An Alpha Detection and Feedback Control System

A system of detecting EEG alpha rhythms and using these to control stimulus displays is described. The detection system parameters are chosen to match the psychological and behavioral processes with the EEG index in the time domain. The feedback control system is designed to control visual and auditory displays, clock and counters, and computer sampling routines, and provide maximum flexibility in experimental design.     

Time-optimal control for robotic manipulators

Optimal control methods present an efficient approach to construct controls of robotic manipulators. Much recent research has been devoted to different problems of optimal control for industrial robots. In this paper we give a brief survey of work done in this field and present some new results on optimization of robotic motions. Manipulation robots governed by electromechanical drives are considered. We obtain open-loop and feedback time-optimal controls for robotic motions using both analytical and numerical methods. The results show that optimal controls can lead to a considerable improvement in the time taken for transport operations performed by robots.     

A microcomputer oxygen control system for ventilatory therapy

A computer-based feedback system has been developed to adjust the concentration of oxygen in the inspired gas of a patient under artificial respiration. The system uses a proportional plus integral controller and feedback of arterial oxygen saturation to adjust the inspired oxygen fraction. The effectiveness of the controller has been tested using a dynamic, mathematical model of the human respiratory system. This relatively sophisticated model has been developed and examined in the past, and it has been shown that it can realistically describe the human respiratory system for a wide variety of test conditions. The performance of the oxygen control system has been evaluated using the simulation model. The response of the controller to different disturbances is always stable, with arterial pressure of oxygen returning to normal in less than 12 minutes. Some of the simulation results are presented to illustrate the dynamic behavior and robustness of the controller.     

Perceptual learning without feedback in non-stationary contexts: data and model

The role of feedback in perceptual learning is probed in an orientation discrimination experiment under destabilizing non-stationary conditions, and explored in a neural-network model. Experimentally, perceptual learning was examined with periodic alteration of a strong external noise context. The speed of learning, the performance loss at each change in external noise context (switch cost), and the asymptotic accuracy d' without feedback were very similar or identical to those with feedback. However, lack of feedback led to higher decision bias (error responses matching the external noise context). In the model, the stimulus representations are constant, whereas the read-out connections to a decision unit learn by a Hebbian plasticity rule that may be augmented by additional feedback input and criterion control of decision bias.     

A portable radiation-force balance for use with diagnostic ultrasonic equipment

It is desirable to be able to measure power output of diagnostic ultrasonic transducers for both technical and biological reasons. Design criteria for an instrument to fulfill this purpose on a routine basis are suggested. Previous approaches are discussed in relation to these criteria and a new instrument design is presented. This is based on a measurement of radiation force using a null system, with a magnetic restoring force controlled by a pair of photo-detectors. The method of calibration is described and a selection of field results obtained with the prototype instrument are presented. Methods for applying the same principal to beam plotting, and modifying the instrument for use with therapy machines are also described.     

The development of a computer assisted instruction and assessment system in pharmacology

We describe the construction of a computer based system for instruction and assessment in pharmacology, utilizing a large bank of multiple choice questions. Items were collected from many sources, edited and coded for student suitability, topic, taxonomy and difficulty and text references. Students reserve a time during the day, specify the type of test desired and questions are presented randomly from the subset satisfying their criteria. Answers are scored after each question and a summary given at the end of every test; details on item performance are recorded automatically. The biggest hurdle in implementation was the assembly, review, classification and editing of items, while the programming was relatively straight-forward. A number of modifications had to be made to the initial plans and changes will undoubtedly continue with further experience. When fully operational the system will possess a number of advantages including: elimination of test preparation, editing and marking; facilitated item review opportunities; increased objectivity, feedback, flexibility and descreased anxiety in students.     

Monitoring force errors: medial-frontal negativity in a unimanual force-production task

The effects of force production on medial-frontal negativity (MFN), reflecting the activity of an internal action-monitoring system, were investigated in a force-production task. A precue indicated a low or high force before a stimulus signaled the execution of the same or opposite force. An incorrectly exerted force was assumed to involve an error of force selection if the opposite force was required (invalid precue), and an error of force execution if the same force was required (valid precue). The task was repeated to examine any improvements in monitoring sensitivity. No force-related effects were observed on MFN amplitude. Although performance improved, there was no evidence of a force-error sensitive monitoring system. As the MFN and motor activity were affected by the precue invalidity regardless of the response outcome, the MFN might reflect the activity of a general action-evaluation system that is indirectly related to motor activation.