Do Balance Demands Induce Shifts in Visual Proprioception in Crawling Infants?

The onset of hands-and-knees crawling during the latter half of the first year of life heralds pervasive changes in a range of psychological functions. Chief among these changes is a clear shift in visual proprioception, evident in the way infants use patterns of optic flow in the peripheral field of view to regulate their postural sway. This shift is thought to result from consistent exposure in the newly crawling infant to different patterns of optic flow in the central field of view and the periphery and the need to concurrently process information about self-movement, particularly postural sway, and the environmental layout during crawling. Researchers have hypothesized that the demands on the infant's visual system to concurrently process information about self-movement and the environment press the infant to differentiate and functionalize peripheral optic flow for the control of balance during locomotion so that the central field of view is freed to engage in steering and monitoring the surface and potentially other tasks. In the current experiment, we tested whether belly crawling, a mode of locomotion that places negligible demands on the control of balance, leads to the same changes in the functional utilization of peripheral optic flow for the control of postural sway as hands-and-knees crawling. We hypothesized that hands-and-knees crawlers (n = 15) would show significantly higher postural responsiveness to movements of the side walls and ceiling of a moving room than same-aged pre-crawlers (n = 19) and belly crawlers (n = 15) with an equivalent amount of crawling experience. Planned comparisons confirmed the hypothesis. Visual-postural coupling in the hands-and-knees crawlers was significantly higher than in the belly crawlers and pre-crawlers. These findings suggest that the balance demands associated with hands-and-knees crawling may be an important contributor to the changes in visual proprioception that have been demonstrated in several experiments to follow hands-and-knees crawling experience. However, we also consider that belly crawling may have less potent effects on visual proprioception because it is an effortful and attention-demanding mode of locomotion, thus leaving less attentional capacity available to notice changing relations between the self and the environment

A Neural Model of Visually Guided Steering, Obstacle Avoidance, and Route Selection

A neural model is developed to explain how humans can approach a goal object on foot while steering around obstacles to avoid collisions in a cluttered environment. The model uses optic flow from a 3D virtual reality environment to determine the position of objects based on motion discontinuities, and computes heading direction, or the direction of self-motion, from global optic flow. The cortical representation of heading interacts with the representations of a goal and obstacles such that the goal acts as an attractor of heading, while obstacles act as repellers. In addition the model maintains fixation on the goal object by generating smooth pursuit eye movements. Eye rotations can distort the optic flow field, complicating heading perception, and the model uses extraretinal signals to correct for this distortion and accurately represent heading. The model explains how motion processing mechanisms in cortical areas MT, MST, and posterior parietal cortex can be used to guide steering. The model quantitatively simulates human psychophysical data about visually-guided steering, obstacle avoidance, and route selection.Air Force Office of Scientific Research (F4960-01-1-0397); National Geospatial-Intelligence Agency (NMA201-01-1-2016); National Science Foundation (SBE-0354378); Office of Naval Research (N00014-01-1-0624

A Neural Model of Visually Guided Steering, Obstacle Avoidance, and Route Selection

A neural model is developed to explain how humans can approach a goal object on foot while steering around obstacles to avoid collisions in a cluttered environment. The model uses optic flow from a 3D virtual reality environment to determine the position of objects based on motion discotinuities, and computes heading direction, or the direction of self-motion, from global optic flow. The cortical representation of heading interacts with the representations of a goal and obstacles such that the goal acts as an attractor of heading, while obstacles act as repellers. In addition the model maintains fixation on the goal object by generating smooth pursuit eye movements. Eye rotations can distort the optic flow field, complicating heading perception, and the model uses extraretinal signals to correct for this distortion and accurately represent heading. The model explains how motion processing mechanisms in cortical areas MT, MST, and VIP can be used to guide steering. The model quantitatively simulates human psychophysical data about visually-guided steering, obstacle avoidance, and route selection.Air Force Office of Scientific Research (F4960-01-1-0397); National Geospatial-Intelligence Agency (NMA201-01-1-2016); National Science Foundation (NSF SBE-0354378); Office of Naval Research (N00014-01-1-0624

