Postural control in quiet standing is often explained by a reflexive response to optical flow, the apparent motion of environmental objects in a visual scene. However, moving room experiments show ...that even small-amplitude body sway can evoke odd sensations or motion sickness, indicating that a consciousness factor may also be involved. Studies targeting perception of self-motion, vection, typically use rapid visual stimuli moving in a single direction to maintain a constant feeling of vection, and there are few studies of vection using low-speed sinusoidal visual stimuli similar to human pendular movement. In the present study we searched for changes in postural control during periods of vection during quiet standing. Participants (N = 19, age = 20.4 ±1.1 years) were shown dynamic visual stimuli in the form of sinusoidally expanding and contracting random dots, and the stimuli speed and visual field were manipulated. Posture was continually evaluated using Center of Pressure (CoP) measurements. Participants were also asked to report feelings of vection, both by pressing a button during the trial and through an overall rating at the end of each trial. Using repeated-measures ANOVA, we assessed changes in the CoP and vection variables between experimental conditions, as well as possible interactions between the variables. The results show that postural reaction and vection were both affected by the visual stimuli and varied with speed. The peripheral visual field was found to couple to stronger feeling of vection and better quality of postural control. However, no significant relationship between postural control and vection, nor evidence of vection interaction to the relationship between optical flow and postural control, was found. Based on our results we conclude that for postural stability during quiet standing, visual cues dominate over any potential consciousness factor arising due to vection.
The perception of moving objects (real motion) is a critical function for interacting with a dynamic environment. Motion perception can be also induced by particular structural features of static ...images (illusory motion) or by photographic images of subjects in motion (implied motion, IM). Many cortical areas are involved in motion processing, particularly the medial temporal cortical area (MT), dedicated to the processing of real, illusory, and implied motion. Recently, there has been a growing interest in the influence of high-level visual processes on pupillary responses. However, just a few studies have measured the effect of motion processing on the pupil, and not always with consistent results. Here we systematically investigate the effects of real, illusory, and implied motion on the pupil diameter for the first time, by showing different types of stimuli (movies, illusions, and photos) with the same average luminance to the same observers. We find different pupillary responses depending on the nature of motion. Real motion elicits a larger pupillary dilation than IM, which in turn induces more dilation than control photos representing static subjects (No-IM). The pupil response is sensitive even to the strength of IM, as photos with enhanced IM (blur, motion streaks, speed lines) induce larger dilation than simple freezed IM (subjects captured in the instant they are moving). Also, the subject represented in the stimulus matters: human figures are interpreted as more dynamic and induce larger dilation than objects/animals. Interestingly, illusory motion induces much less dilation than all the other motion categories, despite being seen as moving. Overall, pupil responses depend on the individual perception of dynamicity, confirming that the pupil is modulated by the subjective interpretation of complex stimuli. We argue that the different pupillary responses to real, illusory, and implied motion reflect the top-down modulations of different cortical areas involved in their processing.
Hollywood's Indies offers an in depth examination of the phenomenon of the classics divisions by tracing its history since the establishment of the first specialty label in 1980.
What do Chinese literature and film inspired by the Cultural Revolution (1966-1976) have in common with media of the May Fourth movement (1918-1930)? This book demonstrates several shared aims: to ...liberate narrative arts from aesthetic orthodoxies, to draw on foreign sources for inspiration, and to free individuals from social conformity.
Active Brownian motion tunable by light Buttinoni, Ivo; Volpe, Giovanni; Kümmel, Felix ...
Journal of physics. Condensed matter,
07/2012, Letnik:
24, Številka:
28
Journal Article
Recenzirano
Odprti dostop
Active Brownian particles are capable of taking up energy from their environment and converting it into directed motion; examples range from chemotactic cells and bacteria to artificial ...micro-swimmers. We have recently demonstrated that Janus particles, i.e. gold-capped colloidal spheres, suspended in a critical binary liquid mixture perform active Brownian motion when illuminated by light. In this paper, we investigate in more detail their swimming mechanism, leading to active Brownian motion. We show that the illumination-borne heating induces a local asymmetric demixing of the binary mixture, generating a spatial chemical concentration gradient which is responsible for the particle's self-diffusiophoretic motion. We study this effect as a function of the functionalization of the gold cap, the particle size and the illumination intensity: the functionalization determines what component of the binary mixture is preferentially adsorbed at the cap and the swimming direction (towards or away from the cap); the particle size determines the rotational diffusion and, therefore, the random reorientation of the particle; and the intensity tunes the strength of the heating and, therefore, of the motion. Finally, we harness this dependence of the swimming strength on the illumination intensity to investigate the behavior of a micro-swimmer in a spatial light gradient, where its swimming properties are space-dependent.
