Location but not amount of stimulus occlusion influences the stability of visuo-motor coordination

The current study examined whether the amount and location of available movement information influenced the stability of visuo-motor coordination. Participants coordinated a hand-held pendulum with an oscillating visual stimulus in an inphase and antiphase manner. The effects of occluding different amounts of phase at different phase locations were examined. Occluding the 0°/180° phase locations (end-points) significantly increased the variability of the visuo-motor coordination. The amount of occlusion had little or no affect on the stability of the coordination. We concluded that the end-points of a visual rhythm are privileged and provide access to movement information that ensures stable coordination. The results are discussed with respect to the proposal of Bingham and colleagues (e.g., Bingham GP. Ecol Psychol 16:45–53, 2004a; Wilson AD, Collins DR, Bingham GP. Exp Brain Res 165:351–361, 2005a) that the relevant information for rhythmic visual coordination is relative direction information.     

The stability of rhythmic movement coordination depends on relative speed: the Bingham model supported

Following many studies showing that the coupling in bimanual coordination can be perceptual, Bingham (Ecol Psychol in 16:45–53, 2001; 2004a, b) proposed a dynamical model of such movements. The model contains three key hypotheses: (1) Being able to produce stable coordinative movements is a function of the ability to perceive relative phase, (2) the information to perceive relative phase is relative direction of motion, and (3) the ability to resolve this information is conditioned by relative speed. The first two hypotheses have been well supported (Wilson and Bingham in Percept Psychophys 70:465–476, 2008; Wilson et al. in J Exp Psychol Hum 36:1508–1514, 2010a), but the third was not supported when tested by de Rugy et al. (Exp Brain Res 184:269–273, 2008) using a visual coordination task that required simultaneous control of both the amplitude and relative phase of movement. The purposes of the current study were to replicate this task with additional measures and to modify the original model to apply it to the new task. To do this, we conducted two experiments. First, we tested the ability to produce 180° visual coordination at different frequencies to determine frequencies suitable for testing in the de Rugy et al. task. Second, we tested the de Rugy et al. task but included additional measures that yielded results different from those reported by de Rugy et al. These results were used to elaborate the original model. First, one of the phase-driven oscillators was replaced with a harmonic oscillator, so the resulting coupling was unidirectional. This change resulted in the model producing less stable 180° coordination behavior beyond 1.5 Hz consistent with the results obtained in Experiment 1. Next, amplitude control and phase correction elements were added to the model. With these changes, the model reproduced behaviors observed in Experiment 2. The central finding was that the stability of rhythmic movement coordination does depend on relative speed and, thus, all three of the hypotheses contained in the original Bingham model are supported.     

Learning an environment–actor coordination skill: visuomotor transformation and coherency of perceptual structure

The coordination dynamics of learning were examined in a visuomotor tracking task. Participants produced rhythmic elbow flexion–extension motions to learn a visually defined 90° relative phase tracking pattern with an external sinusoidal signal. There were two visuomotor transformation groups, a correct feedback group and a mirrored feedback group with feedback representing the elbow’s motion transformed by 180°. In Experiment 1, the to-be-tracked signal and the participant’s motion signal were superimposed within a single window display. In Experiment 2, the to-be-tracked signal and participant’s signal were presented in separate windows. Before day 1 practice and 24 h after day 2 practice, participants attempted visually defined 0°, 45°, 90°, 135°, and 180° relative phase tracking patterns either with or without visual feedback of the arm’s motion. Before practice, only the 0° and 180° tracking patterns were stable. Practice led to a decrease in phase error toward the required 90° relative phase pattern with a corresponding increase in stability in both the experiments. No effect of visual transformation on performance emerged during practice in the single window task, but did emerge in the two window task. The one window training facilitated transfer to the four unpracticed relative phase patterns, whereas the two window training display only facilitated transfer performance to a single unpracticed relative phase pattern. These findings suggest that the perceptual structure determined the degree of learning and transfer and interacted with the visuomotor transformation. The present findings are discussed with reference to how the visual display constrains the coherency of independent signals with regard to learning and transfer and the role of perceptual discrimination processes linked to transfer.

