Factors to Consider When Doing Electrophysiology Recordings

At its most basic level, in vivo electrophysiology in neuroscience uses electrodes to measure biosignals that accurately represent brain function. Since its discovery in 1924 by Hans Berger, the first scientist to successfully record biological signals from human brains, it has been developed even further as an extremely powerful research tool. In vivo electrophysiology is now used in research labs all over the world to study both humans and animal models in order to better understand specific functions of different brain regions and neural circuits. The technique has contributed to advancements in our understanding of vital brain functions, animal behaviour, neurocognition, diseases that affect the nervous system, and associated clinical treatments for humans.

Electrophysiology in Animal Research

While a number of discoveries have been made using EEG in humans, invasive recording techniques used in animal research allow for more in-depth studies of specific brain functions. Using invasive electrophysiology techniques means that hypotheses which cannot be answered in human brains, can be studied more intrusively. Examples include; applications such as understanding certain cognitive functions associated with deeper brain regions, animal behaviour under normal and pathological conditions, and transgenic models of neurological disorders and disease.

Rodents are the most commonly used animal model in preclinical electrophysiology studies for a number of reasons, but studies are also done in other mammals, birds, reptiles and even insects. While rats and mice differ in size, both models can facilitate transgenic studies as well as the addition of modules such as advanced neuroimaging or optogenetic integration. They can also reproduce relatively fast, meaning high-throughput studies can be carried out.

Factors to Consider When Doing Animal Electrophysiology Recordings

An important factor to be considered when conducting electrophysiology recordings is how many electrodes/channels will be used in an experimental set-up. While lower channel counts (1-4) are perfect for proof of concept studies or recording LFPs, higher channel counts are required for experiments that are looking at complex brain structures or how two regions interact with each other. Mammalian brains consist of billions of neurons that make up different brain regions with different functions. This means that multiple electrodes need to be used by the researcher to ensure adequate recordings. Channel count is therefore an important factor in ephys experiments, with silicon probes providing an excellent solution for high-channel set-ups. Depending on the research application, the implanted electrodes will be used for either acute (short-term) or chronic (long-duration) recordings.

Freely moving or head restrained studies are carried out depending on the paradigm being studied – some studies involving cognition and sensory modalities such as vision, hearing and touch sometimes require animals to be restrained in order to ensure accurate recording of relevant behaviour. Involuntary or active movement can cause artifacts or noise, which can skew the data depending on the research question, leading to inaccurate results.

While most laboratories focus on a specific research area or application, many do not limit themselves to just one particular neuroscience technique. A single laboratory may have research protocols that involve in vivo electrophysiology recordings from freely moving animals coupled with optogenetic stimulation or fiber photometry; in vitro recordings or neurotransmitter detection from a particular structure of the brain or CNS using microdialysis and HPLC-ECD; and imaging studies such as fluorescence imaging to gather information about brain structures and how they connect with each other.

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Find a glossary of terms for this article in our ‘Electrophysiology’ infographic.