Inside the bone, the trabecular system of the spongy bone is observed, which has a complicated mesh-like structure. The configuration and structure of trabeculae are strongly related to the loads acting on the bone. Therefore, the trabecular system gives us useful information about the mechanical environment of the bone. In this study, the trabecular images from X-ray pictures of the bone sliced from the pelvis are analyzed from the viewpoint of the thickness, the density and the direction through an image processing. The processed trabecular lines are reconstructed three-dimensionally by using some rules in order to know three-dimensional flow of the force.
In the series of our papers we have shown by computer simulations that cyclic enzyme systems in metabolic contorol pathways have the reliability of threshold logic function capable of storing short-memory, and the applicability to a prototype of an artificial neuronic device. Mimicking the switching algorithm of cyclic enzyme system based on a set of differential equations, the board-leveled analog circuit of this device is developed by using the PSpice program. We call this device “biochemical neuron”. This kind of study belongs to the practical implementation of functional devices in “natural intelligence” such as metabolic control system and neural networks.
We developed a three-dimensional imaging system using a. two-dimensional ultrasonic array probe. A reconstruction of the three-dimensional image, which needs no ultrasonic scanning, was performed by a transmission of ultrasonic spherical pulse and simultaneous detections of echo signal at some receivers. The experimental results indicate that a 3mm×3mm square hole in a sliced ham, a butter block and the three-dimensional structure in a rabbit heart can be reconstructed by this system.
In this paper, the behavior of fish school is considered as an autonomous decentralized system, that is, each individual fish behaves autonomously while keeping a specific order based on the information from other fish. The model of such a system consists of a propulsive mechanism, an environmental effect and a schooling mechanism. In our earlier papers, it was shown that fish can make a school if each individual in the school gets the information from only a few individuals around him. In this paper, fish behavior is investigated for the cases where the school is affected by various environments, i. e., approach of an enemy, appearance of an obstacle, and so on. Especially, the relation-ship between the fish behavior and the quantity of information is investigated to analyze the state of each individual in the school.
We investigated the effects of a cross-innervation between the serratus nerve and the biceps nerve of turtles on the plasticity of respiratory oscillator in the central nervous system. Biceps muscle activity during locomotion, which was independent from respiratory activity before the cross-innervation, was once synchronized with the respiratory activity one week to one month after the cross-innervation, and then returned to be asynchronous to the respiratory activity. These results suggest that the biceps muscle was once controlled in the rhythm generated in the respiratory oscillator, and then only the part of the respiratory oscillator which corresponds to the biceps muscle, was changed its function to generate a different rhythm from the respiratory rhythm, probably suitable for the locomotion.
The human visual system is a sensory organ having a very high performance. It analyzes various visual information at a very high speed. The key of such performance will be the parallel structure of the visual system. As the fundamental process of the human visual system, the authors pay attention to the achromatic information processing system. In order to elucidate mechanism of the achromatic channel, in the present paper, the achromatic perception has been measured by three psychological experiments. In the first experiment, the spatial characteristic of the achromatic perception has been measured for six wavelengths of monochromatic light. In the second experiment, the relative spectral sensitivity of the achromatic perception has been measured for two test sizes. In the third experiment, the relative spectral sensitivity of the achromatic perception has been measured for two background levels, i.e., at 55 and 798 Td. It is difficult to explain the experimental results by the conventional achromatic channel model, and the experimental results suggest that the achromatic information is processed by several subsystems in parallel. In order to explain the experimental results, we propose a model of achromatic information processing composed of five stages and three subsystems.
It has been reported that after prolonged starvation, bacterial cells increase in the frequency of mutation and produce new advantageous phenotypes. This result gives a suggestion for the improvement of the genetic algorithm for optimization problems. The stochastic automaton is applied for the learning of the position of loci at chromosome so that the evaluation takes a higher value. The state stochastic vector of the automaton thus obtained generates a mutation rate for corresponding locus of the chromosome. This procedure helps the algorithm to escape from the trapping in local minima. The effectiveness is shown especially for the maximum search problem of a variable-separable multi-peak function.