Visual–spatial and anatomical constraints interact in a bimanual coordination task with transformed visual feedback

There is a debate in the literature about the influence of spatial and anatomical constraints on bimanual coordination dynamics. In the present experiment, participants swung hand-held pendulums about the wrist while attending to visual feedback about relative phase (superimposed phase plots of each pendulum) that was displayed on a screen. Participants were instructed to maintain in-phase or anti-phase coordination in the visual display. Visual–spatial and anatomical constraints were dissociated by introducing a phase shift in the visual display so that visual feedback differed from the movements being performed by the participants in 15° increments from −180° to +180°. Analysis of mean relative phase and its variability suggested that visual–spatial and anatomical constraints interact in bimanual coordination dynamics.     

Amplitude differences, spatial assimilation, and integrated feedback in bimanual coordination

The purpose of the experiment was to determine the influence of Lissajous feedback on 1:1 bimanual coordination patterns (0°, 90°, and 180° phase lags) when the movement amplitudes of the two limbs were different (30°, 60°). The present data supports the notion that the lead–lag relationship as well as amplitude assimilation observed in the literature can be partially attributed to the visual-perceptual factors present in the testing environment. When participants are provided integrated feedback in the form of Lissajous plots much of the lead–lag and amplitude assimilation effects were eliminated, and relative phase error and variability were also greatly reduced after only 3 min of practice under each condition.     

Transient visual field defects induced by transcranial magnetic stimulation over human occipital pole

Transient visual field defects (VFDs) and phosphenes were induced in normal volunteers by means of transcranial magnetic stimulation (TMS) using a circular magnetic coil of 12.5 cm diameter placed with its lower rim 2–4 cm above the inion in the midline. Subjects had to detect small, bright dots presented randomly for 14 ms in one of 60 locations on a computer screen resulting in a plot of the central 9° of the visual field. In 8 of 17 subjects, transient VFDs were inducible at peak magnetic field strenghts of 1.1–1.4 T. In the central 1–3°, detection of targets was impaired in both the upper and lower visual field, whereas at 4–9° large parts of only the lower visual field were affected with a sharp cut-off along the horizontal meridian. Targets at 1° in the lower field were affected with lower TMS intensities than corresponding locations in the upper or peripheral locations in the lower field. Detection of central targets was affected at more caudal stimulation sites than detection of peripheral targets. Phosphenes were elicitable in 14 of 17 subjects at clearly lower field strengths of 0.6–1.0 T. Many subjects perceived chromatophosphenes. From a discussion of the literature on patients with VFDs and the known topography of the human visual system, it is concluded that the transient VFDs at 1–3° are probably due to stimulation of both striate cortex (V1) and extrastriate areas (V2/V3), while VFDs in the lower visual field at eccentricities 4–9° are due to stimulation of V2/V3 but not V1. Received: 14 January 1997 / Accepted: 2 June 1997     

Head position modulates optokinetic nystagmus

Orientation and movement relies on both visual and vestibular information mapped in separate coordinate systems. Here, we examine how coordinate systems interact to guide eye movements of rabbits. We exposed rabbits to continuous horizontal optokinetic stimulation (HOKS) at 5°/s to evoke horizontal eye movements, while they were statically or dynamically roll-tilted about the longitudinal axis. During monocular or binocular HOKS, when the rabbit was roll-tilted 30° onto the side of the eye stimulated in the posterior → anterior (P → A) direction, slow phase eye velocity (SPEV) increased by 3.5–5°/s. When the rabbit was roll-tilted 30° onto the side of the eye stimulated in the A → P direction, SPEV decreased to ~2.5°/s. We also tested the effect of roll-tilt after prolonged optokinetic stimulation had induced a negative optokinetic afternystagmus (OKAN II). In this condition, the SPEV occurred in the dark, “open loop.” Modulation of SPEV of OKAN II depended on the direction of the nystagmus and was consistent with that observed during “closed loop” HOKS. Dynamic roll-tilt influenced SPEV evoked by HOKS in a similar way. The amplitude and the phase of SPEV depended on the frequency of vestibular oscillation and on HOKS velocity. We conclude that the change in the linear acceleration of the gravity vector with respect to the head during roll-tilt modulates the gain of SPEV depending on its direction. This modulation improves gaze stability at different image retinal slip velocities caused by head roll-tilt during centric or eccentric head movement.     

