Dynamic Characteristics of a New Three-Dimensional Linear Homeomorphic Saccade Model.

A linear homeomorphic eye movement model that produces 3D saccadic eye movements consistent with anatomical and physiological evidence is introduced in this second part of a two-paper sequence. Central to the model is the implementation of a time-optimal neural control strategy involving six linear muscle models that faithfully represent the dynamic characteristics of 3D saccades. The muscle is modeled as a parallel combination of viscosity [Formula: see text] and series elasticity [Formula: see text], connected to the parallel combination of active-state tension generator [Formula: see text], viscosity element [Formula: see text], and length tension elastic element [Formula: see text]. The neural input for each muscle is separately maintained while the effective pulling direction is modulated by its respective pulley. The results demonstrate that a time-optimal, 2D commutative neural controller, together with the pulley system, actively functions to implement Listing's law during both static and dynamic simulations and provide an excellent match with the experimental data. The parameters and neural input to the muscles are estimated using a time domain system identification technique from saccade data, with an excellent match between the model estimates and the data. A total of 20 horizontal, 5 vertical and 62 oblique saccades are analyzed.

Static Characteristics of a New Three-Dimensional Linear Homeomorphic Saccade Model.

A linear homeomorphic saccade model that produces 3D saccadic eye movements consistent with physiological and anatomical evidence is introduced. Central to the model is the implementation of a time-optimal controller with six linear muscles and pulleys that represent the saccade oculomotor plant. Each muscle is modeled as a parallel combination of viscosity [Formula: see text] and series elasticity [Formula: see text] connected to the parallel combination of active-state tension generator [Formula: see text], viscosity element [Formula: see text], and length tension elastic element [Formula: see text]. Additionally, passive tissues involving the eyeball include a viscosity element [Formula: see text], elastic element [Formula: see text], and moment of inertia [Formula: see text]. The neural input for each muscle is separately maintained, whereas the effective pulling direction is modulated by its respective mid-orbital constraint from the pulleys. Initial parameter values for the oculomotor plant are based on anatomical and physiological evidence. The oculomotor plant uses a time-optimal, 2D commutative neural controller, together with the pulley system that actively functions to implement Listing's law during both static and dynamic conditions. In a companion paper, the dynamic characteristics of the saccade model is analyzed using a time domain system identification technique to estimate the final parameter values and neural inputs from saccade data. An excellent match between the model estimates and the data is observed, whereby a total of 20 horizontal, 5 vertical, and 64 oblique saccades are analyzed.

A neuron-based time-optimal controller of horizontal saccadic eye movements.

A neural network model of biophysical neurons in the midbrain for controlling oculomotor muscles during horizontal human saccades is presented. Neural circuitry that includes omnipause neuron, premotor excitatory and inhibitory burst neurons, long lead burst neuron, tonic neuron, interneuron, abducens nucleus and oculomotor nucleus is developed to investigate saccade dynamics. The final motoneuronal signals drive a time-optimal controller that stimulates a linear homeomorphic model of the oculomotor plant. To our knowledge, this is the first report on modeling the neural circuits at both premotor and motor stages of neural activity in saccadic systems.

A physiological neural controller of a muscle fiber oculomotor plant in horizontal monkey saccades.

A neural network model of biophysical neurons in the midbrain is presented to drive a muscle fiber oculomotor plant during horizontal monkey saccades. Neural circuitry, including omnipause neuron, premotor excitatory and inhibitory burst neurons, long lead burst neuron, tonic neuron, interneuron, abducens nucleus, and oculomotor nucleus, is developed to examine saccade dynamics. The time-optimal control strategy by realization of agonist and antagonist controller models is investigated. In consequence, each agonist muscle fiber is stimulated by an agonist neuron, while an antagonist muscle fiber is unstimulated by a pause and step from the antagonist neuron. It is concluded that the neural network is constrained by a minimum duration of the agonist pulse and that the most dominant factor in determining the saccade magnitude is the number of active neurons for the small saccades. For the large saccades, however, the duration of agonist burst firing significantly affects the control of saccades. The proposed saccadic circuitry establishes a complete model of saccade generation since it not only includes the neural circuits at both the premotor and motor stages of the saccade generator, but also uses a time-optimal controller to yield the desired saccade magnitude.

