[ Aleph One home page | Company Information | Order form | Security Privacy and Terms of sale | Search ]

Computer-Enhanced Biofeedback

The introduction of a microcomputer into a Biofeedback system opens up a number of attractive possibilities such as:

Providing graphical or visual or analog feedback
Enhancing feedback with sound and colour
Providing feedback of the ratio or the difference, of two signals, or of more complex functions
Maintaining records of performance and printing out results
Adapting feedback to the particular needs of one patient at a time.

Such systems will be of value to physiotherapists, occupational therapists and all those dealing with cases of physical handicap; feedback of muscle tension has been shown to be of value in cases as diverse as cerebral palsy, stroke and traumatic injury.

In each type of case there is some redundant or unutilised capacity in the nervous system, which can be brought into use and developed if suitable feedback is available.

The value of electronic feedback of muscle tension is that it makes the patient aware of levels of tension too low to show movement or to be palpable, so that even an apparently paralysed patient can recover some muscle action and control. Some of the types of feedback available are particularly easy to assimilate and require very little cognitive capacity in the user.

Two types of system are offered, both using Acorn computers. They share the same hardware, but use different software. Neither requires any knowledge of a programming language.

The older system requires a BBC Master computer; this has been sold since 1984. To use the system you answer a series of questions. Prompts of likely answers, and default values, are provided.

Another version is for Acorn Archimedes and Risc PC computers, which takes advantage of the graphical user interface. Rather than answering questions, the mouse is used to push buttons to make selections. This system is so intuitive and simple that it is easy to get it working without reading the instruction book provided.

Software

In each case the software is constantly evolving, often by the addition of programs which existing users have found valuable and added to the common pool. Updates are provided free. For these reasons the descriptions of software which follow are only general; revisions will be made when a new need is defined or a creative addition occurs. If you have a particular need which is not covered discuss it with us. If we feel it will be of general interest we may create or amend a program to include it.

The main form of presentation is graphs showing how signals change with time. They may show two muscle tensions, or one muscle tension and a Skin Conductance trace (a measure of general autonomic arousal). The speed at which the trace moves across the screen can be varied widely to accommodate rapidly-changing signals from small muscles, perhaps in the hands, or the gradual drop in arousal in an initially very tense person relaxes.

BBC Master software

For BBC Master computers a large number of games is available, with action controlled by muscle tension. Both young people and adults find these games highly motivating and entertaining, and as they can be tailored at the time of use to require a particular level of action from a particular muscle group, they provide a powerful tool for exercising and training muscles.

Other programs provide functions such as:

Integrated or Averaged signals, or other derived functions such as Time Above Threshold, or Peak Tension, presented on the screen or on paper
Activation or switches by specified levels of tension, to operate games, environmental controls, communication aids, toys, music and so on
Timed cues to perform exercises, with recording and printing of results obtained
Display of (EEG) Electro-Cardio-Graph signal, and Heart Rate calculated from inter-beat intervals
Patient record-keeping and review and print-out
Switching action(s) when muscle tensions exceed a specified fraction of the levels attainable by that user on that occasion.

A copy of the Instruction Book is available free on request.

Acorn RISC computer software

For Acorn RISC computers including the Archimedes, the A3000 and the Risc PC, the emphasis is on presenting graphs of changes over time.

However, control is by means of control panels and the mouse. This is used to select one or two traces, labels for the axes, Relaxometer or Muscle Tension, speed across the screen, sensitivity and so on, by clicking on the relevant switches.

The data shown on screen can be printed and saved to disc, to make a permanent record of a patient's performance on a particular occasion and to enable review at a later date.

Specification

Both systems share the Myolink myo-electric amplifier. This is a small rugged metal case with no controls and a cable to the User Port of the computer. Surface electrodes connect to sockets on the case, which receives power from the computer through an isolating power supply. The signals are translated into a pulse train which is passed back to the computer via an optical isolator, to ensure complete electrical safety.

The Myolink connects to a User Port socket, located under the keyboard in BBC Master computers. Acorn RISC computers require a User Port Expansion Card. These are available from us or from Acorn dealers.

Software and hardware are not available separately. Our software is not protected, and users are welcome to adapt it to their own needs. Software for the BBC/Master is supplied on a 5.25in floppy disc with 80 tracks, in DFS format, with a Menu to facilitate choice of the required program. It automatically detects what model of computer is in use, and adapts the screen mode accordingly. Keeping patient records on disc requires a second disc drive.

Software for Acorn RISC computers is supplied on 3.5in floppy disc.

In each case surface electrodes and a choice of electrode cables are provided.

The Myolink Amplifier has an input impedance over 1 million million ohms, input noise under 1 microvolt RMS, and a CMRR well over 100dB. Its bandwidth is 35 to 350Hz, with a mains frequency notch filter at least 40dB deep. It is sensitive from 1 to over 500 microvolts, and draws about 120mA at 5V from the computer. The output comprises two pulse trains of 20 KHz to over 500 KHz, multiplexed under software control, with frequencies proportional to the input signal amplitudes. The amplifier has a time constant of about 0.3s.

The Myolink amplifier measures 150 x 90 x 35mm and weighs 500g.

An auxiliary socket can accept a signal from another voltage source such as our Model Q Relaxometer, a self-contained Skin Conductance instrument with an output socket.

Related products

For simple single-channel instruments, not involving computers, see Myo-electric Instruments. See Relaxometers for a more detailed description of the Relaxometer.

The Myolink is also a part of our MYOLOG portable system for collecting and logging data on a freely-moving person and later passing it to a computer for analysis. See Data Sheet 13, Ambulatory Physiological Recording.

For details of prices and how to order these products please see our current price list.

Relaxometer® is a Registered Trade Mark of Aleph One Ltd.

Last Updated: 2000.10.20

[ Aleph One home page | Company Information | Order Form | Security Privacy and Terms of sale | Search ]