Visuomotor mental rotation of saccade direction

This investigation studied the latencies of saccadic eye movements that were directed away from a target by a variable angular distance, which was given by instruction. Such a movement presumably requires an intentional, visuomotor mental rotation of the saccade vector, resulting in prolonged reaction times. From a study on the control of directed hand movements, it has been hypothesized that all visuomotor and visual mental rotation tasks share a common processing stage. We tested this hypothesis with a saccade task in which subjects shifted their gaze either towards (0°, pro-saccade), or 30, 60, 90, 120, 150, or 180° (anti-saccade) away from a randomly cued position on an imaginary clock face. With four different cueing conditions, latencies increased monotonically with required gaze shift from 0–150°, thus exhibiting a mental rotation latency pattern. However, we also found anti-saccades faster than 150° gaze shift and slower rotation speeds with peripheral cues than with central cues. Together with the overall shallower latency increase compared with previous findings with mental rotation tasks, these results cast doubt on the notion of a common, central processing mechanism for the different types of tasks. Received: 11 August 1998 / Accepted: 9 February 1999     

Learning a coordinated rhythmic movement with task-appropriate coordination feedback

A common perception–action learning task is to teach participants to produce a novel coordinated rhythmic movement, e.g. 90° mean relative phase. As a general rule, people cannot produce these novel movements stably without training. This is because they are extremely poor at discriminating the perceptual information required to coordinate and control the movement, which means people require additional (augmented) feedback to learn the novel task. Extant methods (e.g. visual metronomes, Lissajous figures) work, but all involve transforming the perceptual information about the task and thus altering the perception–action task dynamic being studied. We describe and test a new method for providing online augmented coordination feedback using a neutral colour cue. This does not alter the perceptual information or the overall task dynamic, and an experiment confirms that (a) feedback is required for learning a novel coordination and (b) the new feedback method provides the necessary assistance. This task-appropriate augmented feedback therefore allows us to study the process of learning while preserving the perceptual information that constitutes a key part of the task dynamic being studied. This method is inspired by and supports a fully perception–action approach to coordinated rhythmic movement.     

Microstimulation of V1 delays visually guided saccades: a parametric evaluation of delay fields

Electrical microstimulation of macaque striate cortex (area V1) delays the execution of saccadic eye movements made to a visual target placed in the receptive field of the stimulated neurons. The region of visual space within which saccades are delayed is called a delay field. We examined the effects of changing the parameters of stimulation and target size on the size of a delay field. Rhesus monkeys were required to generate a saccadic eye movement to a punctate and white visual target presented within or outside the receptive field of the neurons under study. On 50% of trials, a train of stimulation consisting of 0.2-ms anode-first pulses was delivered to the neurons before the onset of the visual target. Stimulations were performed in the operculum at 0.9–2.0 mm below the cortical surface. It was found that increases in current (50–100 μA), pulse frequency (100–300 Hz), or train duration (75–300 ms) increased the size of a delay field and increases in target size (0.1°–0.2° of visual angle) decreased the size of a delay field. Delay fields varied in size between 0.1 and 0.6° of visual angle. These results are related to the properties of phosphenes induced by electrical stimulation of V1 in humans and compared to the interference effects observed following transcranial magnetic stimulation of human V1.     

