during natural hand movement TMS evokes MEPs from a much larger scalp area, in particular when stimulating over the supramarginal gyrus 55 mm away. Our results show that TMS can be effective at much larger distances than generally assumed.

Online updating of obstacle positions when intercepting a virtual target.

People rely upon sensory information in the environment to guide their actions. Ongoing goal-directed arm movements are constantly adjusted to the latest estimate of both the target and hand's positions. Does the continuous guidance of ongoing arm movements also consider the latest visual information of the position of obstacles in the surrounding? To find out, we asked participants to slide their finger across a screen to intercept a laterally moving virtual target while moving through a gap that was created by two virtual circular obstacles. At a fixed time during each trial, the target suddenly jumped slightly laterally while still continuing to move. In half the trials, the size of the gap changed at the same moment as the target jumped. As expected, participants adjusted their movements in response to the target jump. Importantly, the magnitude of this response depended on the new size of the gap. If participants were told that the circles were irrelevant, changing the gap between them had no effect on the responses. This shows that obstacles' instantaneous positions can be considered when visually guiding goal-directed movements.

Spatial contextual cues that help predict how a target will accelerate can be used to guide interception.

Objects in one's environment do not always move at a constant velocity but often accelerate or decelerate. People are very poor at visually judging acceleration and normally make systematic errors when trying to intercept accelerating objects. If the acceleration is perpendicular to the direction of motion, it gives rise to a curved path. Can spatial contextual cues help one predict such accelerations and thereby help interception? To answer this question, we asked participants to hit a target that moved as if it were attached to a rolling disk, like a valve (target) on a bicycle wheel (disk) moves when cycling: constantly accelerating toward the wheel's center. On half the trials, the disk was visible such that participants could use the spatial relations between the target and the rolling disk to guide their interception. On the other half, the disk was not visible, so participants had no help in predicting the target's complicated pattern of accelerations and decelerations. Importantly, the target's path was the same in both cases. Participants hit more targets when the disk was visible than when it was invisible, even when using a strategy that can compensate for neglecting acceleration. We conclude that spatial contextual cues that help predict the target's accelerations can help intercept it.

The influences of target size and recent experience on the vigour of adjustments to ongoing movements.

People adjust their on-going movements to changes in the environment. It takes about 100 ms to respond to an abrupt change in a target's position. Does the vigour of such responses depend on the extent to which responding is beneficial? We asked participants to tap on targets that jumped laterally once their finger started to move. In separate blocks of trials the target either remained at the new position so that it was beneficial to respond to the jump, or jumped back almost immediately so that it was disadvantageous to do so. We also varied the target's size, because a smaller, less vigorous adjustment is enough to place the finger within a larger target. There was a systematic relationship between the vigour of the response and the remaining time until the tap: the shorter the remaining time the more vigorous the response. This relationship did not depend on the target's size or whether or not the target jumped back. It was already known that the vigour of responses to target jumps depends on the magnitude of the jump and on the time available for adjusting the movement to that jump. We show that the vigour of the response is precisely tuned to the time available for making the required adjustment irrespective of whether responding in this manner is beneficial.

How similar are responses to background motion and target displacements?

When making a goal-directed movement towards a target, our hand follows abrupt background motion. This response resembles that of a shift in the target's position. Does background motion simply change the position towards which the movement is guided? If so, the response to background motion should resemble the response to a target displacement. To find out whether this is the case, we ran two exploratory studies where we asked participants to hit a moving target at a specified moment. At various times during the hand's movement, the background could move briefly at one of several speeds, and for various durations. The response to abrupt background motion was larger when the background moved later in the movement and when the background moved faster, in line with known responses to target displacements. The response to a second epoch of background motion was smaller than it would have been if there had been no first epoch, in contrast to responses to multiple target displacements. If the background was already moving before the target appeared, the hand even moved in the opposite direction. Thus, the response to background motion and that to a target displacement are clearly not identical, but they do share several features.

Gravity Influences How We Expect a Cursor to Move.