A new linear muscle fiber model for neural control of saccades.

A comprehensive model for the control of horizontal saccades is presented using a new muscle fiber model for the lateral and medial rectus muscles. The importance of this model is that each muscle fiber has a separate neural input. This model is robust and accounts for the neural activity for both large and small saccades. The muscle fiber model consists of serial sequences of muscle fibers in parallel with other serial sequences of muscle fibers. Each muscle fiber is described by a parallel combination of a linear length tension element, viscous element and active state tension generator.

A portable, inexpensive, wireless vital signs monitoring system.

The University of Connecticut, Department of Biomedical Engineering has developed a device to be used by patients to collect physiological data outside of a medical facility. This device facilitates modes of data collection that would be expensive, inconvenient, or impossible to obtain by traditional means within the medical facility. Data can be collected on specific days, at specific times, during specific activities, or while traveling. The device uses biosensors to obtain information such as pulse oximetry (SpO2), heart rate, electrocardiogram (ECG), non-invasive blood pressure (NIBP), and weight which are sent via Bluetooth to an interactive monitoring device. The data can then be downloaded to an electronic storage device or transmitted to a company server, physician's office, or hospital. The data collection software is usable on any computer device with Bluetooth capability, thereby removing the need for special hardware for the monitoring device and reducing the total cost of the system. The modular biosensors can be added or removed as needed without changing the monitoring device software. The user is prompted by easy-to-follow instructions written in non-technical language. Additional features, such as screens with large buttons and large text, allow for use by those with limited vision or limited motor skills.

Linear homeomorphic models for muscles in the head-neck region.

The linear homeomorphic muscle model proposed by Enderle and coworkers for the rectus eye muscle is fitted to reflect the dynamics of muscles in the head-neck complex, specifically in muscles involved in gaze shifts. This parameterization of the model for different muscles in the neck region will serve to drive a 3D dynamic computer model for the movement of the head-neck complex, including bony structures and soft tissues, and aimed to study the neural control of the complex during fast eye and head movements such as saccades and gaze shifts. Parameter values for the different muscles in the neck region were obtained by optimization using simulated annealing. These linear homeomorphic muscle models provide non-linear force-velocity profiles and linear length tension profiles, which are in agreement with results from the more complex Virtual Muscle model, which is based on Zajac's non-linear muscle model.

The DaVinci Group: a second modern Ophthalmotrope.

A group of undergraduate students at the University of Connecticut Biomedical Engineering Program has formed a "club" in order to more fully understand and educate themselves in modeling anatomical processes. This group is called the DaVinci Robot or DaVinci Group. Experiments to mechanically model the six extraocular muscles of the eye have been performed, each meeting little success. While researching methods that would lead to better success, the concept of the Ophthalmotrope was discovered. The Ophthalmotrope is a mechanical visual aide used in teaching the function of the extraocular muscles, prevalent in the mid 1800's. The Group decided to study this device and ultimately decided to build one. The paper presented here discusses our third experiment, currently under investigation, that is, to build an Opthalmotrope. Difficulties with this task are lack of any information with regard to how to construct this device. Presented are descriptions of the Group's initial experiments and research conducted into the construction of the Ophthalmotrpe. In the main body of the presented paper is a description of how the DaVinci Group Ophthalmotrope is constructed. Concluding is a discussion of the progress of the construction of the Ophthalmotrope along with a brief listing of research conducted in order to build the device.

3D dynamic computer model of the head-neck complex.

A 3D dynamic computer model for the movement of the head is presented that incorporates anatomically correct information about the diverse elements forming the system. The skeleton is considered as a set of interconnected rigid 3D bodies following the Newton-Euler laws of movement. The muscles are modeled using Enderle's linear model. Finally, the soft tissues, namely the ligaments, intervertebral disks, and zigapophysial joints, are modeled using the finite elements approach. The model is intended to study the neural network that controls movement and maintains the balance of the head-neck complex during eye movements.