Task-related power and coherence changes in neuromagnetic activity during visuomotor coordination

We analyzed a set of full-head (66 channels, CTF Inc.) magnetoencephalography (MEG) data recorded when 5 subjects performed rhythmic right index-finger flexion and extension movements on the beat (synchronization) or off the beat (syncopation) with a visual metronome at 1 Hz. Neuromagnetic activities in the alpha (8–14 Hz), beta (15–30 Hz) and gamma (30–50 Hz) ranges were shown to correlate with different aspects of the task. Specifically, we found that, compared with the control condition in which subjects only looked at the visual metronome without making any movement, all the movement conditions were accompanied by a decrease of power in the alpha range (8–14 Hz) in sensorimotor channels of both hemispheres, and an increase of coherence among a subset of these channels. The same comparison showed that power changes in the beta range differentiate task conditions by exhibiting power increases for synchronization and power decreases for syncopation. Changes in the gamma range power were found to be related to the kinematics of movement trajectories (flexion versus extension). These results suggest that three important cortical oscillations play different functional roles in a visuomotor timing task. Electronic Publication     

Functional importance of α-activity in the visual cortex during recognition of images and movement

Twenty-seven studies were carried out on the recognition of the shapes of geometrical figures of different sizes by healthy adults, on the recognition of the direction of movement of a light spot within the field of vision, and of visual illusions produced by rhythmic visual stimulation. Tachystoscopic presentation of figures and the onset of movement were synchronized with different phases of the EEG α-rhythm in the occipital region. In controls, stimuli were presented without a shift in the α-rhythm. Recognition improved significantly when small figures were presented at relatively late phases of the α-wave and when large figures (up to 9°) were presented at relatively early phases. Recognition of the side and direction of apparent movement (in the left or right halves of the visual field and centrifugal or centripetal) depended on the phase of the α-wave only for nonuniform (accelerating or decelerating, depending on direction) movement, allowing for the cortical magnification factor. Centrifugal movements in experiments were recognized better than in controls, while centripetal movements were recognized worse, and elicited a relatively long-latency movement response. Diffuse rhythmic light stimulation at the α-rhythm frequency produced the illusory percept of a ring or circle in 11 of 12 subjects. The optimal stimulation frequency for this was tightly connected with the dominant α-rhythm frequency, with a correlation coefficient of 0.86. The link between these effects and the propagation of the wave process through the visual cortex, as reflected by the EEG α-rhythm, is discussed. The data support the hypothesis of Pitts and McCulloch [29], which proposes scanning of the visual cortex by a wave process operating at the frequency of the α-rhythm, which reads information from the visual cortex. Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, 5A Butlerov Street, 117865 Moscow, Russia. Translated from Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 82, No. 10-11, pp. 20–33, October–November, 1996.     

Visuomotor mental rotation: the reaction time advantage for anti-pointing is not influenced by perceptual experience with the cardinal axes

In the visuomotor mental rotation (VMR) paradigm, participants execute a center-out reaching movement to a location that deviates from a visual cue by a predetermined instruction angle. Previous work has demonstrated a linear increase in reaction time (RT) as a function of the amplitude of the instruction angle (Georgopoulos and Massey in Exp Brain Res 65:361–370, 1987). In contrast, we recently reported a RT advantage for an instruction angle of 180° relative to a 90° angle (Neely and Heath in Neurosci Lett 463:194–198, 2009). It is possible, however, that perceptual expertise with the cardinal axes, which are perceptually familiar reference frames, influenced the results of our previous investigation. To address this issue, we employed a VMR paradigm identical to that of our previous work, with the exception that the stimulus array was shifted 45° from the horizontal and vertical meridians. Our results demonstrated that RTs were fastest and least variable when the instruction angle was 0°, followed by 180°, which in turn, was faster than 90°. Such findings establish that the RT advantage for the 180° instruction angle is not influenced by perceptual expertise with the cardinal axes. Moreover, the present results provide convergent evidence that RT is not determined by the angle of rotation; instead, they indicate that response latencies reflect computational differences in the complexity of response remapping.     

Concurrent adaptation to four different visual rotations

The human sensorimotor system can concurrently adapt to two different distortions without interference when the distortions are cued by different contexts. We investigated whether this holds with four distortions as well. Subjects were exposed to an interlaced sequence of +30°, −30°, +60°, and −60° visuomotor rotations as the adaptation phase, cued by combinations of workspace location and by the arm used. Adaptation phase was followed by two episodes in each condition without any distortion testing the aftereffects. Results showed that the error at the onset of adaptation gradually decreased during adaptation to all four distortions without any sign of interference between the conditions. Furthermore, aftereffects of adaptation to ±30° rotation were significantly greater than of adaptation to ±60° rotation. We conclude that the human sensorimotor system is able to concurrently adapt to four different visual distortions when they are cued by different contexts. However, the results of aftereffects are ambiguous: Recalibration could be based on at least four parallel modules.     