We expect a cursor to move upwards when we push our computer mouse away. Do we expect it to move upwards on the screen, upwards with respect to our body, or upwards with respect to gravity? To find out, we asked participants to perform a simple task that involved guiding a cursor with a mouse. It took participants that were sitting upright longer to reach targets with the cursor if the screen was tilted, so not only directions on the screen are relevant. Tilted participants' performance was indistinguishable from that of upright participants when the screen was tilted slightly in the same direction. Thus, the screen's orientation with respect to both the body and gravity are relevant. Considering published estimates of the ocular counter-roll induced by head tilt, it is possible that participants actually expect the cursor to move in a certain direction on their retina.

Further Evidence That People Rely on Egocentric Information to Guide a Cursor to a Visible Target.

Everyday movements are guided by objects' positions relative to other items in the scene (allocentric information) as well as by objects' positions relative to oneself (egocentric information). Allocentric information can guide movements to the remembered positions of hidden objects, but is it also used when the object remains visible? To stimulate the use of allocentric information, the position of the participant's finger controlled the velocity of a cursor that they used to intercept moving targets, so there was no one-to-one mapping between egocentric positions of the hand and cursor. We evaluated whether participants relied on allocentric information by shifting all task-relevant items simultaneously leaving their allocentric relationships unchanged. If participants rely on allocentric information they should not respond to this perturbation. However, they did. They responded in accordance with their responses to each item shifting independently, supporting the idea that fast guidance of ongoing movements primarily relies on egocentric information.

Can ongoing movements be guided by allocentric visual information when the target is visible?

People use both egocentric (object-to-self) and allocentric (object-to-object) spatial information to interact with the world. Evidence for allocentric information guiding ongoing actions stems from studies in which people reached to where targets had previously been seen while other objects were moved. Since egocentric position judgments might fade or change when the target is removed, we sought for conditions in which people might benefit from relying on allocentric information when the target remains visible. We used a task that required participants to intercept targets that moved across a screen using a cursor that represented their finger but that moved by a different amount in a different plane. During each attempt, we perturbed the target, cursor, or background individually or all three simultaneously such that their relative positions did not change and there was no need to adjust the ongoing movement. An obvious way to avoid responding to such simultaneous perturbations is by relying on allocentric information. Relying on egocentric information would give a response that resembles the combined responses to the three isolated perturbations. The hand responded in accordance with the responses to the isolated perturbations despite the differences between how the finger and cursor moved. This response remained when the simultaneous perturbation was repeated many times, suggesting that participants hardly relied upon allocentric spatial information to control their ongoing visually guided actions.

The response to background motion: Characteristics of a movement stabilization mechanism.

When making goal-directed movements toward a target, our hand deviates from its path in the direction of sudden background motion. We propose that this manual following response arises because ongoing movements are constantly guided toward the planned movement endpoint. Such guidance is needed to compensate for modest, unexpected self-motion. Our proposal is that the compensation for such self-motion does not involve a sophisticated analysis of the global optic flow. Instead, we propose that any motion in the vicinity of the planned endpoint is attributed to the endpoint's egocentric position having shifted in the direction of the motion. The ongoing movement is then stabilized relative to the shifted endpoint. In six experiments, we investigate what aspects of motion determine this shift of planned endpoint. We asked participants to intercept a moving target when it reached a certain area. During the target's motion, background structures briefly moved either leftward or rightward. Participants' hands responded to background motion even when each background structure was only briefly visible or when the vast majority of background structures remained static. The response was not restricted to motion along the target's path but was most sensitive to motion close to where the target was to be hit, both in the visual field and in depth. In this way, a movement stabilization mechanism provides a comprehensive explanation of many aspects of the manual following response.

Examining the roles of working memory and visual attention in multiple object tracking expertise.

