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At least 667 records · Page 37Linked to original sources

PubMed2001

Recognition of self-generated actions from kinematic displays of drawing.

Five experiments addressed the question of whether individuals can distinguish between self-generated and other-generated actions when seeing their visual effects. Each experiment consisted of a recording session in which participants drew familiar and unfamiliar characters without receiving visual feedback and a recognition session in which they provided self-or-other judgments (SOJs) to indicate whether a kinematic display reproduced the visual effects of their own actions. The main results were that self-generated and other-generated drawing can be distinguished, that the familiarity of character shapes does not influence the accuracy of SOJs, and that velocity information is crucial for the identification of self-generated drawing. The ability to determine authorship from kinematic displays of drawing provides evidence for the contribution of action-planning structures to perception.

Adult↗

PubMed1999

Haltere-mediated equilibrium reflexes of the fruit fly, Drosophila melanogaster.

Flies display a sophisticated suite of aerial behaviours that require rapid sensory-motor processing. Like all insects, flight control in flies is mediated in part by motion-sensitive visual interneurons that project to steering motor circuitry within the thorax. Flies, however, possess a unique flight control equilibrium sense that is encoded by mechanoreceptors at the base of the halteres, small dumb-bell-shaped organs derived through evolutionary transformation of the hind wings. To study the input of the haltere system onto the flight control system, I constructed a mechanically oscillating flight arena consisting of a cylindrical array of light-emitting diodes that generated the moving image of a 30 degrees vertical stripe. The arena provided closed-loop visual feedback to elicit fixation behaviour, an orientation response in which flies maintain the position of the stripe in the front portion of their visual field by actively adjusting their wing kinematics. While flies orientate towards the stripe, the entire arena was swung back and forth while an optoelectronic device recorded the compensatory changes in wing stroke amplitude and frequency. In order to reduce the background changes in stroke kinematics resulting from the animal's closed-loop visual fixation behaviour, the responses to eight identical mechanical rotations were averaged in each trial. The results indicate that flies possess a robust equilibrium reflex in which angular rotations of the body elicit compensatory changes in both the amplitude and stroke frequency of the wings. The results of uni- and bilateral ablation experiments demonstrate that the halteres are required for these stability reflexes. The results also confirm that halteres encode angular velocity of the body by detecting the Coriolis forces that result from the linear motion of the haltere within the rotating frame of reference of the fly's thorax. By rotating the flight arena at different orientations, it was possible to construct a complete directional tuning map of the haltere-mediated reflexes. The directional tuning of the reflex is quite linear such that the kinematic responses vary as simple trigonometric functions of stimulus orientation. The reflexes function primarily to stabilize pitch and yaw within the horizontal plane.

Animals↗

PubMed1986

Biofeedback-assisted control of peripheral skin temperature: a methodological study.

To maximize the production and detection of training effects in biofeedback-assisted control of peripheral skin temperature, this study incorporated these methodological features: differential feedback between dominant and nondominant hands, monetary incentives, within-subjects manipulation of training direction and multiple-training sessions, graphic-based visual feedback, and no-feedback self-control periods. Eight male subjects participated in eight sessions each consisting of adaptation (22 min.), bidirectional self-control (10 min.), and bidirectional feedback training (35 min.). Mean differential temperature changes were significantly different for increase and decrease conditions, but the magnitude of control did not change over sessions. Differential feedback control was of small magnitude and tended to be accomplished by decreasing both hands at different rates; self-control did not develop during the course of training. This methodology did not produce large-magnitude feedback, or self-control, but differential feedback is recommended for further study as an experimental paradigm.

Adult↗

PubMed2006

Abrupt, but not gradual visuomotor distortion facilitates adaptation in children with developmental coordination disorder.

A previous experiment investigating visuomotor adaptation in typically developing children and children with Developmental Coordination Disorder (DCD) suggested poor adaptation to an abruptly induced visuomotor perturbation. In the current study, using a similar center-out drawing task, but administering either an abrupt or a gradual perturbation, and twice as many adaptation trials, we show that typically developing children are well able to successfully update an existing internal model in response to a 60 degrees rotation of the visual feedback, independent of the perturbation condition. Children with DCD, however, updated their internal map more effectively during exposure to an abrupt visuomotor perturbation than to a gradual one. This may suggest that the adaptation process in children with DCD responds differently to small vs. large steps of visuomotor discrepancies. Given the known role of the cerebellum in providing an error signal necessary for updating the internal model in response to a gradual visuomotor distortion, the results of our study add to the growing body of evidence implicating compromised cerebellar function in DCD.

Attention↗

PubMed1998

Motion sickness and development of synergy within the spatial orientation system. A hypothetical unifying concept.

