What is ephys?Technical support engineer at Blackrock Microsystems demonstrates ephys stimulation system

Generally speaking, electrophysiology is the study of the movement of electrical charges in biological tissues. Many different biological tissues control and interact via such moving charges. Therefore, there are many different areas of electrophysiology. But typically the most electrically active cell types, muscles and neurons, are considered when discussing electrophysiology. Blackrock products are primarily focused on neurons, but have the capability to record muscle-cell activity as well.

What measurements are made in ephys research?

Types of signals and analysis

The question is, what exactly are we recording when we analyze a cell’s electrical activity? On the whole, electrophysiologists are concerned with cell membrane potential. Most cell types have ion pumps that allow them to regulate their resting potential. But neurons are special in that they undergo rapid changes in potential in the form of action potentials as part of their cell function. These action potentials are the cell activity that permits neurons to communicate with each other and other cells, which explains why many neuroscientists wish to record these activities.

Neuron signal size is a major challenge

The electrical potential across the cell membrane is approximately
-70 mV at rest and up to +40 mV when depolarized during an action potential. But these numbers are only observable with intracellular recordings. Extracellular recordings, which allow a much greater number of neurons to be examined at once with less invasive techniques, only receive signals on the order of 100-to-800 µV. These tiny signals can be difficult to pick up amidst the buzz of activity in the brain or compared to the numerous electric fields present everywhere in our lives. Recording these signals requires highly specialized equipment and is the reason that the discussion of electrophysiology is so closely tied to equipment used.

Equipment for capturing and analyzing ephys signals

The most instrumental piece of equipment for recording cell activity is the electrode itself. The size, shape, and material of the electrode directly impact the recording capabilities. In general, to record neurons at the resolution of individual cells requires a very high impedance electrode with a very small tip surface area. This minimizes the listening radius to record the activity of a single cell. As impedance lowers and surface area rises, the listening radius expands so the electrode takes in the more general potential/activity of a group of cells. This is commonly known as local field potential (LFP) recording.

Signal amplification and conditioning

Because various electric fields and other potentials in the body can easily overwhelm these small signals, the signal from the electrodes is typically directed into differential amplifiers, which remove electrical noise common to both the reference electrode and the recording electrodes. The amplifier then passes the signals on to processing where they can be filtered for better viewing of the desired information.

There are many ways to group and organize these steps of the process, and many steps can be improved upon with developments in technology, such as the use of digitization to make signals immune to noise and transmissible over longer distances with a lower number of wires or the use of buffer stages to further reduce the susceptibility of the signal to noise.

A comprehensive solution is critical

Blackrock offers all the products comprising such a system—from electrodes and processing instrumentation to signal analysis and behavioral monitoring systems. Moreover, each setup is uniquely configured to meet the needs of the individual neuroscience researcher and project.

Project funding needs and issues

The Blackrock Experts team has years of electrophysiology experience both in academic and commercial settings. We are with you every step of the way from determining equipment requirements for a given project, to system installation and training, to continuing support for the lifetime of your system. An electrophysiology recording system is a significant investment and becomes the cornerstone of lab activity for years to come. For budgetary reasons, equipment needs typically have to be resolved at the grant submission phase, and Blackrock experts can help you configure the system that best balances the goals of the lab with your available budget.

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