When tracking multiple moving targets among visually similar distractors, human observers are capable of distributing attention over several spatial locations. It is unclear, however, whether capacity limitations or perceptual-cognitive abilities are responsible for the development of expertise in multiple object tracking. Across two experiments, we examined the role of working memory and visual attention in tracking expertise. In Experiment 1, individuals who regularly engaged in object tracking sports (soccer and rugby) displayed improved tracking performance, relative to non-tracking sports (swimming, rowing, running) (p = 0.02, ηp2 = 0.163), but no differences in gaze strategy (ps > 0.31). In Experiment 2, participants trained on an adaptive object tracking task showed improved tracking performance (p = 0.005, d = 0.817), but no changes in gaze strategy (ps > 0.07). They did, however, show significant improvement in a working memory transfer task (p < 0.001, d = 0.970). These findings indicate that the development of tracking expertise is more closely linked to processing capacity limits than perceptual-cognitive strategies.

Slightly perturbing the arm influences choices between multiple targets.

We constantly make choices about how to interact with objects in the environment. Do we immediately consider changes in our posture when making such choices? To find out, we examined whether motion in the background, which is known to influence the trajectory of goal-directed hand movements, influences participants' choices when suddenly faced with two options. The participants' task was to tap on as many sequentially presented targets as possible within 90 seconds. Sometime after a new target appeared, it split into two targets and participants had to choose which of them to hit. Shortly before the split, the background moved in a way that was expected to result in the finger shifting slightly towards one of the two new targets. We examined whether such shifts influenced the choice between the two targets. The moving background influenced the finger movements in the expected manner: participants moved in the direction of the background motion. It also influenced the choice that participants made between the two targets: participants more frequently chose the target in the direction of the background motion. There was a positive correlation across participants between the magnitude of the response to background motion and the bias to choose the target in the direction of such motion. Thus, people consider sudden changes in their posture when choosing between different movement options.

Hand movements respond to any motion near the endpoint.

Hand movements are pulled in the direction of motion near their planned endpoints. Is this an automatic response to motion signals near those positions, or do we consider what is moving? To find out, we asked participants to hit a target that moved rightward across a patterned surface when it reached an interception zone that was indicated by a circle. The circle was initially at the center of a square. The square was either filled, occluding the patterned surface (tile), or open, such that the patterned surface was not occluded (frame). The square briefly moved leftward or rightward shortly after the target appeared. Thus, participants were either aiming to hit the target on the surface that moved (the tile) or to hit the target on the patterned surface that did not move. Moving the two types of squares produced very similar local motion signals, but for the tile this could be interpreted as motion of an extended surface, while for the frame it could not. Motion onset of the two types of squares yielded very similar responses. Increasing the size of the square, and thus the eccentricity of the local motion signal, reduced the magnitude of the response. Since this reduction was seen for both types of squares, the surface on which the interception zone was presented was clearly not considered. We conclude that the response is driven by local motion signals near the endpoint of the action without considering whether the local surface is moving.

A calming hug: Design and validation of a tactile aid to ease anxiety.

Anxiety disorders affect approximately one third of people during their lifetimes and are the ninth leading cause of global disability. Current treatments focus on therapy and pharmacological interventions. However, therapy is costly and pharmacological interventions often have undesirable side-effects. Healthy people also regularly suffer periods of anxiety. Therefore, a non-pharmacological, intuitive, home intervention would be complementary to other treatments and beneficial for non-clinical groups. Existing at-home anxiety aids, such as guided meditations, typically employ visual and/or audio stimuli to guide the user into a calmer state. However, the tactile sense has the potential to be a more natural modality to target in an anxiety-calming device. The tactile domain is relatively under-explored, but we suggest that there are manifold physiological and affective qualities of touch that lend it to the task. In this study we demonstrate that haptic technology can offer an enjoyable, effective and widely accessible alternative for easing state anxiety. We describe a novel huggable haptic interface that pneumatically simulates slow breathing. We discuss the development of this interface through a focus group evaluating five prototypes with embedded behaviours ('breathing', 'purring', 'heartbeat' and 'illumination'). Ratings indicated that the 'breathing' prototype was most pleasant to interact with and participants described this prototype as 'calming' and 'soothing', reminding them of a person breathing. This prototype was developed into an ergonomic huggable cushion containing a pneumatic chamber powered by an external pump allowing the cushion to 'breathe'. A mixed-design experiment (n = 129) inducing anxiety through a group mathematics test found that the device was effective at reducing pre-test anxiety compared to a control (no intervention) condition and that this reduction in anxiety was indistinguishable from that of a guided meditation. Our findings highlight the efficacy of this interface, demonstrating that haptic technologies can be effective at easing anxiety. We suggest that the field should be explored in more depth to capture the nuances of different modalities in relation to specific situations and trait characteristics.