Adaptation to research paradigms such as rotating rooms and optical alteration of visual feedback during movement results in development of perceptual-motor programs that provide the reflexive assistance that is necessary to skilled control of movement and balance. The discomfort and stomach awareness that occur during the adaptation process has been attributed to conflicting sensory information about the state of motion. Vestibular signals depend on the kinematics of head movements irrespective of the presence or absence of signals from other senses. We propose that sensory conflict when vestibular signals are at least one component of the conflict are innately disturbing and unpleasant. This innate reaction is part of a continuum that operates early in life to prevent development of inefficient perceptual-motor programs. This reaction operates irrespective of and in addition to reward and punishment from parental guidance or goal attainment to yield efficient control of whole body movement in the operating environment of the individual. The same mechanism is involved in adapting the spatial orientation system to strange environments. This conceptual model "explains" why motion sickness is associated with adaptation to novel environments and is in general consistent with motion sickness literature.

Adaptation, Physiological↗

PubMed2001

Control strategies when intercepting slowly moving targets.

In 3 experiments, the authors investigated and described how individuals control manual interceptive movements to slowly moving targets. Participants (N = 8 in each experiment) used a computer mouse and a graphics tablet assembly to manually intercept targets moving across a computer screen toward a marked target zone. They moved the cursor so that it would arrive in the target zone simultaneously with the target. In Experiment 1, there was a range of target velocities, including some very slow targets. In Experiment 2, there were 2 movement distance conditions. Participants moved the cursor either the same distance as the target or twice as far. For both experiments, hand speed was found to be related to target speed, even for the very slowly moving targets and when the target-to-cursor distance ratios were altered, suggesting that participants may have used a strategy similar to tracking. To test that notion, in Experiment 3, the authors added a tracking task in which the participants tracked the target cursor into the target zone. Longer time was spent planning the interception movements; however, there was a longer time in deceleration for the tracking movements, suggesting that more visually guided trajectory updates were made in that condition. Thus, although participants scaled their interception movements to the cursor speed, they were using a different strategy than they used in tracking. It is proposed that during target interception, anticipatory mechanisms are used rather than the visual feedback mechanism used when tracking and when pointing to stationary targets.

Adult↗

PubMed2002

The influence of visual landscape on the free flight behavior of the fruit fly Drosophila melanogaster.

To study the visual cues that control steering behavior in the fruit fly Drosophila melanogaster, we reconstructed three-dimensional trajectories from images taken by stereo infrared video cameras during free flight within structured visual landscapes. Flies move through their environment using a series of straight flight segments separated by rapid turns, termed saccades, during which the fly alters course by approximately 90 degrees in less than 100 ms. Altering the amount of background visual contrast caused significant changes in the fly's translational velocity and saccade frequency. Between saccades, asymmetries in the estimates of optic flow induce gradual turns away from the side experiencing a greater motion stimulus, a behavior opposite to that predicted by a flight control model based upon optomotor equilibrium. To determine which features of visual motion trigger saccades, we reconstructed the visual environment from the fly's perspective for each position in the flight trajectory. From these reconstructions, we modeled the fly's estimation of optic flow on the basis of a two-dimensional array of Hassenstein-Reichardt elementary motion detectors and, through spatial summation, the large-field motion stimuli experienced by the fly during the course of its flight. Event-triggered averages of the large-field motion preceding each saccade suggest that image expansion is the signal that triggers each saccade. The asymmetry in output of the local motion detector array prior to each saccade influences the direction (left versus right) but not the magnitude of the rapid turn. Once initiated, visual feedback does not appear to influence saccade kinematics further. The total expansion experienced before a saccade was similar for flight within both uniform and visually textured backgrounds. In summary, our data suggest that complex behavioral patterns seen during free flight emerge from interactions between the flight control system and the visual environment.

Animals↗

PubMed1996

Generalization to local remappings of the visuomotor coordinate transformation.

During visually guided movement, visual representations of target location must be transformed into coordinates appropriate for movement. To investigate the representation and plasticity of the visuomotor coordinate transformation, we examined the changes in pointing behavior after local visuomotor remappings. The visual feedback of finger position was limited to one or two locations in the workspace, at which a discrepancy was introduced between the actual and visually perceived finger position. These remappings induced changes in pointing, which were largest near the locus of remapping and decreased away from it. This pattern of spatial generalization highly constrains models of the computation of the visuomotor transformation in the CNS. A simple model, in which the transformation is computed via the population activity of a set of units with large sensory receptive fields, is shown to capture the observed pattern.

Adolescent↗

PubMed2006

Functional activation in parieto-premotor and visual areas dependent on congruency between hand movement and visual stimuli during motor-visual priming.