Bionic systems are artifical systems which have the “type” of biological systems. This paper describes conception of bionic systems and a methodology to develop these new systems.After the procedure of the metaphor from biological world to artificial world is indicated, a metaphorical model for the artificial systems is constructed as a metaphor of the biological systems.Models of the bionic systems, i. e., metaphorical models of artificial systems have the following special features; (1) Set structure which consists of autonomous modeling elements. (2) Set of Input/Output functions which constructs the modeling element. (3) Existence of cyclic loops which are obtained by Input/Output chain. (4) Automatic decision making of the systems which is based on stability of the cyclic loops. (5) Self-organization for system design and system control.
An adaptation mechanism is proposed for the Neural Integrator (NI) of the eye movement system. The NI model has a bilateral structure with the commissural inhibitory connections, and the adaptation mechanism is based on the function of the bilateral structure. The adaptation mechanism gives the NI model a large time constant and adjusts its resting balance. Retinal-image slip signals are used as error signals. The NI connections are assumed to be separated into two classes based on their discharge type. According to the direction of the retinal slip, they are modified reciprocally : the NI connection weights of one class are modified more while those of the other class are modified less. The connection weights in each class are directly modified by using retinal slip signals without any complex calculations. The relationship between the NI adaptation mechanism and that of the pulse and step components was analyzed, and the different adaptation rates were introduced to make the NI adaptation robust. Fast adaptation rates were given to the pulse and step components, and a slow rate was given to the NI. The ability of the proposed adaptation mechanism was tested by the simulation.
Bone remodels its structural shape adapting to the mechanical environment, and some optimality has been speculated at the adapted state. This article exerts the mathematical model of bone remodeling reported previously in generating an appropriate structural shape under the specified mechanical condition. The density of the internal structure and the initial strain in the lattice continuum are altered iteratively by referring to the nonuniformity of effective stress. The basic characteristics of the proposed idea are examined with a simple tensioned structure by finite element simulation. Case studies are conducted for rectangular blocks with different conditions, and the structural geometry and/or topology is resulted corresponding to the individual mechanical condition. It is demonstrated that the adaptation model of living bone has the capability to suggest the structural geometry and topology as the framed and/or composite structure having mechanical anisotropy, nonuniform density and residual strain.
From the viewpoint of computational theory, we discuss the visuomotor transformation in human grasping movements. Determining a hand shape to grasp an object is an ill-posed problem, because there are many ways to grasp the object. We propose two kinds of neural network architectures for calculating the optimal hand shape. Network operation is divided into a learning phase and an optimization phase. In the learning phase, an internal model that represents the relation between objects and hand shapes is acquired. In the optimization phase, the most suitable hand shapes for grasping objects are designed by using a relaxation computation of the network. In the first model, the internal representations of objects are specified with symbolic or population coding. In the second model, no representation of objects is defined beforehand; instead, the neural network acquires the internal representations of objects by integrating visual and motor information.
Responses of the Nagumo neural circuit to nonperiodic pulse-train stimulation are studied in detail. In particular, using the input pulses with the 1/f-like fluctuation, we show the global firing structure. To try to clarify the role of the 1/f fluctuation in the neural information processing, we investigate the histogram of the neuron-response interval, the power spectral density for neuron responses, and the return map of the membrane potential. As numerical results, it is shown that the almost same global firing pattern structure as one for periodic pulse stimulations. Four observations, furthermore, are obtained as follows : (1) there are three kinds of characteristic spectrals of neuron responses, (2) all responses for the 1/fn spectral inputs in the single-response region have the 1/f2-like spectral, (3) characteristics of neuron responses are independent of the fluctuation- width of inputs, and (4) in the non 1/f random spectral inputs, the response spectral has the almost exponential type.