Torsional eye movements in humans

If one has to give a description of eye movements, what first comes to mind is the possibility of the eyes to rotate in horizontal and vertical directions. It is generally less obvious that the eyes are capable of moving in a third. namely the torsional. direction. This capability is by no means hypothetical: humans, as well as other species, possess eye muscles that are pulling in torsional direction and orbital mechanics do allow for a certain amount of torsion. Definition of torsion Torsional eye movements can be defined in two different ways, namely as a rotation about the line of sight and as a rotation about an antero-posterior (forward-to-backward) axis that is fixed in the head

Eye mechanics and their implications for eye movement control

The topic of this thesis is the investigation of the mechanical properties of the oculomotor system and the implications of these properties for eye movement control. The investigation was conducted by means of computer models and simulations. This allowed us to combine data from anatomy, physiology and psychophysics with basic principles of physics (mechanics) and mathematics (geometry). In chapter 2 we investigate the degree to which mechanical and neural non-linearities contribute to the kinematic differences between centrifugal and centripetal saccades. On the basis of the velocity profiles of centrifugal and centripetal saccades we calculate the forces and muscle innervations during these eye movements. This was done using an inverted model of the eye plant. Our results indicate that the non-linear force-velocity relationship (i.e. muscle viscosity) of the muscles is probably the cause of the kinematic differences between centrifugal and centripetal saccades. In chapter 3 we calculate the adjustment of the saccadic command that is necessary to compensate for the eye plant non-linearities. These calculations show that the agonist and antagonist muscles require different net saccade signal gain changes. In order to better understand how this gain change is accomplished we use the inverted model of the eye plant (chapter 2) to calculate the muscle innervation profiles of saccades with different starting orientations. Based on these calculations we conclude that the saccade signal gain changes are accomplished primarily by changes in the magnitude of the saccade signal. In chapter 4 we examine the requirements that the oculomotor system must meet for the eye to be able to make desired gaze changes and fixate at various eye orientations. We first determine how the axes of action (i.e. unit moment vectors) of the muscles are related to eye orientation and the location of the effective muscle origin (i.e. the muscle pulleys). Next we show how this relation constrains muscle pulley locations if the eye movements are controlled by specific rules. The two control theories we investigate are: 1. Eye movements that obey Listing's law, and the binocular extension of Listing's law, actively use only the horizontal and vertical muscle pairs. 2. Oculomotor control involves perfect agonist-antagonist muscle alignment. In chapter 5 we test two assumptions that are commonly made in models of the oculomotor plant. The first is the assumption that the antagonistic muscles can be viewed as a single bi-directional muscle. The second is the assumption that the three muscle pairs act in orthogonal directions. On the basis of the geometrical properties governing the muscle paths we show how these assumptions give rise to incorrect predictions for the oculomotor control signals. Using the same muscle activation patterns for eye plant models with and without these assumptions we calculate the eye orientations that are reached. Finally in chapter 6 we discuss some general conclusions concerning the consequences of the mechanics of the eye for oculomotor control

Humanoid Robots

For many years, the human being has been trying, in all ways, to recreate the complex mechanisms that form the human body. Such task is extremely complicated and the results are not totally satisfactory. However, with increasing technological advances based on theoretical and experimental researches, man gets, in a way, to copy or to imitate some systems of the human body. These researches not only intended to create humanoid robots, great part of them constituting autonomous systems, but also, in some way, to offer a higher knowledge of the systems that form the human body, objectifying possible applications in the technology of rehabilitation of human beings, gathering in a whole studies related not only to Robotics, but also to Biomechanics, Biomimmetics, Cybernetics, among other areas. This book presents a series of researches inspired by this ideal, carried through by various researchers worldwide, looking for to analyze and to discuss diverse subjects related to humanoid robots. The presented contributions explore aspects about robotic hands, learning, language, vision and locomotion

自然視条件下脳波計測の精度向上を可能にする眼球運動情報を用いた解析方法に関する研究

As the technique of electroencephalogram (EEG) developed for such many years, its application spreads and permeates into different areas, such like, clinical diagnosis, brain-computer interface, mental state estimation, and so on. Recently, using EEG as a tool for estimate people’s mental state and its extensional applications have jump into the limelight. These practical applications are urgently needed because the lack of subjectively estimating methods for the so called metal states, such as the concentration during study, the cognitive workload in driving, the calmness under mental training and so on. On the other hand, the application of EEG signals under daily life conditions especially when eye movements are totally without any constrains under a ‘fully free-view’ condition are obedient to the traditional ocular artifact suppression methods and how it meets the neuroscience standard has not been clearly expounded. This cause the ambiguities of explaining the obtain data and lead to susceptive results from data analysis. In our research, based on the basic idea of employing and extending EEG as the main tool for the estimation to mental state for daily life use, we confirmed the direction sensitivity of ocular artifacts induced by various types of eye movements and showed the most sensitive areas to the influence from it by multi zone-of-view experiment with standard neuroscience-targeted EEG devices. Enlightened from the results, we extended heuristic result on the use of more practical portable EEG devices. Besides, for a more realistic solution of the EEG based mental state estimation which is supposed to be applied for daily life environment, we studied the signal processing techniques of artifact suppression on low density electrode EEG and showed the importance of taking direction/eye position information into account when ocular artifact removal/suppression. In summary, this thesis has helped pave the practical way of using EEG signals toward the general use in daily life which has irregular eye movement patterns. We also pointed out the view-direction sensitivity of ocular artifact which helps the future studies to overcome the difficulties imposed on EEG applications by the free-view EEG tasks.九州工業大学博士学位論文 学位記番号:生工博甲第262号 学位授与年月日:平成28年3月26日1 Introduction|2 EEG measurements and ocular artifacts|3 Regression based solutions to ocular artifact suppression or removal in EEG|4 Measuring EEG with eye-tracking system|5 Direction and viewing area-sensitive influence of EOG artifacts revealed in the EEG topographic pattern analysis|6 Performance improvement of artifact removal with ocular information|7 Summary九州工業大学平成27年

