School of Psychology, University of Sydney, Sydney, NSW, Australia. email@example.com
Vibration of the dorsolateral neck stimulates proprioceptors that are normally active during head movement; this induces a visual illusion of contralateral motion and displacement of a stationary target seen against a homogenous background. The spatial constancy explanation of the illusion argues that it occurs because information about head movement is necessary for accurate egocentric localization of visual objects. Accurate egocentric localization, in turn, is necessary for the success of object-directed motor action, but previous studies failed to find evidence that vibration affects pointing toward visual targets in a normally illuminated, structured field. Our goal was to provide this evidence. Vibration lasting 12 s was applied to either side of the neck while observers (N = 11) pointed at the visual target with an unseen hand. Vibration of the right side of dorsal neck in the illuminated visual field induced a 26-mm lateral bias in pointing responses in comparison to the vibration of the left side. We conclude that the mechanism that takes into account neck proprioceptive signals also operates in full cues. The pointing bias in full cues generally co-occurred with reported stationariness of the visual target, suggesting a conflict between cues used in perception of body-centric position used to guide action, which include neck proprioception, and those used in perception of motion, for which object-relative retinal information is sufficient.
Strength in numbers: combining neck vibration and prism adaptation produces additive therapeutic effects in unilateral neglect.
Department Neuropsychology, University of Freiburg, Freiburg, Germany. firstname.lastname@example.org
Unilateral neglect is a multifaceted disorder. Many authors have, for this reason, speculated that the best treatment for neglect will involve combinations of different therapeutic techniques. Two well-known interventions, neck vibration (NV) and prism adaptation (PA), have often been considered to be among the most effective treatments for neglect. Here, two experiments were performed to explore possible additive benefits when these interventions are used in combination to treat chronic neglect. Both experimental groups received NV for 20 minutes, while the second group received simultaneous PA. The effects of treatment were measured with a time-restricted and feedback-based visual search task, which has previously been found to abolish the beneficial effects of PA, and with standard neglect tests. Baseline and intervention measures were performed on separate days. Findings for both groups indicated improved visual search following intervention, but the patients that underwent the combined intervention (NVPA) showed clear improvements on visual search paper and pencil neglect tests unlike the NV-only group. Overall, our results suggest that PA strengthens the effects of NV and that feedback-based tasks do not abolish the beneficial effects of PA, when NV is applied simultaneously. The results support the view that the most effective treatment for neglect will involve the combination of different treatments.
Other papers by authors:
PLoS One. 2012 ;7 (9):e45438 23029010
Faculty of Health Sciences, University of Sydney, Sydney, Australia ; School of Psychology, University of Sydney, Sydney, Australia.
INTRODUCTION: While the directionality of tactile motion processing has been studied extensively, tactile speed processing and its relationship to direction is little-researched and poorly understood. We investigated this relationship in humans using the 'tactile speed aftereffect'(tSAE), in which the speed of motion appears slower following prolonged exposure to a moving surface. METHOD: We used psychophysical methods to test whether the tSAE is direction sensitive. After adapting to a ridged moving surface with one hand, participants compared the speed of test stimuli on the adapted and unadapted hands. We varied the direction of the adapting stimulus relative to the test stimulus. RESULTS: Perceived speed of the surface moving at 81 mms(-1) was reduced by about 30% regardless of the direction of the adapting stimulus (when adapted in the same direction, Mean reduction = 23 mms(-1), SD = 11; with opposite direction, Mean reduction = 26 mms(-1), SD = 9). In addition to a large reduction in perceived speed due to adaptation, we also report that this effect is not direction sensitive. CONCLUSIONS: Tactile motion is susceptible to speed adaptation. This result complements previous reports of reliable direction aftereffects when using a dynamic test stimulus as together they describe how perception of a moving stimulus in touch depends on the immediate history of stimulation. Given that the tSAE is not direction sensitive, we argue that peripheral adaptation does not explain it, because primary afferents are direction sensitive with friction-creating stimuli like ours (thus motion in their preferred direction should result in greater adaptation, and if perceived speed were critically dependent on these afferents' response intensity, the tSAE should be direction sensitive). The adaptation that reduces perceived speed therefore seems to be of central origin.
Dev Med Child Neurol. 2012 Nov 26;: 23181910
A systematic review of risk factors for cerebral palsy in children born at term in developed countries.
