Single-Unit Recording Explained! | Neuroscience Methods 101

In this video we explain how single-unit recording (aka single-cell recording) works.
With single-unit recording we can look at the activity of a single neuron in the brain. As such, it is distinctly different from other techniques such as EEG, MEG, and fMRI. However, for single-unit recording electrodes need to be inserted into the brain. Given the invasive nature, this research is mainly done in animals. But occassionally single-cell recording can be done in humans, if neurological patients receive such recording electrodes to monitor their disorder.
Single-unit recording is an example of an extracellular recording technique. That means an electrode is placed next to a neuron (and not inserted into a neuron as is the case with intracellular recordings). The signal of an extracellular single-unit electrode show are flipped compared to the intracellular action potential.
Since single-units often pick up signals from multiple cells, the neuronal firing needs to be organized. This step is called spike sorting. Since the shape of each neuron looks a little different from its neighbour, we can distinguish spikes from different cells by looking at the amplitude and width of the signal. Finally, the data can be represented in so-called raster plots.
References/resources:
Kamiński, J., Sullivan, S., Chung, J. M., Ross, I. B., Mamelak, A. N., & Rutishauser, U. (2017). Persistently active neurons in human medial frontal and medial temporal lobe support working memory. Nature neuroscience, 20(4), 590-601. doi.org/10.1038/nn.4509
Tseng, H. A., & Han, X. (2021). Distinct Spiking Patterns of Excitatory and Inhibitory Neurons and LFP Oscillations in Prefrontal Cortex During Sensory Discrimination. Frontiers in physiology, 12, 618307. doi.org/10.3389/fphys.2021.61...
Cardin, J. A., Palmer, L. A., & Contreras, D. (2007). Stimulus feature selectivity in excitatory and inhibitory neurons in primary visual cortex. The Journal of neuroscience : the official journal of the Society for Neuroscience, 27(39), 10333-10344. doi.org/10.1523/JNEUROSCI.169...
Graziane, N., Dong, Y. (2016). Extracellular and Intracellular Recordings. In: Electrophysiological Analysis of Synaptic Transmission. Neuromethods, vol 112. Humana Press, New York, NY. doi.org/10.1007/978-1-4939-32...
Hong, G., Lieber, C.M. Novel electrode technologies for neural recordings. Nat Rev Neurosci 20, 330-345 (2019). doi.org/10.1038/s41583-019-01...
Johnson, L., Alekseichuk, I., Krieg, J., Doyle, A., Yu, Y., Vitek, J., Johnson, M., & Opitz, A. (2020). Dose-dependent effects of transcranial alternating current stimulation on spike timing in awake nonhuman primates. Science advances, 6(36), eaaz2747. doi.org/10.1126/sciadv.aaz2747
Narrated by: Miles Wischnewski
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[@beccaapak0228]

Very fun and easy to understan! Thank you so much for making this video!

[@real.psyched]

Thank you! Glad that it helped!

[@Dopamemenergic]

Amazing work!! Your clarification of single-cell vs single-unit (thus intracellular and extracellular) recordings was much needed and shows your knack for making learning digestible and easy!!
Please keep it up!

[@real.psyched]

Thank you! :)

[@ehsansaesh]

amazing. thank you from Iran

[@real.psyched]

Thank you! :)

[@user-qu2ed1bg2e]

Thanks

[@eplv3432]

Amazing presentation thank you! BTW when spike sorting is the amplitude of the peaks inversely related to the distance between the firing cell and the electrode? (As in the bigger peak is closer to the electrode than the ones with smaller peaks)

[@real.psyched]

Thank you for watching! Generally, yes, larger distance correlates to smaller signals. Having said that, other factors play a role too, like size of the neuron, where the electrode is placed (soma, axon, etc), and the type of neuron (inhibitory, excitatory)