What do I need for EEG measurement or neurofeedback?
We are often asked for a quote for "Everything I need for a neurofeedback system?". This is a difficult question to answer concisely without knowing more about the present and future scope of the client's application. Like most things in life - if you want a better answer, first you need to ask a better question.
We deal with the NeXus systems for biofeedback and physiological monitoring and these are excellent products but they are not going to be perfect for everyone. If we don't know anything about your true requirement it means we are going to be wasting your time telling you about things that are not going to be of interest.
The way we can approach this more systematically is by thinking about the fundamental building blocks of a potential system and looking at the consequences of particular choices.
Like any building we should start with the foundations which in this case is your particular application. If you are a clinician interested in working with neurofeedback on a budget you might be perfectly well served by choosing a NeXus 4 (2 channel) system. If you want to carry out multimodal stress testing in your practice perhaps the NeXus 10 would be a better option as this allows you to use a wider range of sensors.
On the other hand, if you are based in a University research unit wanting a high performance, broad capability system maybe the NeXus 32 (24 channels) is going to be a better bet.
So thinking carefully about your intended application largely determines what you will need in terms of the hardware.
Once you have thought through your application, the next level above is the choice of System and Software. It may be that the NeXus range fits the bill - or maybe it won't - but it makes sense only to consider the system and software and everything else above (sensors, electrodes etc) when you are clear about your application. In the NeXus range there are three fundamental choices
- NeXus-4 - A 2 channel system - base price around £2,400 ex VAT
- NeXus-10 MkII - A 10 channel system - base price around £4,200 ex VAT
- NeXus-32 - A 32 channel system - base price around £14,200 ex VAT
These system prices are correct at the time of writing but subject to change. There is an obvious difference in the prices of the three systems. This is not a reflection of the quality of the hardware but it is a reflection of the number of input channels and the breadth of performance of these units. We have a comparison table which is worth looking at if you want to see how the three NeXus units stack up.
If your interest is purely EEG you will note that the NeXus 4 offers 2 channels, the NeXus 10 offers 4 channels and so does the NeXus 32. Look more closely and you will note that the NeXus 32 offers full qEEG (full cap EEG) capability. This is way beyond what you would need for routine EEG biofeedback (neurofeedback). The NeXus 4 is more than capable of being at the heart of your neurofeedback system. What you add as you move up the range are more channels and the ability to collect data from multiple sensors at the same time. We will return to think about what sensors are needed in a moment.
Each NeXus unit is provided with an appropriate version of the BioTrace+ software. Whatever the brand of hardware you choose, it is very important to know how well the control software functions. The BioTrace+ software is the "conductor" to the hardware's "orchestra" - it's the thing that makes everything fit together. The software is designed to allow you to concentrate on your application and a bit less on the technicalities. A lot of protocols and and screens have been included in the software but you have the ability to create your own custom screens and protocols if necessary. Having said that the units are easy to use, it is important still In my view ot have a grasp of the fundamentals of instrumentation and measurement. Things are close to being "plug and play" these days but it is still possible to get things wrong. You will find a descirption of what BioTrace+ can do at this page.
Once we have narrowed down the System and Software which is most suitable for your application we can think about the next layer up - the Sensors you need follwed by the Electrodes, Gels and other accessories.
Let's just consider the simplest choice for getting going with neurofeedback.
The simplest route to getting going with Neurofeedback is to choose an EXG Sensor or a EXG Sensor TP (Touch Proof). These are about £314 (ex VAT) at the time of writing. As you might guess, the EXG sensor can be used in a number of ways - for example, for EMG or ECG measurement if paired with the correct electrodes.
For neurofeedback, the EXG Sensor is typically paired with some EEG Disc electrodes and NuPrep with Ten20 for skin preparation. The only other essential component needed is then an EXG Ground cable which is always required for good signal fidelity.
Alternatively you could choose to pair the EXG sensor TP with the EEG minicap electrodes and the MInicap or microcap itself. The minicap/microcap structures can help with positioning the EEG electrodes which could be used with some electrogel for a good contact.
If you are involved in neurofeedback it's possible you might be interested in the NeXus SCP sensor. This sensor has been specially designed for measuring Slow Cortical Potentials which are signals in the low frequency range of the EEG spectrum (below 1 Hz). This is a fascinating area and one worthy of an article in itself. The NeXus systems are designed with the characteristics to support these low frequency signals - not all biofeedback systems can do this.
In this article I have tried to give a structure which at least might help ask the right questions to get good advice and a rational quote. It always make sense to start with the foundation of the specification which is the intended application. This automatically will suggest the ideal NeXus system to use. The choice of sensor, electrode and accessories can then b eeasily made.