We study four-derivative corrections to four-dimensional N = 2 minimal gauged supergravity controlled by two real constants. The solutions of the equations of motion in the two-derivative theory are ...not modified by the higher-derivative corrections. We use this to derive a general formula for the regularized on-shell action for any asymptotically locally AdS4 solution of the theory and show how the higher-derivative corrections affect black hole thermodynamic quantities in a universal way. We employ our results in the context of holography to derive explicit expressions for the subleading corrections in the large N expansion of supersymmetric partition functions on various compact manifolds for a large class of three-dimensional SCFTs.
Cartoons in Hard Times provides a comprehensive analysis of the short subject animation released by the Walt Disney and Warner Brothers from 1932 and 1945, one of the most turbulent periods in Unites ...States history. Through a combination of content analysis, historical understanding and archival research, this book sheds new light on a hitherto unexplored area of animation, suggesting the ways in which Disney and Warner Brothers animation engaged with historical, social, economic and political changes in this era. The book also traces the development of animation into a medium fit for propaganda in 1941 and the changes in characters, tone, music and narrative that took place to facilitate this transition. Animation transformed in this era from a medium of entertainment, to a socio-political commentator before finally undertaking government sponsored propaganda during the Second World War. N.B. Please ensure that any images originally supplied in colour are supplied in greyscale for print deliverables (print and POD PDFs) and colour for all others (including eBook and XML).
Anecdotal reports suggest that motion sickness may occur among users of contemporary, consumer-oriented head-mounted display systems and that women may be at greater risk. We evaluated the ...nauseogenic properties of one such system, the
Oculus Rift
. The head-mounted unit included motion sensors that were sensitive to users’ head movements, such that head movements could be used as control inputs to the device. In two experiments, seated participants played one of two virtual reality games for up to 15 min. In Experiment 1, 22% of participants reported motion sickness, and the difference in incidence between men and women was not significant. In Experiment 2, motion sickness was reported by 56% of participants, and incidence among women (77.78%) was significantly greater than among men (33.33%). Before participants were exposed to the head-mounted display system, we recorded their standing body sway during the performance of simple visual tasks. In both experiments, patterns of pre-exposure body sway differed between participants who (later) reported motion sickness and those who did not. In Experiment 2, sex differences in susceptibility to motion sickness were preceded by sex differences in body sway. These postural effects confirm a prediction of the postural instability theory of motion sickness. The results indicate that users of contemporary head-mounted display systems are at significant risk of motion sickness and that in relation to motion sickness these systems may be sexist in their effects.
Background
In magnetic resonance (MR)‐guided thermal therapy, respiratory motion can cause a significant temperature error in MR thermometry and reduce the efficiency of the treatment. A respiratory ...motion simulator is necessary for the development of new MR imaging (MRI) and motion compensation techniques.
Purpose
The purpose of this study is to develop a low‐cost and simple MR‐compatible respiratory motion simulator to support proof‐of‐concept studies of MR monitoring approaches with respiratory‐induced abdominal organ motion.
Methods
The phantom motion system integrates pneumatic control via an actuator subsystem located outside the MRI and coupled via plastic tubing to a compressible bag for distention and retraction within the MRI safe motion subsystem and phantom positioned within the MRI scanner. Performance of the respiratory motion simulator was evaluated with a real‐time gradient echo MRI pulse sequence.
Results
The motion simulator can produce respiratory rates in the range of 8–16 breaths/min. Our experiments showed the consistent periodic motion of the phantom during MRI acquisition in the range of 3.7–9 mm with 16 breaths/min. The operation of the simulator did not cause interference with MRI acquisition.
Conclusions
In this study, we have demonstrated the ability of the motion simulator to generate controlled respiratory motion of a phantom. The low‐cost MR‐compatible respiratory motion simulator can be easily constructed from off‐the‐shelf and 3D‐printed parts based on open‐source 3D models and instructions. This could lower the barriers to the development of new MRI techniques with motion compensation.
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