Electrophysiological studies in monkeys and neuroimaging studies of humans have shown that action execution and action observation share neural processing sites traditionally thought to be responsible for motor execution alone. This experiment investigates a behavioral phenomenon in which a visual discrimination task is influenced by concurrent motor performance. Functional magnetic resonance imaging (fMRI) was used to determine whether this discrimination task uses components of the motor system. Participants viewed and responded to an animated hand while performing either congruent or incongruent right hand actions; the visual presentation was either a sequence showing a hand opening and closing, or randomly ordered frames from this series. The participant responded to onscreen target hand postures on a left footpedal. Previous behavioral results have shown a reaction time advantage on this discrimination task when performing congruent compared to incongruent hand actions, but only for sequential visual presentation. Left superior parietal lobule (SPL) and dorsal premotor cortex were more strongly activated when visual series and hand action did not match, as were dorsal premotor cortex and primary visual cortex. These results suggest that mismatches between performed action and visual feedback produce an inaccurate neural representation of limb state, which we suggest causes the contralateral SPL activation. This representation could not be used in the visual discrimination task, requiring increased reliance on direct visual inputs in order to perform the discrimination task accurately.

Adolescent↗

PubMed2003

Multisensory integration during motor planning.

When planning goal-directed reaches, subjects must estimate the position of the arm by integrating visual and proprioceptive signals from the sensory periphery. These integrated position estimates are required at two stages of motor planning: first to determine the desired movement vector, and second to transform the movement vector into a joint-based motor command. We quantified the contributions of each sensory modality to the position estimate formed at each planning stage. Subjects made reaches in a virtual reality environment in which vision and proprioception were dissociated by shifting the location of visual feedback. The relative weighting of vision and proprioception at each stage was then determined using computational models of feedforward motor control. We found that the position estimate used for movement vector planning relies mostly on visual input, whereas the estimate used to compute the joint-based motor command relies more on proprioceptive signals. This suggests that when estimating the position of the arm, the brain selects different combinations of sensory input based on the computation in which the resulting estimate will be used.

Adult↗

PubMedDate not supplied

Delayed intermodal contingency affects young children's recognition of their current self.

This study investigated whether 2-, 3-, and 4-year-olds use their video feedback as a reflection of their current state, even when their feedback was presented with a short temporal delay. In Experiment 1, the effects of 1- and 2-s delayed feedback were examined on an analog of the mark test. In the case of live and 1-s delayed feedback, 3-year-olds passed the test; however, they failed in the case of 2-s delayed feedback. Experiment 2 examined the effect of prior experience of delayed contingency and explorative behavior. The results showed a significant effect of prior experience. These results suggest that detection of visual-proprioceptive contingency contributes to recognition of visual feedback as one's current self.

Association Learning↗

PubMed1975

Feedback of true heart rate during exposure in vivo.

Ten women with specific chronic animal phobias were treated by graded exposure in vivo in two to four two-hour treatment sessions. Sessions were divided into four balanced half-hour epochs, half with visual feedback of true heart rate plus instructions to lower heart rate during approach to phobic stimulus. All patients improved significantly from the start to end of sessions on heart rate and on subjective anxiety. Feedback of heart rate plus instructions to lower it substantially reduced heart rate during epochs of feedback, compared to non-feedback epochs without instructions, but this effect did not generalize to skin conductance or to subjective anxiety in our short-term experiment.

Adult↗

PubMed2006

Integrity of lateral and feedbackward connections in visual processing in children with pervasive developmental disorder.

Enhanced visual detail processing in subjects with pervasive developmental disorder (PDD) has been related to impairments in feature integration. The functional integrity of two types of neuronal connections involved in visual feature integration, namely horizontal and feedbackward connections, were tested. Sixteen children with PDD and 17 age- and IQ-matched control children (mean age 13.3 years) were included. In a texture segregation task the difference in ERP response to homogeneous and checkered visual stimuli was determined. Additionally, in a contour integration task subjects had to point out a contour consisting of colinearly aligned Gabor signals in backgrounds increasing in noise. Children with PDD showed a normal performance on the contour integration task, suggesting that neurons in the primary visual cortex of children with PDD can effectively integrate the activity of local detectors that process different aspects of the same object information by making use of long-range lateral connections. The amplitude of ERP activity related to texture segregation was also not different between the PDD and control groups, indicating functional visual feedback mechanisms between V1 and higher order areas in subjects with PDD. However, a difference in latency of texture-segmentation related activity between the groups was noted. This effect did not reach significance, which could be due to the small N of the study. Therefore, the data need replication in a study with larger samples before more definitive conclusions can be drawn.

Adolescent↗

PubMed1978

Visual-vestibular interaction in the control of eye movement.