Paediatrics and Child Health, School of Medicine, University of Sydney, Sydney; Cerebral Palsy Alliance Research Institute, Darlinghurst; School of Medicine, University of Notre Dame Australia, Darlinghurst; Sydney Adventist Hospital Campus, University of Sydney, Wahroonga; Grace Centre for Newborn Care, Sydney Children's Hospital Network, Westmead; Centre for Child Health Research, University of Western Australia at the Telethon Institute for Child Health Research, Perth, Australia.
Aim The aim of this study was to conduct a systematic review in order to identify the risk factors for cerebral palsy (CP) in children born at term. The secondary aim was to ascertain if the potential for prevention of these risk factors has been adequately explored. Method A MEDLINE search up to 31 July 2011 was completed, following the Meta-Analysis of Observational Studies in Epidemiology guidelines. Publications were reviewed to identify those with both a primary aim of identifying risk factors for all children or term-born children with CP and a cohort or case-control study design. Studies were examined for potential chance or systematic bias. The range of point estimates of relative risk is reported. Results From 21 articles meeting inclusion/exclusion criteria and at low risk of bias, data from 6297 children with CP and 3 804 791 children without CP were extracted. Ten risk factors for term-born infants were statistically significant in each study: placental abnormalities, major and minor birth defects, low birthweight, meconium aspiration, instrumental/emergency Caesarean delivery, birth asphyxia, neonatal seizures, respiratory distress syndrome, hypoglycaemia, and neonatal infections. Strategies for possible prevention currently exist for three of these. Interpretation Ten consistent risk factors have been identified, some with potential for prevention. Efforts to prevent these risk factors to interrupt the pathway to CP should be extended.
Faculty of Health Sciences, The University of Sydney, Lidcombe, NSW 1825, Australia. email@example.com
Muscle vibration excites muscle spindles and creates illusory movement of a body part in a blindfolded individual. It is followed by an aftereffect, an illusion of return movement when vibration stops. The aftereffect reflects adaptation in the proprioceptive system. This adaptation is susceptible to attentional manipulations (Seizova-Cajic and Azzi in Exp Brain Res 203(1):213-219, 2010), but it is not known whether it is open to cross-modal influences unaided by those manipulations. We attempted to answer this question by allowing vision of the vibrated, stationary arm. We asked our participants (n = 20) to retain focus on the feeling of movement. They reported any illusory movement during 60-s biceps vibration (at 90 Hz), as well as following its offset, when vision of the arm was removed. During vibration, the proprioceptive movement illusion persisted, although the stationary arm was visible, but its duration and strength were much reduced in comparison with the no-vision condition. The movement aftereffect, experienced in total darkness following vibration offset, was also substantially weaker. The results show that proprioceptive adaptation is strongly modulated by vision. We propose that two processes contribute: perceptual (cross-modal binding with conflicting vision reduces the proprioceptive movement signal) and attentional (view of a stationary arm distracts from the proprioceptive movement signal). Our finding that during vibration, participants felt movement in the arm they could see, which was stationary, shows that cross-modal binding partially failed. This happened because the two percepts were too discrepant. However, only one-the visual-appeared real, and we argue that such an outcome is consistent with general principles of intersensory integration.
Cerebral Palsy Institute, PO Box 560, Darlinghurst, 1300 NSW, Australia. firstname.lastname@example.org
OBJECTIVES For singletons with cerebral palsy (CP) who were born at term, the goals were (1) to determine the proportion not admitted to a Special Care Unit/NICU (NICU),(2) to compare clinical descriptions of those admitted to NICUs and those not admitted, and (3) to identify neonatal predictors of CP among those not admitted to a NICU. METHODS A total-population case-(N = 442) control (N = 468) study of, singleton, term-born infants with CP, as ascertained from the Western Australian Cerebral Palsy Register, was performed. RESULTS All types of CP were represented among the 67% of term infants with CP (N = 295) who were not admitted to a NICU, which also included 54% of the subjects with the most severe impairments. Independent neonatal predictors were abnormalities of tone (odds ratio [OR]: 7.3 [95% confidence interval [CI]: 2-26.8]), temperature regulation (OR: 4.1 [95% CI: 1.2-14]), consciousness (OR: 3.7 [95% CI: 2-7]), and fontanelles (OR: 4.4 [95% CI: 0.8-23]), requirement for resuscitation (OR: 2.9 [95% CI: 2.2-12.9]), and birth defects (OR: 5.1 [95% CI: 2.4-10]). The risk of CP increased with the number of factors, but 58% of subjects who were not admitted to a NICU exhibited none of these factors. CONCLUSIONS Neonatal predictors of CP among term infants not admitted to a NICU were identified. However, 39% of all term singletons with CP were not admitted to a NICU and exhibited none of these predictors.