Look-ahead fixations: anticipatory eye movements in natural tasks

During performance of natural tasks subjects sometimes fixate objects that are manipulated several seconds later. Such early looks are known as “look-ahead fixations” (Pelz and Canosa in Vision Res 41(25–26):3587–3596, 2001). To date, little is known about their function. To investigate the possible role of these fixations, we measured fixation patterns in a model-building task. Subjects assembled models in two sequences where reaching and grasping were interrupted in one sequence by an additional action. Results show look-ahead fixations prior to 20% of the reaching and grasping movements, occurring on average 3 s before the reach. Their frequency was influenced by task sequence, suggesting that they are purposeful and have a role in task planning. To see if look-aheads influenced the subsequent eye movement during the reach, we measured eye-hand latencies and found they increased by 122 ms following a look-ahead to the target. The initial saccades to the target that accompanied a reach were also more accurate following a look-ahead. These results demonstrate that look-aheads influence subsequent visuo-motor coordination, and imply that visual information on the temporal and spatial structure of the scene was retained across intervening fixations and influenced subsequent movement programming. Additionally, head movements that accompanied look-aheads were significantly smaller in amplitude (by 10°) than those that accompanied reaches to the same locations, supporting previous evidence that head movements play a role in the control of hand movements. This study provides evidence of the anticipatory use of gaze in acquiring information about objects for future manipulation. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Stability of rhythmic visuo-motor tracking does not depend on relative velocity

It is well established that the in-phase pattern of bimanual coordination (i.e. a relative phase of 0°) is more stable than the antiphase pattern (i.e., a relative phase of 180°), and that a spontaneous transition from antiphase to in-phase typically occurs as the movement frequency is gradually increased. On the basis of results from relative phase perception experiments, Bingham (Proceedings of the 23rd annual conference of the cognitive science society. Laurence Erlbaum Associates, Mahwah, pp 75–79, 2001; Ecol Psychol 16:45–53, 2004; Advances in psychology 135: time-to-contact. Elsevier, Amsterdam, pp 421–442, 2004) proposed a dynamical model that consists of two phase driven oscillators coupled via the perceived relative phase, the resolution of which is determined by relative velocity. In the present study, we specifically test behavioral predictions from this last assumption during a unimanual visuo-motor tracking task. Different conditions of amplitudes and frequencies were designed to manipulate selectively relative phase and relative velocity. While the known effect of phase and frequency were observed, relative phase variability was not affected by the different conditions of relative velocity. As such, Bingham’s model assumption that instability in relative phase coordination is brought about by relative velocity that affects the resolution of the perceived relative phase has been invalidated for the case of rhythmic unimanual visuo-motor tracking. Although this does not rule out the view that relative phase production is constrained by relative phase perception, the mechanism that would be responsible for this phenomenon still has to be established.     

Task-dependent mixtures of coordinate systems in visuomotor transformations

In two experiments the involvement of relative and fixed coordinate systems in visuomotor transformations was examined. The experimental task required the successive performance of two movements in each trial, which had to “correspond” to different visual stimuli. One kind of visual display indicated target positions by way of different horizontal positions of a vertical line on a monitor (position mode), while the other indicated movement amplitudes by way of different lengths of a horizontal line (amplitude mode). Formal analysis of variances and covariances of successive individual movements led to the conclusion that in the position mode visuomotor transformations were based on a mixture of relative and fixed coordinate systems, while in the amplitude mode only a relative coordinate system was involved. Thus, visuomotor transformations can be characterized as mixtures of different coordinate systems, and their respective weights in the mixtures are task-dependent. Received: 18 March 1997 / Accepted: 25 September 1997     

