Analysis of a distributed model of leg coordination. I. Individual coordination mechanisms.

Using tools from discrete dynamical systems theory, we begin a systematic analysis of a distributed model of leg coordination with both biological and robotic applications. In this paper, we clarify the role of individual coordination mechanisms by studying a system of two leg oscillators coupled in one direction by each of the three major mechanisms that have been described for the stick insect Carausius morosus. For each mechanism, we derive analytical return maps, and analyze the behavior of these return maps under iteration in order to determine the asymptotic phase relationship between the two legs. We also derive asymptotic relative phase densities for each mechanism and compare these densities to those obtained from numerical simulations of the model. Our analysis demonstrates that, although each of these mechanisms can individually compress a range of initial conditions into a narrow band of relative phase, this asymptotic relative phase relationship is, in general, only neutrally stable. We also show that the nonlinear dependence of relative phase on walking speed along the body in the full hexapod model can be explained by our analysis. Finally, we provide detailed parameter charts of the range of behavior that each mechanism can produce as coupling strength and walking speed are varied.

Elders using a community network: profile of a champion.

Computer networks serve as convenient, efficient, and enduring vehicles for delivering nursing services to patients at home. The ComputerLink, a nurse-supervised computer network, provides information, decision support, and communication services to caregivers of people with Alzheimer's Disease [1]. The data obtained in the original experiment included daily logs of each caregiver's use of ComputerLink (n=606 days), records of each caregiver's ComputerLink access behavior (47 subjects; 3875 accesses), and transcripts of the public communications (n=749) posted on the ComputerLink's open electronic bulletin board. In this paper, we present a case study of an early user's pattern of connections to ComputerLink as an atypical example of how elders make use of computer networks.

ComputerLink: the impact of a computer network on Alzheimer's caregivers' decision-making confidence and skill.

1. INTRODUCTION. Decision-making demands faced by homebound caregivers of persons with Alzheimer's Disease (AD) are numerous and complex. Although caregivers frequently know what to do in caring for the person with AD, they lack confidence in their decisions [1]. The challenge of caregiving decisions may be compounded by the lack of resources to aid in decision-making or affirm decisions made. Because many caregivers are homebound, they are unable to avail themselves of traditional health and social services. ComputerLink, computer network, was designed to address the needs of these homebound caregivers. 2. DESCRIPTION. The ComputerLink consisted of a set of specialized programs and utilities residing within a public computer network. The three main features of the ComputerLink, which may provide aid to caregivers in decision making, include: the electronic encyclopedia (EE); a communications utility composed of a question and answer bulletin board (Q&A) and public (Forum) and private mail services; and a decision support module (DSM). The EE contained illness-specific information to support decision-making. The Forum and private mail provided caregivers with a means to interact with peers and professionals about their caregiving decisions. Q&A provided the opportunity to ask questions about caregiving and receive feedback from professionals and peers. The DSM could be accessed to gain information about decision-making or to actually work through a decision problem. The DSM was built on a multi-attribute utility model which employed English-language questions to guide users through a decision analysis. The analysis strategy was designed to help the user focus on the values and trade-offs that occur during difficult choices. The impact of ComputerLink on decision confidence and skill was evaluated as part of a larger randomized experiment. 102 AD caregivers were recruited: 51 caregivers in the control group and 47 in the experimental group completed the 12-month study. The mean age of the caregivers was 60 years. Thirty-three percent were male and 28 percent were Black. The groups did not differ in demographic characteristics. The ComputerLink interface was menu-driven and the system was available 24 hours. ComputerLink use was captured through a passive monitoring system. AD caregivers accessed ComputerLink a total of 3,875 times, with a mean access per individual of 83 (range: 3 - 590). The mean length of an encounter was 13 minutes; subjects typically accessed two or more functions during this time. The decision support model was accessed 91 times. The communication functions were most frequently used (3,724 Forum accesses and 1,888 private mail); the information utility was accessed 518 times. 3. RESULTS. Decision confidence was objectively measured using a modification of the Saunders and Courtney confidence-in-decision making instrument. Caregivers who had access to ComputerLink experienced greater confidence in decision-making than caregivers in the control group (t = 2.73, p < .01). Access to ComputerLink did not alter decision skill as measured by the number of alternative solutions generated for two self-identified decisions problems (t = .18, p < .05). Decision-making confidence correlated positively with ComputerLink accesses (r = .32, p = < .02) and with length of time spent on ComputerLink (r = .30, p = < .02). 56% of the AD caregivers reported that use of ComputerLink increased both their confidence and skill in decision making, though only 38 percent reported using the DSM to make a decision. 4. DISCUSSION. Access to ComputerLink increased decision-making confidence, but not decision-making skill in AD caregivers. The impact of ComputerLink on decision confidence, and not skill, may be related to the differential use of the utilities. (abstract truncated)