School of Medicine, Sydney, The University of Notre Dame Australia and Cerebral Palsy Institute, Darlinghurst, New South Wales, Australia.
Faculty of Health Sciences, University of Sydney, Lidcombe, NSW, 1825, Australia, email@example.com.
Visual processing of basic perceptual attributes depends on attention. This has been well documented since the surprising initial report on attentional modulation of the visual motion aftereffect (Chaudhuri 1990). Here, we investigate proprioception and show for the first time that attention modulates adaptation to perceived limb movement. We used biceps vibration to induce illusory forearm extension in 10 participants and measured the aftereffect-perceived movement in the opposite direction. The aftereffect was largest when participants focused on the illusory extension during the adaptation period. To divert attention away from the illusory extension, a rapid serial visual presentation task was performed during the adaptation. The aftereffect was much smaller in this condition, indicating interference between the visual task and proprioceptive adaptation. In tests of an analogous interaction between audition and vision, earlier research found no effect. We suggest that conscious proprioception requires more attention than conscious processing of visual or auditory input.
Consensus research priorities for cerebral palsy: a Delphi survey of consumers, researchers, and clinicians.
Cerebral Palsy Institute, Sydney, New South Wales, Australia. firstname.lastname@example.org
AIM Research funds for cerebral palsy are scarce and competition for them is strong. This study aimed to identify questions for future research that were agreed to be a high priority. METHOD An expert panel of consumers, researchers, and clinicians was assembled (n=127) and surveyed using a Delphi survey comprising three rounds. In round I, participants identified three important research topics. Three parallel surveys were constructed:(1) consumers;(2) intervention researchers and clinicians; and (3) aetiology and prevention researchers. In rounds II and III, participants rated priorities using a seven-point Likert scale. Questions reaching consensus were itemized and those not reaching consensus were discarded. RESULTS Consumers identified questions in the themes of prevention/cure, quality of life/community participation, and service provision/intervention. Intervention researchers/clinicians identified questions in the themes of effective outcomes and effective research/services. Aetiology and prevention researchers identified questions in the themes of infection/inflammation, focus on timing, haematology, research tools, neuroregeneration, and genetics. Fifty per cent of the consumers' priorities were also identified by professionals. INTERPRETATION Research priorities change as evidence is established. Phase II of this project is to develop a web portal with international collaboration. As evidence builds for one research question, it will be added to the web portal and unanswered questions will become the priority.
Faculty of Health Sciences, University of Sydney, Lidcombe, NSW 1825, Australia. email@example.com
We report an aftereffect in perception of the extent (or degree or range) of joint movement, showing for the first time that a prolonged exposure to a passive back-and-forth movement of a certain extent results in a change in judgment of the extent of a subsequently presented movement. The adapting stimulus, movement about the wrist, had an extent of either 30 degrees or 75 degrees , while the test stimulus was a 50 degrees movement. Following a 4-min adaptation period, the estimated magnitudes of the test stimuli were 61 degrees and 36 degrees in the 30 degrees and 75 degrees condition, respectively (t test(6)= 9.6; p < 0.001). The observed effect is an instance of repulsion or contrast commonly described in perception literature, with perceived value of the test stimulus pushed away from the adapting stimulus.
School of Psychology, Brennan MacCallum Building (A18), University of Sydney, Sydney, NSW 2006, Australia. firstname.lastname@example.org
While viewing an unambiguously rotating circular array of bars for an extended period, most perceive the array to occasionally move in the direction opposite to its true motion. We find that this alternation in perception has similar dynamics to rivalry, including little correlation among the durations of successive percepts. We also describe analogous reversals in touch and in proprioception. In the proprioceptive case, biceps vibration induces illusory forearm extension. Occasionally, although the same stimulation continues, reversals occur-flexion is perceived rather than extension. Temporal sampling is often invoked to explain the visual reversals but it cannot explain these proprioceptive reversals. Instead, after initial adaptation to the stimulus, rivalry between signals indicating the opposing directions could potentially explain reversals in all three modalities.
