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At least 397 records · Page 22Linked to original sources
PubMed1998

Analog versus digital: extrapolating from electronics to neurobiology.

We review the pros and cons of analog and digital computation. We propose that computation that is most efficient in its use of resources is neither analog computation nor digital computation but, rather, a mixture of the two forms. For maximum efficiency, the information and information-processing resources of the hybrid form must be distributed over many wires, with an optimal signal-to-noise ratio per wire. Our results suggest that it is likely that the brain computes in a hybrid fashion and that an underappreciated and important reason for the efficiency of the human brain, which consumes only 12 W, is the hybrid and distributed nature of its architecture.

Artifacts↗
PubMed2000

On the computational complexity of binary and analog symmetric hopfield nets

We investigate the computational properties of finite binary- and analog-state discrete-time symmetric Hopfield nets. For binary networks, we obtain a simulation of convergent asymmetric networks by symmetric networks with only a linear increase in network size and computation time. Then we analyze the convergence time of Hopfield nets in terms of the length of their bit representations. Here we construct an analog symmetric network whose convergence time exceeds the convergence time of any binary Hopfield net with the same representation length. Further, we prove that the MIN ENERGY problem for analog Hopfield nets is NP-hard and provide a polynomial time approximation algorithm for this problem in the case of binary nets. Finally, we show that symmetric analog nets with an external clock are computationally Turing universal.

Journal Article↗
PubMed1969

An introduction to hybrid computers and their application to optimization problems.

The author, who is Secretary of the Analog Section of the British Computer Society, describes the way in which some of the logic components of a parallel logic analog computer function, and goes on to discuss the use of such a computer in optimization problems, as for instance in finding the best estimates of the parameters on compartmentation analysis of isotopic tracer experiments. The increased power which is gained when an analog computer is coupled to (hybridized with) a general purpose digital computer is then discussed, as shown for example in the increased speed of random-search optimization techniques when an analog computer is used to integrate the differential equations, or the improvement in steepest ascent methods when the parallel logic can be used to keep the hill-climb path continuously on the line of steepest ascent. Finally, the use of a hybrid computer in solving partial differential equations is briefly outlined.

Journal Article↗
PubMed2003

ACE16k: a 128x128 focal plane analog processor with digital I/O.

This paper presents a new generation 128x128 Focal-Plane Analog Programmable Array Processor -FPAPAP, from a system level perspective. It has been manufactured in a 0.35 microm standard digital 1P-5M CMOS technology. It has been designed to achieve the high-speed and moderate-accuracy -8b- requirements of most real time -early-vision applications. External data interchange and control are completely digital. The chip contains close to four million transistors, 90% of them working in analog mode. It achieves peak computing values of 0.33TeraOPS while keeping power consumption at reasonable limits -82.5GOPS/W. Preliminary experimental results are also provided in the paper.

Computers, Analog↗
PubMed1997

Analog circuit for real-time computation of respiratory mechanical impedance in sleep studies.

The aim of this work was to develop a low-cost circuit for real-time analog computation of the respiratory mechanical impedance in sleep studies. The practical performance of the circuit was tested in six patients with obstructive sleep apnea. The impedance signal provided by the analog circuit was compared with the impedance calculated simultaneously with a conventional computerized system. We concluded that the low-cost analog circuit developed could be a useful tool for facilitating the real-time assessment of airway obstruction in routine sleep studies.

Airway Resistance↗
PubMed1980

Adrenal scintigraphy: comparison of the Anger tomoigraphic scanner and the large-field gamma camera: concise communication.

To evaluate observer performance in adrenal scintigraphy with two different imaging instruments and to assess the requirement for computer processing in routine adrenal imaging, gamma-camera images (analog and computer processed) and Anger tomoscanner studies were independently interpreted by three observers. Thirty-eight pairs of images were used for the analysis of the receiver operating characteristic (ROC) curve in comparing the tomoscanner with the large-field gamma camera, and 44 pairs of images were used for the comparison of the gamma camera analog images with computer-processed images. ROC analysis demonstrated a higher detection rate for the tomographic images. The computer-processed images did not improve adrenal detection. When each case was considered individually, the tomoiscanner was preferred in 37% of cases, and in 50% of cases, both instruments were considered to be equaly valuable.

Adolescent↗