Silicon Probes v Electrodes for Large Scale Neurophysiology Recordings
Electrodes have been used for almost a century in order to record electrical activity from the nervous system. The ability to conduct currents produced by biological processes has allowed researchers to understand neuronal activity from the brain and spinal cord, and sets the basis for the whole field of electrophysiology. By amplifying the signal recorded from the electrode and digitizing it, neuronal activity can be visualized, analyzed and recorded. In labs all over the world, animal models of neuroscience are implanted with electrodes in different forms to better understand neural circuitries, brain anatomy, brain function and neurodegenerative diseases.
Electrodes are relatively simple by design, and many electrophysiology labs build electrodes themselves using Copper, Tungsten or silver. You can easily google “how to make an electrode” and find a video on YouTube that shows you how to do it in less than 10 minutes. This has made them a very desirable and cheap option for many labs when combined with data acquisition systems.
For labs looking to do high-channel count recordings, it usually involves 4 electrodes merged or twisted together to create a tetrode. These tetrodes can then be used in multiples ( for example, 4 x 4 tetrodes for 16 channels) in order to record more activity from the brain, giving more data for analysis. The problem with using too many electrodes within one animal model is the potential damage to the brain tissue in the process, and the weight of the associated accessories that transmit the electrodes signal. This limits the number of channels that can be recorded from mice (maximum usually 32 channels) and rats (maximum usually 64) with electrodes/tetrodes.
Silicon probes are commercially developed electrode shanks that integrate many electrodes onto the same implantable device. While more expensive by design, they have a much higher channel count than single electrodes and allow for higher-channel counts never before possible with electrodes or tetrodes alone. They are light-weight by nature and require less accessories to transmit the signal to the acquisition system, meaning less stress is put on the animal. Their linear structure allows simultaneous recording from different laminar structures (layers) of the brain which is not possible with tetrodes. They can also access deeper brain regions more easily than electrode recordings, especially using deep-brain arrays.
While many labs have years of experience successfully recording using electrodes in rodent models, silicon probes are a more reliable option for those just starting out or wanting to increase their channel count. There is a lot less work required and a lot of time saved by using commercially available probes. While it is not recommended to reuse probes in different subjects for long-term studies, probes may be re-used in acute experiments following correct protocol.
Although silicon probes are more expensive than electrodes, they are developed to be compatible with digital acquisition systems. Many data acquisition systems manufacturers have moved from analog to digital technology, meaning systems are a lot cheaper than they were a few years ago. As a result, complete systems including high-density silicon probes are now more easily accessible to labs. Diagnostic Biochips (partnered with Open EPhys) offer researchers complete digital acquisition systems with their desired silicon probe. See the full list of probe configurations here.
For studies looking to record local field potentials (LFPs) at the surface of brain regions, such as cortical recordings, electrodes are an ideal solution. Low density acquisition systems that record 1 or 2 EEG channels often integrate additional modalities that allow for recording of other activity, such as EMG. Pinnacle Technology offers a range of in vivo electrophysiology systems ideal for sleep and seizure research, with both tethered and wireless options available. Biosensors to monitor neurotransmitter activity can also be incorporated into the systems to simultaneously measure both electrophysiology and biochemical activity!
Check out our newest infographic which outlines the advantages and disadvantages of Silicon Probes and Electrodes for Large Scale Neurophysiology Recordings.
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.
Is your lab looking for some new equipment? Check out our range of specialized neuroscience research products, and don’t forget the number of factors to consider when deciding how to record from the specific brain region of interest.