Visuomotor adaptation and proprioceptive recalibration in older adults

Previous studies have shown that both young and older subjects adapt their reaches in response to a visuomotor distortion. It has been suggested that one’s continued ability to adapt to a visuomotor distortion with advancing age is due to the preservation of implicit learning mechanisms, where implicit learning mechanisms include processes that realign sensory inputs (i.e. shift one’s felt hand position to match the visual representation). The present study examined this proposal by determining if changes in sense of felt hand position (i.e. proprioceptive recalibration) follow visuomotor adaptation in older subjects. As well, we examined the influence of age on proprioceptive recalibration by comparing young and older subjects’ estimates of the position at which they felt their hand was aligned with a visual reference marker before and after aiming with a misaligned cursor that was gradually rotated 30° clockwise of the actual hand location. On estimation trials, subjects moved their hand along a robot-generated constrained pathway. At the end of the movement, a reference marker appeared and subjects indicated if their hand was left or right of the marker. Results indicated that all subjects adapted their reaches at a similar rate and to the same extent across the reaching trials. More importantly, we found that both young and older subjects recalibrated proprioception, such that they felt their hand was aligned with a reference marker when it was approximately 6° more left (or counterclockwise) of the marker following reaches with a rotated cursor. The leftward shift in both young and older subjects’ estimates was in the same direction and a third of the extent of adapted movement. Given that the changes in the estimate of felt hand position were only a fraction of the changes observed in the reaching movements, it is unlikely that sensory recalibration was the only source driving changes in reaches. Thus, we propose that proprioceptive recalibration combines with adapted sensorimotor mappings to produce changes in reaching movements. From the results of the present study, it is clear that changes in both sensory and motor systems are possible in older adults and could contribute to the preserved visuomotor adaptation.     

Visuomotor memory is independent of conscious awareness of target features

A recent study by our group showed that the scaling of reach trajectories to target size is independent of conscious visual awareness of that intrinsic target property (Binsted et al. in Proc Natl Acad Sci USA 104:12669–12672, 2007). The present investigation sought to extend previous work and determine whether unconscious target information represents a temporally durable or evanescent visuomotor characteristic. To accomplish that objective, we employed Di Lollo et al’s (J Exp Psychol Gen 129:481–507, 2000) object substitution masking paradigm and asked participants to complete verbal reports and reaching responses to different sized (1.5, 2.5, 3.5, 4.5, 5.5 cm) targets under masked and non-masked target conditions. To determine whether visuomotor networks retain unconscious target information, reaching trials were cued concurrent with target presentation or 1,000 or 2,000 ms after target presentation. For the perceptual trials, participants readily identified the size of non-masked trials but demonstrated only chance success identifying target size during masked trials. Interestingly, however, reaches directed to non-masked and masked targets exhibited comparable and robust scaling with target size; that is, lawful speed-accuracy relations related to movement planning and execution times were observed regardless of whether participants were aware (i.e., non-masked trials) or unaware (i.e., masked trials) of target size. What is more, the length of the visual delay period used here did not differentially influence the scaling of reach trajectories. These results indicate that a conscious visual percept is not necessary to support motor output and that unconscious visual information persists in visuomotor networks to support the kinematic parameterization of action.

Dual transplantation of human neural stem cells into cervical and lumbar cord ameliorates motor neuron disease in SOD1 transgenic rats

During gain adaptation, participants must learn to adapt to novel visuo-motor mappings in which the movement amplitudes they produce do not match the visual feedback they receive. The aim of the present study was to investigate the neural substrates of gain adaptation by examining its possible disruption following left hemisphere stroke. Thirteen chronic left hemisphere stroke patients and five healthy right-handed control subjects completed three experimental phases involving reaching with the left hand, which was the less-affected hand in patients. First, participants reached without visual feedback to six different target locations (baseline phase). Next, in the adaptation phase, participants executed movements to one target under conditions in which the perceived movement distance was 70% of the produced movement distance. Last, in order to test the generalization of this new visuomotor mapping, participants made movements without visual feedback to untrained target locations (generalization phase). Significant between-patient differences were observed during adaptation. Lesion analyses indicated that these between-patient differences were predicted by the amount of damage to the supramarginal gyrus (Brodmann area 40). In addition, patients performed more poorly than controls in the generalization phase, suggesting that different processes are involved in adaptation and generalization periods.