The Fourier analysis of saccadic eye movements

This thesis examines saccadic eye movements in the frequency domain and develops sensitive tools for characterising their dynamics. It tests a variety of saccade models and provides the first strong empirical evidence that saccades are time-optimal. By enabling inferences on the neural command, it also allows for better clinical differentiation of abnormalities and the evaluation of putative mechanisms for the development of congenital nystagmus. Chapters 3 and 4 show how Fourier transforms reveal sharp minima in saccade frequency spectra, which are robust to instrument noise. The minima allow models based purely on the output trajectory, purely on the neural input, or both, to be directly compared and distinguished. The standard, most commonly accepted model based on bang-bang control theory is discounted. Chapter 5 provides the first empirical evidence that saccades are time-optimal by demonstrating that saccade bandwidths overlap across amplitude onto a single slope at high frequencies. In Chapter 6, the overlap also allows optimal (Wiener) filtering in the frequency domain without a priori assumptions. Deconvolution of the aggregate neural driving signal is then possible for current models of the oculomotor plant. The final two chapters apply these Fourier techniques to the quick phases of physiological (optokinetic) nystagmus and of pathological (congenital) nystagmus. These quick phases are commonly assumed to be saccadic in origin. This assumption is thoroughly tested and found to hold, but with subtle differences implying that the smooth pursuit system interacts with the saccade system during the movement. This interaction is taken into account in Chapter 8 in the assessment of congenital nystagmus quick phases, which are found to be essentially normal. Congenital nystagmus models based on saccadic abnormalities are appraised

Characterization of the torsional optokinetic response to rolling visual fields in humans

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992.Includes bibliographical references (leaves 324-330).by Dana Keoki Jackson.M.S

Visuomotor Coordination in Reach-To-Grasp Tasks: From Humans to Humanoids and Vice Versa

Understanding the principles involved in visually-based coordinated motor control is one of the most fundamental and most intriguing research problems across a number of areas, including psychology, neuroscience, computer vision and robotics. Not very much is known regarding computational functions that the central nervous system performs in order to provide a set of requirements for visually-driven reaching and grasping. Additionally, in spite of several decades of advances in the field, the abilities of humanoids to perform similar tasks are by far modest when needed to operate in unstructured and dynamically changing environments. More specifically, our first focus is understanding the principles involved in human visuomotor coordination. Not many behavioral studies considered visuomotor coordination in natural, unrestricted, head-free movements in complex scenarios such as obstacle avoidance. To fill this gap, we provide an assessment of visuomotor coordination when humans perform prehensile tasks with obstacle avoidance, an issue that has received far less attention. Namely, we quantify the relationships between the gaze and arm-hand systems, so as to inform robotic models, and we investigate how the presence of an obstacle modulates this pattern of correlations. Second, to complement these observations, we provide a robotic model of visuomotor coordination, with and without the presence of obstacles in the workspace. The parameters of the controller are solely estimated by using the human motion capture data from our human study. This controller has a number of interesting properties. It provides an efficient way to control the gaze, arm and hand movements in a stable and coordinated manner. When facing perturbations while reaching and grasping, our controller adapts its behavior almost instantly, while preserving coordination between the gaze, arm, and hand. In the third part of the thesis, we study the neuroscientific literature of the primates. We here stress the view that the cerebellum uses the cortical reference frame representation. The cerebellum by taking into account this representation performs closed-loop programming of multi-joint movements and movement synchronization between the eye-head system, arm and hand. Based on this investigation, we propose a functional architecture of the cerebellar-cortical involvement. We derive a number of improvements of our visuomotor controller for obstacle-free reaching and grasping. Because this model is devised by carefully taking into account the neuroscientific evidence, we are able to provide a number of testable predictions about the functions of the central nervous system in visuomotor coordination. Finally, we tackle the flow of the visuomotor coordination in the direction from the arm-hand system to the visual system. We develop two models of motor-primed attention for humanoid robots. Motor-priming of attention is a mechanism that implements prioritizing of visual processing with respect to motor-relevant parts of the visual field. Recent studies in humans and monkeys have shown that visual attention supporting natural behavior is not exclusively defined in terms of visual saliency in color or texture cues, rather the reachable space and motor plans present the predominant source of this attentional modulation. Here, we show that motor-priming of visual attention can be used to efficiently distribute robot's computational resources devoted to visual processing

The human eye-movement response to maintained surface galvanic vestibular stimulation

Contains fulltext : 141356.pdf (publisher's version ) (Closed access