School of Psychology, University of Sydney, Sydney, New South Wales, Australia. email@example.com
BACKGROUND Adaptation to constant stimulation has often been used to investigate the mechanisms of perceptual coding, but the adaptive processes within the proprioceptive channels that encode body movement have not been well described. We investigated them using vibration as a stimulus because vibration of muscle tendons results in a powerful illusion of movement. METHODOLOGY/PRINCIPAL FINDINGS We applied sustained 90 Hz vibratory stimulation to biceps brachii, an elbow flexor and induced the expected illusion of elbow extension (in 12 participants). There was clear evidence of adaptation to the movement signal both during the 6-min long vibration and on its cessation. During vibration, the strong initial illusion of extension waxed and waned, with diminishing duration of periods of illusory movement and occasional reversals in the direction of the illusion. After vibration there was an aftereffect in which the stationary elbow seemed to move into flexion. Muscle activity shows no consistent relationship with the variations in perceived movement. CONCLUSION We interpret the observed effects as adaptive changes in the central mechanisms that code movement in direction-selective opponent channels.
Latest similar papers:
J Vis. 2012 ;12 (2): 22353778
Veterans Administration, Martinez, USA. firstname.lastname@example.org
Previous studies of localization of stationary targets in the peripheral visual field have found either underestimations (foveal biases) or overestimations (peripheral biases) of target eccentricity. In the present study, we help resolve this inconsistency by demonstrating the influence of visual boundaries on the type of localization bias. Using a Goldmann perimeter (an illuminated half-dome), we presented targets at different eccentricities across the visual field and asked participants to judge the target locations. In Experiments 1 and 2, participants reported target locations relative to their perceived visual field extent using either a manual or verbal response, with both response types producing a peripheral bias. This peripheral localization bias was a non-linear scaling of perceived location when the visual field was not bounded by external borders induced by facial features (i.e., the nose and brow), but location scaling was linear when visual boundaries were present. Experiment 3 added an external border (an aperture edge placed in the Goldmann perimeter) that resulted in a foveal bias and linear scaling. Our results show that boundaries that define a spatial region within the visual field determine both the direction of bias in localization errors for stationary objects and the scaling function of perceived location across visual space.
Aix-Marseille Univ, UMR 6233 Institute of Movement Sciences, 13288 Marseille, France.
In order to accurately localize an object, human observers must integrate multiple sensory cues related to the environment and/or to the body. Such multisensory integration must be repeated over time, so that spatial localization is constantly updated according to environmental changes. In the present experimental study, we examined the multisensory integration processes underlying spatial updating by investigating how gradual modifications of gravitoinertial cues (i.e., somatosensory and vestibular cues) and visual cues affect target localization skills. These were assessed by using a continuous pointing task toward a body-fixed visual target. The "single" rotation of the gravitoinertial vector (produced by off-axis centrifugation) resulted in downward pointing errors, which likely were related to a combination of oculogravic and somatogravic illusions. The "single" downward pitch rotation of the visual background produced an elevation of the arm relative to the visual target, suggesting that the rotation of the visual background caused an illusory target elevation (induced-motion phenomenon). Strikingly, the errors observed during the "combined" rotation of the visual background and of the gravitoinertial vector appeared as a linear combination of the errors independently observed during "single" rotations. In other words, the centrifugation effect on target localization was reduced by the visual background rotation. The observed linear combination indicates that the weights of visual and gravitoinertial cues were similar and remained constant throughout the stimulation.
Delayed pointing movements to masked Müller-Lyer figures are affected by target size but not the illusion.