The Role of Stereopsis in the Control of Grasp Forces during Prehension

Background: Binocular viewing is associated with a superior prehensile performance, which is particularly evident in the latter part of the reach as the hand approaches and makes contact with the target object. However, the visuomotor mechanisms through which binocular vision serves prehensile performance remains unclear. The present study was designed to investigate the role of stereopsis in the planning and control of grasping using outcome measures which reflect predictive control. It was hypothesized that binocular viewing will be associated with more efficient grasp execution because stereoacuity provides more accurate sensory input about the object’s material properties to plan appropriate grip forces to successfully lift the target object. In the case when binocular vision is reduced or unavailable, predictive control of grasping will be reduced, and subjects will have to rely on somatosensory feedback to successfully execute the grasp. Methods: 20 healthy participants (17-35 years, 11 male) with normal vision were recruited. Subjects performed a precision reach-to-grasp task which required them to reach, grasp, and transport a bead (~2 cm in diameter) to a specified location. Subjects were instructed to perform the task as fast as possible in the following viewing conditions: binocular, monocular, and two conditions with reduced stereoacuity: 200 arcsec stereo, 800 arcsec stereo, which were randomized in blocks. Results: Binocular, compared to monocular viewing had a greater influence on the grasp phase compared to the reach and transport phase. Specifically, there was a 36% increase in post-contact time, 29% decrease in grip force 50ms following object grasp, and 30% increase in grasp errors. In contrast, parameters of the reach and transport phase only demonstrated a 3-8% reduction in performance. Grasp performance was similarly disrupted during binocular viewing with reduced stereoacuity whereby a reduction in stereoacuity was associated with a proportional reduction in grasp performance. Notably, grip force at the time of object lift-off was comparable between all viewing conditions. Conclusion: The results demonstrate that binocular viewing contributes significantly more to the performance of grasping relative to the reach and transport phase. In addition, the results suggest that stereopsis provides important sensory information which enables the central nervous system to engage in predictive control of grasp forces. When binocular disparity information is reduced or absent, subjects take on a more cautious approach to the grasp and make more errors (i.e., collisions followed by readjustments). Overall, findings from the current study indicate that stereopsis provides important sensory input for the predictive control of grasping, and a progressive reduction in stereopsis is associated with increased uncertainty which results in a greater reliance on somatosensory feedback control

A Sparse Intraoperative Data-Driven Biomechanical Model to Compensate for Brain Shift during Neuronavigation

BACKGROUND AND PURPOSE: Intraoperative brain deformation is an important factor compromising the accuracy of image-guided neurosurgery. The purpose of this study was to elucidate the role of a model-updated image in the compensation of intraoperative brain shift. MATERIALS AND METHODS: An FE linear elastic model was built and evaluated in 11 patients with craniotomies. To build this model, we provided a novel model-guided segmentation algorithm. After craniotomy, the sparse intraoperative data (the deformed cortical surface) were tracked by a 3D LRS. The surface deformation, calculated by an extended RPM algorithm, was applied on the FE model as a boundary condition to estimate the entire brain shift. The compensation accuracy of this model was validated by the real-time image data of brain deformation acquired by intraoperative MR imaging. RESULTS: The prediction error of this model ranged from 1.29 to 1.91 mm (mean, 1.62 +/- 0.22 mm), and the compensation accuracy ranged from 62.8% to 81.4% (mean, 69.2 +/- 5.3%). The compensation accuracy on the displacement of subcortical structures was higher than that of deep structures (71.3 +/- 6.1%; 66.8 +/- 5.0%, P \u3c .01). In addition, the compensation accuracy in the group with a horizontal bone window was higher than that in the group with a nonhorizontal bone window (72.0 +/- 5.3%; 65.7 +/- 2.9%, P \u3c .05). CONCLUSIONS: Combined with our novel model-guided segmentation and extended RPM algorithms, this sparse data-driven biomechanical model is expected to be a reliable, efficient, and convenient approach for compensation of intraoperative brain shift in image-guided surgery

A method for the assessment of time-varying brain shift during navigated epilepsy surgery

Image guidance is widely used in neurosurgery. Tracking systems (neuronavigators) allow registering the preoperative image space to the surgical space. The localization accuracy is influenced by technical and clinical factors, such as brain shift. This paper aims at providing quantitative measure of the time-varying brain shift during open epilepsy surgery, and at measuring the pattern of brain deformation with respect to three potentially meaningful parameters: craniotomy area, craniotomy orientation and gravity vector direction in the images reference frame

Time for revision of seafarers vision testing?

No evidence-based vision test for selecting bridge crew considers the realistic, demanding vision requirements at sea. This may be the cause of serious accidents. A proposal is outlined for development of a test that recreate the visually demanding conditions at sea with video that provides 3D images of objects to be observed

Oštećenja vida uslijed diskinetskih poremećaja pokreta očiju u djece s diskinetskom cerebralnom paralizom