Infra-red radiant intensity exposure safety study for the Eye Tracker.

With any device that is used to record or evaluate biosignals, it is in the inventor's interest to determine how that device withstands a rigorous examination in regards to its inherent safety during use. For this, a Risk Management (Hazard) Analysis is a useful exercise. With this in mind, the most probable hazard concerning the Eye Tracker System (a device used to measure saccadic eye movements utilizing Reflective Differencing of Infra-Red light) is the exposure effect to the human eye caused by the Radiant Intensity of the IR emitters mounted on the Head Mounted Transducer. Presented in this article are the results of a study used to determine the Radiant Intensity exposure of the Eye Tracker as designed. Comparing these results with accepted norms for Radiant Intensity exposure, a redesign of the Head Mounted Transducer is detailed with results given showing that this new transducer fits safely into the accepted norms of Radiant Intensity exposure. Presented are the mathematical calculations used for the initial study and the redesign.

Eye movement detector calibration device.

Presented is a device developed for specifically calibrating and validating the operation of Eye Movement Detectors or Monitors. The Calibrator centers on two one inch diameter HPDE spheres representing the eyes. A Laser Module is embedded in the rear of each sphere emitting a beam against a target divided in equal measurement intervals mounted as part of the device. The device moves the "eyes" about its center axes enabling the user to validate any vertical, horizontal, or X-Y combination eye position in a plus or minus fifteen degree range. Although hand controlled, the Calibrator can be motorized with stepper motors or other desired drivers. Anatomically correct sized pupils are imbedded in the front of each "eye," thereby acting as the target for whichever system is under test by the very portable Calibrator. Currently, a simple battery controlled circuit controls the laser modules and other electric requirements with accommodation for additional circuit components if required in the future. Specifically designed for validating the operation of an IR Reflective Differencing Saccadic Eye Movement Measurement System, the Calibrator can also be used with little or no alteration for validation of camera systems and other types of devices.

The University of Connecticut Biomedical Engineering Mentoring Program for high school students.

For the past four years, the Biomedical Engineering Program at the University of Connecticut has offered a summer mentoring program for high school students interested in biomedical engineering. To offer this program, we have partnered with the UConn Mentor Connection Program, the School of Engineering 2000 Program and the College of Liberal Arts and Sciences Summer Laboratory Apprentice Program. We typically have approximately 20-25 high school students learning about biomedical engineering each summer. The mentoring aspect of the program exists at many different levels, with the graduate students mentoring the undergraduate students, and these students mentoring the high school students. The program starts with a three-hour lecture on biomedical engineering to properly orient the students. An in-depth paper on an area in biomedical engineering is a required component, as well as a PowerPoint presentation on their research. All of the students build a device to record an EKG on a computer using LabView, including signal processing to remove noise. The students learn some rudimentary concepts on electrocardiography and the physiology and anatomy of the heart. The students also learn basic electronics and breadboarding circuits, PSpice, the building of a printed circuit board, PIC microcontroller, the operation of Multimeters (including the oscilloscope), soldering, assembly of the EKG device and writing LabView code to run their device on a PC. The students keep their EKG device, LabView program and a fully illustrated booklet on EKG to bring home with them, and hopefully bring back to their high school to share their experiences with other students and teachers. The students also work on several other projects during this summer experience as well as visit Hartford Hospital to learn about Clinical Engineering.

Porting GENESIS to SIMULINK.

This paper describes the porting of the general simulation system (GENESIS) to Matrix Language Laboratory language (MatLab) SIMULINK, based in the cable theory to simulate the behavior of neurons. A graphic programming approach serves as ideal platform for teaching physiological modeling and neuroengineering courses. The ultimate goal of this project is to integrate all of the chemical, electrical, material, mechanical and neural interactions into a single model that can be viewed seamlessly from a molecular model to the large scale model. Integration of all interactions is not possible with GENESIS, but can be accomplished with SIMULINK.

Dynamic modeling of the neck muscles during horizontal head movement. Part II: Model construction in Pro/Engineer.