Institute of Human Performance, University of Hong Kong, 111-113 Pokfulam Road, Hong Kong SAR, China. email@example.com
There is ongoing debate with respect to interpretation of the finding that, in contrast to perceptual size judgments, actions are relatively unaffected by the Müller-Lyer illusion. In normal unrestricted viewing situations observers cannot perform an action directed at an object without simultaneously perceiving the object - this makes it difficult to unequivocally establish whether observed effects are a function of vision for perception, vision for action, a combination of both, or of a single all-purpose visual system. However, there is evidence that observers are capable of performing actions towards objects of which they are not consciously aware, implying that two distinct visual thresholds may exist; one accompanying vision for action and one accompanying vision for perception. To investigate this possibility we created a situation in which visual information was presented below the perception threshold, but above the purported action threshold, allowing examination of action responses independent of contributions from vision for perception. Following a perceptual categorization task, participants performed delayed pointing movements towards briefly exposed masked Müller-Lyer targets of different sizes. When the targets were presented below the perception threshold, participants were unable to discriminate between them, yet their delayed pointing movements were affected by target size (but not the illusion). The results imply that vision for action is functional even after a delay and/or that the pickup of egocentric information is associated with a lower visual threshold than the pickup of allocentric information.
Leg muscle vibration modulates bodily self-consciousness: integration of proprioceptive, visual, and tactile signals.
Laboratory of Cognitive Neuroscience, Brain-Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 19, 1015 Lausanne, Switzerland. firstname.lastname@example.org
Behavioral studies have used visuo-tactile conflicts between a participant's body and a visually presented fake or virtual body to investigate the importance of bodily perception for self-consciousness (bodily self-consciousness). Illusory self-identification with a fake body and changes in tactile processing--modulation of visuo-tactile cross-modal congruency effects (CCEs)--were reported in previous findings. Although proprioceptive signals are deemed important for bodily self-consciousness, their contribution to the representation of the full body has not been studied. Here we investigated whether and how self-identification and tactile processing (CCE magnitude) could be modified by altering proprioceptive signals with 80-Hz vibrations at the legs. Participants made elevation judgments of tactile cues (while ignoring nearby lights) during synchronous and asynchronous stroking of a seen fake body. We found that proprioceptive signals during vibrations altered the magnitude of self-identification and mislocalization of touch (CCE) in a synchrony-dependent fashion: we observed an increase of self-identification and CCE magnitude during asynchronous stroking. In a second control experiment we studied whether proprioceptive signals per se, or those from the lower limbs in particular, were essential for these changes. We applied vibrations at the upper limbs (which provide no information about the position of the participant's body in space) and in this case observed no modulation of bodily self-consciousness or tactile perception. These data link proprioceptive signals from the legs that are conveyed through the dorsal column-medial lemniscal pathway to bodily self-consciousness. We discuss their integration with bodily signals from vision and touch for full-body representations.
Helmholtz Institute, Utrecht University, Heidelberglaan 2, 3584 Utrecht, The Netherlands. email@example.com
Bodily illusions differently affect body representations underlying perception and action. We investigated whether this task dependence reflects two distinct dimensions of embodiment: the sense of agency and the sense of the body as a coherent whole. In experiment 1 the sense of agency was manipulated by comparing active versus passive movements during the induction phase in a video rubber hand illusion (vRHI) setup. After induction, proprioceptive biases were measured both by perceptual judgments of hand position, as well as by measuring end-point accuracy of subjects' active pointing movements to an external object with the affected hand. The results showed, first, that the vRHI is largely perceptual: passive perceptual localisation judgments were altered, but end-point accuracy of active pointing responses with the affected hand to an external object was unaffected. Second, within the perceptual judgments, there was a novel congruence effect, such that perceptual biases were larger following passive induction of vRHI than following active induction. There was a trend for the converse effect for pointing responses, with larger pointing bias following active induction. In experiment 2, we used the traditional RHI to investigate the coherence of body representation by synchronous stimulation of either matching or mismatching fingers on the rubber hand and the participant's own hand. Stimulation of matching fingers induced a local proprioceptive bias for only the stimulated finger, but did not affect the perceived shape of the hand as a whole. In contrast, stimulation of spatially mismatching fingers eliminated the RHI entirely. The present results show that (i) the sense of agency during illusion induction has specific effects, depending on whether we represent our body for perception or to guide action, and (ii) representations of specific body parts can be altered without affecting perception of the spatial configuration of the body as a whole.