Three experimental conditions have been used to investigate the extent to which inappropriate reflex eye movements of vestibular origin can be suppressed by visual feedback. First, the ability to read digits in a display which moved with the head was assessed during angular oscillation about the yaw and pitch axes of the body. Performance decrement was observed at frequencies above 0.2 Hz in pitch and 1.0 Hz in yaw, being greater at higher stimulus velocity levels. A second experiment revealed that the performance decrement was associated with eye movements relative to the head, which increased with the frequency of stimulation. Finally, the response of the pursuit reflex was investigated under similar experimental conditions. The results indicated that the breakdown in the pursuit reflex and in the suppression of the vestibulo-ocular reflex occurred over the same frequency band, implying the similarity of the mechanisms responsible for suppression and pursuit.

Aerospace Medicine↗

PubMed1994

A spatiotemporal dipole model of the stimulus preceding negativity (SPN) prior to feedback stimuli.

Ten subjects performed a time production task, in which they were instructed to press a button four seconds after the presentation of an auditory stimulus. Two seconds after the button press they received either auditory or visual feedback on the temporal accuracy of their response. In such a paradigm negative slow brain potentials can be recorded preceding the response (Movement Preceding Negativity, MPN) as well as preceding the feedback stimulus (Stimulus Preceding Negativity, SPN). Spatiotemporal dipole modelling is used to gain insight in the possible generators of MPN and SPN. From the models it follows that the MPN can be described by one contralateral radial dipole and a bilateral pair of tangential dipoles. All three dipoles are located near central electrode positions, so the generators of the MPN probably reside within the motor cortex. The SPN is modelled by a bilateral frontotemporal pair of dipoles, hypothetically representing activation of the Insulae Reili. The insular cortex is involved in the processing of affective-motivational input, such as carried by the feedback in the present paradigm. However, processing of the information content of the feedback stimulus might by itself also activate the frontal cortex. Both the response and the feedback stimulus are followed by a positive peak, which can be described by the same deep posterior dipole. Both peaks probably represent a P3, which is related to context updating.

Adult↗

PubMed2004

The role of vision in spatial representation.

A complex link exists between vision and unilateral spatial neglect (USN). Firstly, USN is not a perceptual deficit, secondly, USN is not necessarily accompanied by a visual deficit and finally, USN can be observed in non-visual modalities as well as in mental spatial imagery. This apparent supramodality of USN stands in sharp contrast to the fact that neglect signs are often more severe and more durable in the visual than in other sensory modalities (Chokron et al., 2002). The influence of vision on spatial representation has rarely been studied. In the present study we assessed six right brain-damaged patients suffering from left USN on two tasks involving spatial representations: a clock-drawing task and a drawing from memory task in two experimental conditions, with and without visual control. We confirm that even in mental imagery, the absence of visual feedback may decrease and even suppress left neglect signs (Bartolomeo and Chokron, 2001b; 2002). Since vision is largely involved in the orientation of attention in space, suppressing visual control could reduce the magnetic attraction towards the right ipsilesional hemispace and in this way could allow a re-orientation of attention towards the left neglected hemispace. We discuss the theoretical and therapeutic implications of these findings.

Adult↗

PubMed1995

The locus of visual-motor learning at the task or manipulator level: implications from intermanual transfer.

To assess the functional locus of visual-motor learning, the computational concepts of "task level" programming (determination of the trajectory of a hand during arm reaching in the Cartesian coordinates) and "manipulator level" programming (determination of the joint coordinates) was adopted. Because the former is likely to be hand nonspecific and the latter is hand specific, it is assumed that learning at the task level should be transferred to the unpracticed hand, whereas that at the manipulator level it should not. Under this assumption, the paradigm of intermanual transfer was used in an aiming task under rotated visual feedback. Nearly 100% intermanual transfer from the practiced hand to the unpracticed hand in the performance time of aiming was found, concluding that the locus of visual-motor learning should be at the task level rather than at the manipulator level.

Adolescent↗

PubMed1988

Ocular torsion: sensorimotor principles.

Eye movements are basically limited to two degrees of freedom, as described by Donders' and Listing's laws. Complex patterns of innervation maintain the geometric constancy of the retinal meridians, presumably via visual feedback acting through orientation-specific neurons in the cortex. Interactions between torsional and vertical movements of the eyes can be demonstrated by stimulating ocular torsion and detecting secondary vertical deviations. Geometric considerations show that significant peripheral disparities occur with convergence and eye movements, dictating large Panum's fusional areas in the periphery. Good visual acuity in man must thus be limited to the fovea, but the large peripheral Panum's fusional areas allow sensory cyclofusion of up to 8 degrees. In addition, motor cyclofusion occurs in the presence of large-field stimuli, further helping to minimize problems from torsional diplopia both in normal individuals and in patients with ocular motor pareses.

Convergence, Ocular↗