This paper describes the next phase of research on a parametric model of the head-neck system for dynamic simulation of horizontal head rotation. A skull has been imported into Pro/Engineer software and has been assigned mass properties such as density, surface area and moments of inertia. The origin of a universal coordinate system has been located at the center of gravity of the T1 vertebrae. Identification of this origin allows insertion and attachment points of the sternocleidomastoid (SCOM) and splenius capitis to be located. An assembly has been created, marking the location of both muscle sets. This paper will also explore the obstacles encountered when working with an imported feature in Pro/E and attempts to resolve some of these issues. The goal of this work involves the creation of a 3D homeomorphic saccadic eye and head movement system.

Knowledge management system for benchmarking performance indicators using statistical process control (SPC) and Virtual Instrumentation (VI).

Healthcare is ever changing environment and with the Joint Commission for the Accreditation of Hospital Organization (JCAHO) emphasis on quality improvement during the past several years, and the cost-focused healthcare reforms of the 1990s, benchmarking with peer comparison, and more recently benchmarking against competitors, has taken on a new emphasis. All acute healthcare organizations accredited by JCAHO now require participation in a program titled ORYX, which is designed to use comparisons with other organizations and promote national benchmarks. The knowledge management system designed assists clinical engineering department to convert vast amounts of available data into information, which is ultimately transformed into knowledge to enable better decision-making. The systems assist in using the data as a comparison tool, to compare the performance internally and also compare performance with peer organizations using the same measures within the same measurement system. Collectively, these applications support better, faster data-driven decisions. This tool provides fast and easy access to financial and quality metrics to clinical engineering department managers, which increases their ability to perform sophisticated analysis to develop accurate models and forecasts, and make timely, data driven decisions. The project also provides a platform by means of which clinical engineering departmental procedures, data, and methods can be assessed and shared among institutions.

The Eye Tracker System--a system to measure and record saccadic eye movements.

The Eye Tracker System, built at the University of Connecticut at Storrs in the Biomedical Instrumentation Lab, consists of three separate and distinct units brought together as a whole system to measure saccades. A seven row, eleven columned array of LEDs mounted on five degree centers along a concave surface provides targeting for the Eye Tracker System wherein the subject eye follows a pattern of illuminated LEDs as determined by the experimenter. The target system is digitally driven by serial inputs from the Main Command System. Subject positioning is aided by the concave surface of the Target System. The System Console employs a multiple regression Operating System to predict Eye Position. Twenty-four channels utilizing the theory of Infrared Light Reflective Differentiation make measurements of the location of the eye. These optoelectronics are mounted in a specialized head-mounted transducer. The optoelectronics are mounted on the interior of a parabolic surface automatically aiming them towards the limbus. The transducer is styled after an ophthalmologist's test frames and is comfortably worn and adjustable in size to fit any subject. The Main Command System authored under G programming language (LabView) provides a graphic user interface (GUI) that controls the generation of the target pattern. The Main Command System also coordinates the programs that acquire all data, the regression algorithm for the real-time prediction of the eye position and the initial calibration of the system. In addition the application is able to save a retrieve data for further analysis.

The operating version of the Eye Tracker, a system to measure saccadic eye movements.

The operating version of the Eye Tracker, a transducer and system using a technique to bounce infrared light off the eye to measure saccadic eye movements in any X-Y position is presented in this paper. Discussed is the method of reading and analyzing eye movement data using a 24-channel infrared optoelectronic array and computer algorithms that utilize a linear regression model to interpret and determine eye location, the 24-channels used to ensure accurate reading of eye position. Accuracy is also maintained by a signal processing system that attenuates incident light as well as ambient light. Also discussed is a novel method of mounting the infrared array on hemispherical shaped eyepieces that in turn are mounted on goggles styled after an ophthalmologist's test frames that is comfortably worn and adjustable in size to fit any subject. A computer controlled, wall mounted light bank facilitates targeting for eye movements. The Eye Tracker is built to meet standards of a professional medical device manufacturer following typical mechanical, electrical, and safety techniques unique to device packaging.