A Two-Dimensional Visual Tracking Array

The density and concurrency available in VLSI make it an excellent technology for implementing visual image-processing. By incorporating phototransistors and analog processing elements onto a single die, the large signal bandwidths required for real-time computations can be achieved. This paper describes a VLSI chip that computes the "center of intensity" of a two-dimensional visual field. One application for this network is the localization of a bright spot of light against a dark background. Theoretical and experimental results are presented to describe the operation of the system and its suitability as a input device for tracking servo systems

An Analog VLSI Model of Adaptation in the Vestibulo-Ocular Reflex

The vestibulo-ocular reflex (VOR) is the primary mechanism that controls the compensatory eye movements that stabilize retinal images during rapid head motion. The primary pathways of this system are feed-forward, with inputs from the semicircular canals and outputs to the oculomotor system. Since visual feedback is not used directly in the VOR computation, the system must exploit motor learning to perform correctly. Lisberger(1988) has proposed a model for adapting the VOR gain using image-slip information from the retina. We have designed and tested analog very large-scale integrated (VLSI) circuitry that implements a simplified version of Lisberger's adaptive VOR model

Implementing neural architectures using analog VLSI circuits

Analog very large-scale integrated (VLSI) technology can be used not only to study and simulate biological systems, but also to emulate them in designing artificial sensory systems. A methodology for building these systems in CMOS VLSI technology has been developed using analog micropower circuit elements that can be hierarchically combined. Using this methodology, experimental VLSI chips of visual and motor subsystems have been designed and fabricated. These chips exhibit behavior similar to that of biological systems, and perform computations useful for artificial sensory systems

A Prototype of a Neural, Powered, Transtibial Prosthesis for the Cat: Benchtop Characterization

We developed a prototype of a neural, powered, transtibial prosthesis for the use in a feline model of prosthetic gait. The prosthesis was designed for attachment to a percutaneous porous titanium implant integrated with bone, skin, and residual nerves and muscles. In the benchtop testing, the prosthesis was fixed in a testing rig and subjected to rhythmic vertical displacements and interactions with the ground at a cadence corresponding to cat walking. Several prosthesis functions were evaluated. They included sensing ground contact, control of transitions between the finite states of prosthesis loading, and a closed-loop modulation of the linear actuator gain in each loading cycle. The prosthetic design parameters (prosthesis length = 55 mm, mass = 63 g, peak extension moment = 1 Nm) corresponded closely to those of the cat foot-ankle with distal shank and the peak ankle extension moment during level walking. The linear actuator operated the prosthetic ankle joint using inputs emulating myoelectric activity of residual muscles. The linear actuator gain was modulated in each cycle to minimize the difference between the peak of ground reaction forces (GRF) recorded by a ground force sensor and a target force value. The benchtop test results demonstrated a close agreement between the GRF peaks and patterns produced by the prosthesis and by cats during level walking

GENDER DIFFERENCES IN AWARENESS OF COURTSHIP INITIATION TACTICS

In this study, two phases of the initiation of courtship behavior are distinguished, namely the first move of making the contact, and the self-presentation after the contact has been established. Gender differences with respect to cognitions and expectations of courtship behavior were analyzed through self-report in a Dutch Caucasian student population. Our goal was to assess male and female roles in these two phases, and to relate the findings to hypothesized gender role changes. It appeared that both men and women were apparently unaware of which gender usually initiates courtship. Furthermore, both genders reported eye contact as the most frequently used initiation tactic. However the genders differed in other tactics, women reporting the use of indirect nonverbal tactics more often than men, and men reporting their engagement in direct verbal ones more often than women. In presenting themselves, men stressed personal characteristics that are traditionally interpreted as female-valued (such as tenderness) more than women did, whereas women stressed characteristics that are traditionally interpreted as male-valued (such as being prestigiously occupied) more than men did. This apparent change in gender role pattern is discussed against the background of the assumed function of courtship behavior and societal developments

Optimization of Stimulation Parameters for Targeted Activation of Multiple Neurons Using Closed-Loop Search Methods

Differential activation of neuronal populations can improve the efficacy of clinical devices such as sensory or cortical prostheses. Improving stimulus specificity will facilitate targeted neuronal activation to convey biologically realistic percepts. In order to deliver more complex stimuli to a neuronal population, stimulus optimization techniques must be developed that will enable a single electrode to activate subpopulations of neurons. However, determining the stimulus needed to evoke targeted neuronal activity is challenging. To find the most selective waveform for a particular population, we apply an optimization-based search routine, Powell’s conjugate direction method, to systematically search the stimulus waveform space. This routine utilizes a 1-D sigmoid activation model and a 2-D strength–duration curve to measure neuronal activation throughout the stimulus waveform space. We implement our search routine in both an experimental study and a simulation study to characterize potential stimulus-evoked populations and the associated selective stimulus waveform spaces. We found that for a population of five neurons, seven distinct sub-populations could be activated. The stimulus waveform space and evoked neuronal activation curves vary with each new combination of neuronal culture and electrode array, resulting in a unique selectivity space. The method presented here can be used to efficiently uncover the selectivity space, focusing experiments in regions with the desired activation pattern

An analog VLSI model of muscular contraction

© 2003 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksDOI: 10.1109/TCSII.2003.813593We have developed analog VLSI circuits to model the behavior demonstrated by biological sarcomeres, the force generating components of muscle tissue. The circuits are based upon the mathematical description of crossbridge populations developed by A. F. Huxley (1957). We have implemented the sarcomere circuit using a standard 1.2 μm process, and have demonstrated the nonlinear transient behaviors exhibited by biological muscle

A Simple Neuron Servo

This paper describes a simple servo controller build from components having neuronlike features. Experimental results illustrate the properties of the system, and a comparison is made with conventional controllers