The Future of High-Density Neurophysiology Recordings
Over the last decade, neuroscience researchers working in the field of in vivo electrophysiology have gradually moved from using predominantly analog systems to digital alternatives. The development of new digital technology has allowed for the processing and analysis of larger data-sets at a lower cost. As a result, more research labs have been able to access “high-density” digital systems. Depending on the lab and research question, high-density electrophysiology systems are usually more desirable due to their capacity to record from more channels, resulting in more neural data for the researcher. High-density systems allow for single-neuron resolution studies, and they also allow for the studies of different neural circuits within and between different regions of the brain.
Understanding Analog and Digital Signals in Neuroscience
In simple terms, an analog signal is any continuous signal that varies over time. Within the field of in vivo electrophysiology, the electrical activity produced by the brain is an analog signal that can be recorded as a measure of brain activity. A digital signal, on the other hand, is a signal that is made up of discrete data points streamed at regular intervals (e.g. binary signals). In order for researchers to visualize brain or neuron electrical activity on an acquisition computer, the natural analog signal needs to be converted into a digital signal. This is done by analog-to-digital converts which are incorporated into all electrophysiology systems. The major difference between analog and digital signal transmission in wired systems is the stage at which the digital conversion takes place..
How Digital Signals are Contributing to Neuroscience Research
The development of new digital “micro” technology has popularized digital systems in neuroscience by changing the way that the neuronal signals are processed. Analog systems traditionally work by digitizing the brain signal when it reaches the system hardware. This means that the signal passes through a tether before being digitized and is susceptible to external environmental noise. With digital systems, the signal is digitized directly at the head of the animal. This results in less weight on the animal’s head, which for freely moving experiments means that results are less impacted by stress caused from the weight of the set-up on the animals. It also means that higher channel recordings are now accessible in smaller species such as mice and rats. Before digital systems, due to the weight of the accessories, the maximum channel count for mice was 32 channels and 64 channels for rats (at a push). Now, if researchers use digital systems and extra-light high-density silicon probes, channel counts of up to 128 are easily possible in rodents.
The cost of digital systems compared to analog systems is also something to consider. Since open-source electrophysiology systems have become commercially available, the cost of setting up a complete “high-density” electrophysiology system has decreased exponentially. For example, a 128-channel analog system would cost over €100’000. In the past, unless you were part of a very well funded institute, being able to acquire a system without a massive grant would be very unlikely. In today’s market, a 128-channel digital system works out at less than €25’000 (including the cost of a 128 channel probe from diagnostic biochips)! It is no longer the case that only heavily-funded labs can afford electrophysiology systems. Digital systems have made electrophysiology more accessible to everyone.
Another major hurdle with high-density analog recording is the sharing and reproducibility of data among lab groups. As different labs are using different company products that all save files in their own format, sharing of data among different researchers has proven very difficult.
Companies such as Diagnostic Biochips, who develop ultra light-weight silicon probes for high-density recordings, are tackling this hurdle by offering an open-source platform for big-data sharing. Users can record up to 128 channels in mice or rats, allow the software to analyze, and then share the data via the cloud. It is these kinds of digital advancements in neuroscience that are accelerating our understanding of the brain.
Green Leaf Scientific supplies a range of specialty neuroscience research products for both in vivo and in vitro studies. We have a range of suppliers such as Diagnostic Biochips Inc., Pinnacle Technology Inc. and more! Our supplier’s products can be found in neuroscience research labs worldwide, helping to better humanity’s understanding of how the nervous system works in many different aspects. Find out more about the major differences between analog and digital systems in our ‘From Analog to Digital’ infographic.