Despite the fact that ocular and cerebral visual abnormalities are shown to be very frequent in cerebral palsy (CP), children with CP are underreferred to rehabilitation services for visual impairments. Visual component is, together with the motor disorder, an integral part of the clinical picture of CP and not an associated symptom. Therefore, an accurate detection of visual disorders and visual function not only lead to a complete clinical diagnosis but also to an appropriate intervention plan. Hence, the need for a study aiming specifically to describe all the aspects of visual involvement in the dyskinetic CP. Research goals were aimed at gaining insights into the nature of visual impairments and functional vision of children with dyskinetic CP, determining the nature of connection between visual functions and functional vision, with an emphasis on searching for dyskinetic eye movement disorder for understanding the difficulties in performing visual activities of two children with dyskinetic CP from the Zagreb’s county register of CP, which is part of national C28 RCP-HR-Register of cerebral palsy of Croatia included in Surveillance Cerebral Palsy Europe (SCPE). The data were collected using standardized and non-standardized tests for visual function assessment. Dyskinetic eye movement disorder was tested comparing the tested results of visual functions. Functional vision was tested through the observation of the children’s behavior and through open structured questions addressed to parents. Cerebral visual impairment was examined by a questionnaire for cerebral visual impairment screening. Qualitative research analysis shows which ocular and cerebral visual impairments are present as well as their relation to visual functioning. Moreover, it shows clinical features of dyskinetic eye movement disorder that haven’t been shown present among tested children. Since this is the second research up to this date, testing an eye movement disorder that specifically occurs in dyskinetic CP, its characteristics are further discussed and defined. In contrary to previous study, in a child where highly inefficient visual functioning was shown, the cause goes wider from the abnormal eye motility. It consists of combination of several motor and sensory problems (lacking binocular visual acuity, contrast sensitivity, fixation, voluntary eye movements and oculomotricity). Due to the small sample and findings that are, on account of heterogeneity of dyskinetic CP hard to compare, future research is needed to expand overall knowledge of functional vision and visual functions needed for planning rehabilitation and education management for children with dyskinetic CP.Unatoč činjenici da su okularne i cerebralne vizualne abnormalnosti česte u cerebralnoj paralizi (CP), djeca s CP nedostatno podliježu uslugama rehabilitacije oštećenja vida. Vizualna komponenta je, zajedno s motoričkim poremećajem, sastavni dio kliničke slike CP, a ne samo pridruženi simptom. Točno otkrivanje vizualnog profila djece s CP dovodi do sveobuhvatne kliničke dijagnoze i do odgovarajućeg plana intervencije. Stoga je potrebna studija čiji je cilj opisati sve aspekte vizualne uključenosti u diskinetskom tipu CP. Ciljevi istraživanja bili su usmjereni na stjecanje uvida u prirodu vidnih funkcjia i funkcionalnog vida djece s diskinetskom CP, utvrđivanje prirode povezanosti vizualnih funkcija i funkcionalnog vida, s naglaskom na otkrivanje diskinetskog poremećaja pokreta očiju, kako bi se poboljšalo razumijevanje poteškoća u izvođenju vizualnih aktivnosti dvoje djece s diskinetskom CP iz zagrebačkog županijskog registra CP-a, koji je dio nacionalnog registra C28 RCP-HR cerebralne paralize Hrvatske uključen u Surveillance Cerebral Palsy Europe (SCPE). Podaci su prikupljeni korištenjem standardiziranih i nestandardiziranih testova za procjenu vidnih funkcija. Diskinetski poremećaj pokreta očiju testiran je uspoređujući testirane rezultate vidnih funkcija. Funkcionalni vid testiran je promatranjem dječjeg ponašanja u vizualnim zadacima i kroz otvorena strukturirana pitanja upućena roditeljima. Cerebralno oštećenje vida ispitano je upitnikom za screening na cerebralno oštećenje vida. Kvalitativna analiza podataka pokazuje koja su okularna i cerebralna oštećenja vida prisutna kao i njihov odnos prema funkcionalnom vidu. Budući da je ovo drugo do sada istraživanje ispitivanja diskinetskog poremećaja pokreta očiju koji je karakterističan za diskinetsku CP, opisana su njegova klinička obilježja. Suprotno već objavljenoj studiji, kod djeteta kod kojeg je prikazano vrlo neučinkovito vizualno funkcioniranje, uzrok je širi od abnormalne pokretljivosti oka. Sastoji se od kombinacije nekoliko motoričkih i senzoričkih problema (nedostatna binokularna oštrina vida, kontrastna osjetljivost, fiksacija, voljni pokreti očiju i okulomotorika). Zbog malog uzorka i nalaza koji su zbog heterogenosti diskinetičke CP teško usporedivi, potrebna su buduća istraživanja kako bi se proširilo sveukupno znanje o diskinetskom poremećaju pokreta očiju, funkcionalnom vidu i vizualnim funkcijama potrebnim za planiranje edukacije i rehabilitacije djece s diskinetskom CP

The assessment of visual behaviour and depth perception in surgery

Imperial Users onl