Motion disrupts dynamic visual search for an orientation change.

Visual search in dynamic environments, for example lifeguarding or CCTV monitoring, has several fundamentally different properties to standard visual search tasks. The visual environment is constantly moving, a range of items could become targets and the task is to search for a certain event. We developed a novel task in which participants were required to search static and moving displays for an orientation change thus capturing components of visual search, multiple object tracking and change detection paradigms. In Experiment 1, we found that the addition of moving distractors slowed participants' response time to detect an orientation changes in a moving target, showing that the motion of distractors disrupts the rapid detection of orientation changes in a moving target. In Experiment 2 we found that, in displays of both moving and static objects, response time was slower if a moving object underwent a change than if a static object did, thus demonstrating that motion of the target itself also disrupts the detection of an orientation change. Our results could have implications for training in real-world occupations where the task is to search a dynamic environment for a critical event. Moreover, we add to the literature highlighting the need to develop lab-based tasks with high experimental control from any real-world tasks researchers may wish to investigate rather than extrapolating from static visual search tasks to more dynamic environments.

Transfer effects in auditory temporal preparation occur using an unfilled but not filled foreperiod.

How quickly participants respond to a "go" after a "warning" signal is partly determined by the time between the two signals (the foreperiod) and the distribution of foreperiods. According to Multiple Trace Theory of Temporal Preparation (MTP), participants use memory traces of previous foreperiods to prepare for the upcoming go signal. If the processes underlying temporal preparation reflect general encoding and memory principles, transfer effects (the carryover effect of a previous block's distribution of foreperiods to the current block) should be observed regardless of the sensory modality in which signals are presented. Despite convincing evidence for transfer effects in the visual domain, only weak evidence for transfer effects has been documented in the auditory domain. Three experiments were conducted to examine whether such differences in results are due to the modality of the stimulus or other procedural factors. In each experiment, two groups of participants were exposed to different foreperiod distributions in the acquisition phase and to the same foreperiod distribution in the transfer phase. Experiment 1 used a choice-reaction time (RT) task, and the warning signal remained on until the go signal, but there was no evidence for transfer effects. Experiments 2 and 3 used a simple- and choice-RT task, respectively, and there was silence between the warning and go signals. Both experiments revealed evidence for transfer effects, which suggests that transfer effects are most evident when there is no auditory stimulation between the warning and go signals.

Learning a reach trajectory based on binary reward feedback.

Binary reward feedback on movement success is sufficient for learning some simple sensorimotor mappings in a reaching task, but not for some other tasks in which multiple kinematic factors contribute to performance. The critical condition for learning in more complex tasks remains unclear. Here, we investigate whether reward-based motor learning is possible in a multi-dimensional trajectory matching task and whether simplifying the task by providing feedback on one factor at a time ('factorized feedback') can improve learning. In two experiments, participants performed a trajectory matching task in which learning was measured as a reduction in the error. In Experiment 1, participants matched a straight trajectory slanted in depth. We factorized the task by providing feedback on the slant error, the length error, or on their composite. In Experiment 2, participants matched a curved trajectory, also slanted in depth. In this experiment, we factorized the feedback by providing feedback on the slant error, the curvature error, or on the integral difference between the matched and target trajectory. In Experiment 1, there was anecdotal evidence that participants learnt the multidimensional task. Factorization did not improve learning. In Experiment 2, there was anecdotal evidence the multidimensional task could not be learnt. We conclude that, within a complexity range, multiple kinematic factors can be learnt in parallel.

In-task auditory performance-related feedback promotes cardiovascular markers of a challenge state during a pressurized task.

