2 Neuroscience2.3 Basic techniques in neuroscience
2.3.1.1 Single unit recordings
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Written by Resident Doctor Committee · Published
What a single unit recording measures
Single unit recording isolates the spikes of one neurone, and its information lies mainly in spike timing and firing rate.
Attribute | Intracellular | Extracellular |
|---|---|---|
Tip | Inside the cell | Beside cells |
Signal | Membrane potential, including subthreshold events and spikes | Action potential currents from nearby cells |
Practicality | Invasive and hard to hold during movement | Stable in behaving animals, but units must be separated |
Patch clamp
Patch-clamp recording measures the picoamp current through single ion channels in the cell membrane.
A glass micropipette seals to the membrane with a gigaohm-resistance seal (gigaseal), which holds the voltage and keeps leakage low enough to measure channel current.
Voltage clamp measures current while the voltage is held at a set value.
Cell-attached recording keeps the patch intact, and rupturing the patch gives whole-cell access.
Neher and Sakmann received the 1991 Nobel Prize for the method.
At the gamma-aminobutyric acid type A (GABA-A) receptor, benzodiazepines increase how often the channel opens, while barbiturates prolong each opening.
Spike sorting
Spike sorting groups similar waveforms into putative units, and poorly separated signals are reported as multi-unit activity.
Landmark findings
Finding | Researcher | Site |
|---|---|---|
Orientation selectivity and ocular dominance columns | Hubel and Wiesel | Primary visual cortex |
Place cells | O'Keefe | Hippocampus |
Grid cells | The Mosers | Entorhinal cortex |
Reward prediction error | Schultz | Ventral tegmental area and substantia nigra |
Mirror neurones | Rizzolatti | Macaque premotor cortex |