Faculty of Health and Behavioural Sciences, School of Psychology, University of Wollongong, Wollongong, NSW 2500, Australia. firstname.lastname@example.org
Eye movements help capture optic-flow information necessary to perceive visually our self motion. Visual and vestibular systems control compensatory eye movements that serve to stabilize the retinal images we capture. We examined the role that these eye movements may play in generating visual illusions of self motion (or vection). Observers viewed radially expanding optic-flow displays while performing lateral translational head oscillations at 1 Hz. Simulated viewpoint changes in these displays were synchronized with head movements, either in an ipsilateral (minimal sensory conflict) or a contralateral (high sensory conflict) direction. In control conditions, the observer viewed purely radial displays. Vection-onset latency and overall vection strength ratings were recorded, as well as horizontal eye movements. Vection onsets and strength ratings were significantly greater when the observer's head movements were incorporated into the visual displays. However, vection strength ratings were very similar for both ipsilateral and contralateral active display oscillation. Surprisingly, the non-ecological contralateral viewpoint oscillation actually induced vection earlier, despite the relatively small eye-in-head rotations coordinating gaze in these conditions. Our results support the view that compensatory eye movements are controlled through cooperative visual and vestibular interactions, and show that linear vection is highly robust against large sensory conflicts.
Department of Experimental Medicine, Section of Human Physiology and Istituto Nazionale di Neuroscienze, University of Genoa, Italy. email@example.com
Balance control depends on the interaction of multiple inputs originating from different sensory systems. Here, we investigated the effect on quiet human stance of changing the visual condition prior to a proprioceptive perturbation produced by vibration of dorsal neck muscles. In complete absence of visual references, the amplitude of the postural responses to neck vibration (forward shift of the centre of foot pressure) was the largest and became progressively larger as a function of the repetition of administered stimuli. The posture-destabilizing effect of vibration eyes-closed (EC) and the build-up effect were reduced if vibration was preceded by a period during which vision was allowed (EO). Similarly, the small destabilizing effect of vibration EO was increased if vibration was preceded by an EC period. The fore-period must last more than 3 s in order to affect the response to neck muscle vibration. The responsiveness to a proprioceptive disturbing input does not immediately change on adding or subtracting vision, but a finite time period must elapse before the postural "set" defined by vision is fully established. The findings underline the importance of time when vision is used in re-weighting the excitability of the postural control mechanisms.
Department of Neurophysiology, Tokyo Metropolitan Institute for Neurosciences, 2-6 Murashidai, Fuchu City, Tokyo, 183, Japan.
In the parietal association area of alert monkeys, a peculiar type of visual tracking neurons (VT neurons) were found in the posterior part of area 7. These cells were excited not only by the act of tracking but also by movement of a frame around the stationary target fixated by the monkey. The latter stimulation was the same as used to evoked visual illusion of "induced movement". This dual sensitivity of the VT neurons to real and induced movements of the target suggests that these neurons are closely related to motion perception of visual target.
The influence of retinal and extra-retinal motion cues on perceived object motion during self-motion.
Centre for Vision Research, York University, Toronto, Ontario, Canada. firstname.lastname@example.org
Eye, head, and body movement are intimately linked. During self-motion, the eyes track objects by a combination of vestibular reflexes and smooth pursuit eye movements but although the world appears stable during saccadic gaze changes, it does not appear stable during physical self-motion. We determined the amount by which a fixated object needed to be moved in space in order to appear earth stationary to a linearly moving observer. Observers were oscillated sinusoidally either passively or under their own control, under lit and fully darkened conditions. The visual targets always needed to move (in space) in the same direction as the observer to be judged as earth stationary. Targets needed to be moved more in order to be judged as earth stationary when movement was in the dark, rather than in the light, and also when movement was passive rather than when it was active. Efference copy motor signals, visual movement, and non-visual cues all contribute significantly and approximately additively to the estimate of self-motion. Errors in perceived self-motion can produce subsequent illusory visual motion.
Res. Inst. of Environ. Medicine, Nagoya Univ., Japan.
Gravity modifies us without our knowing it. Possible functional disabilities of eye, head and body movements were investigated under 1G and microgravity environments to evaluate the gravity cue for human behavior. The system for visual stability might be explained from the viewpoint of coordination between eye and head under microgravity. It is important to ascertain the significance of gravity in the maintenance of human visual stability. Coordination of eye position and head motion behavior by neck muscle discharge was examined in the mission SL-J, as well as a subjective evaluation of visual stability during spaceflight. There are a lot of discussion about human behavior contingent with gravity which has not been discussed ever.