Background and Objectives: Individuals evaluate the demands and resources associated with a pressurized situation, which leads to distinct patterns of cardiovascular responses. While it is accepted that cognitive evaluations are updated throughout a pressurized situation, to date, cardiovascular markers have only been recorded immediately before, or averaged across, these situations. Thus, this study examined the influence of in-task performance-related feedback on cardiovascular markers of challenge and threat to explore fluctuations in these markers. Methods and Design: Forty participants completed a pressurized visual search task while cardiovascular markers of challenge and threat were recorded. During the task, participants received either positive or negative feedback via distinct auditory tones to induce a challenge or threat state. Following task completion, cardiovascular markers were recorded during a recovery phase. Results: Participants' cardiovascular responses changed across the experimental protocol. Specifically, while participants displayed a cardiovascular response more reflective of a challenge state following in-task performance-related feedback, participants exhibited a response more akin to a threat state later during the recovery phase. Conclusions: In-task auditory performance-related feedback promoted cardiovascular markers of a challenge state. These markers fluctuated over the experiment, suggesting that they, and presumably underlying demand and resource evaluations, are relatively dynamic in nature.

Visual spatial attention and spatial working memory do not draw on shared capacity-limited core processes.

The extent to which similar capacity limits in visual attention and visual working memory indicate a common shared underlying mechanism is currently still debated. In the spatial domain, the multiple object tracking (MOT) task has been used to assess the relationship between spatial attention and spatial working memory though existing results have been inconclusive. In three dual task experiments, we examined the extent of interference between attention to spatial positions and memory for spatial positions. When the position monitoring task required keeping track of target identities through colour-location binding, we found a moderate detrimental effect of position monitoring on spatial working memory and an ambiguous interaction effect. However, when this task requirement was removed, load increases in neither task were detrimental to the other. The only very moderate interference effect that remained resided in an interaction between load types but was not consistent with shared capacity between tasks-rather it was consistent with content-related crosstalk between spatial representations. Contrary to propositions that spatial attention and spatial working memory may draw on a common shared set of core processes, these findings indicate that for a purely spatial task, perceptual attention and working memory appear to recruit separate core capacity-limited processes.

Evidence for short-term, but not long-term, transfer effects in the temporal preparation of auditory stimuli.

Starting procedures in racing sports consist of a warning (e.g., "Set") followed by a target (e.g., "Go") signal. During this interval (the foreperiod), athletes engage in temporal preparation whereby they prepare to respond to the target as quickly as possible. Despite a long history, the cognitive mechanisms underlying this process are debated. Recently, it has been suggested that traces of previous temporal durations drive temporal preparation performance rather than the traditional explanation that performance is related to the currently perceived hazard function. Los and colleagues used visual stimuli for the warning and target signals. As racing sports typically rely upon auditory stimuli, we investigated the role of memory on temporal preparation in the auditory domain. Experiment 1 investigated long-term transfer effects. In an acquisition phase, two groups of participants were exposed to different foreperiod distributions. One week later, during a transfer phase, both groups received the same distribution of foreperiods. There was no evidence for transfer effects. Therefore, Experiment 2 examined short-term transfer effects in which acquisition and transfer phases were completed in the same testing session. There was some evidence for transfer effects, but this was limited, suggesting that there may be modality-specific memory differences.

Goal-directed unequal attention allocation during multiple object tracking.

In standard multiple object tracking (MOT) tasks the relative importance of the targets being tracked is equal. This is atypical of everyday situations in which an individual may need to prioritize one target relative to another and so allocate attention unequally. We report three experiments that examined whether participants could unequally split attention using a modified MOT task in which target priority was manipulated. Specifically, we examined the effect of priority on participants' magnitude of error and used a distribution mixture analysis to investigate how priority affected both participants' probability of losing an item and tracking precision. Experiment 1 (trajectory tracking) revealed a higher magnitude of error and higher proportion of guessing for low- compared with high-priority targets. Experiments 2 (trajectory tracking) and 3 (position tracking) examined how fine-grained this ability is by manipulating target priority at finer increments. In line with Experiment 1, results from both these experiments indicated that participants could split attention unequally. There was some evidence that participants could allocate attention unequally at fine increments, but this was less conclusive. Taken together, these experiments demonstrate participants' ability to distribute attention unequally across multiple moving objects but suggest some limitation with the flexibility of attention allocation.