spike sorting

Syllable breakdown

Dictionary meaning

the signal processing step in extracellular electrophysiology that assigns detected voltage deflections — spikes representing action potentials — to their individual source neurons by analysing the characteristic waveform shape and other features of each spike; because a single extracellular electrode records the summed activity of multiple nearby neurons, spike sorting is necessary to isolate the contribution of individual cells — single units — from the mixed multi-unit signal; classic spike sorting pipelines involve bandpass filtering to isolate spike-frequency signals, threshold crossing to detect candidate spikes, feature extraction to characterise spike waveforms, and clustering to assign spikes to putative single units; modern automated spike sorting algorithms — Kilosort, MountainSort, SpyKING CIRCUS — use template matching and expectation-maximisation to sort hundreds of units simultaneously from dense electrode arrays with hundreds of channels; spike sorting quality is assessed by cluster isolation metrics, inter-spike interval violations that indicate contamination, and cross-correlograms that reveal putative monosynaptic connections between sorted units

Examples

• Spike sorting of the Neuropixels probe recordings identified 347 putative single units across hippocampus.
• Automated spike sorting with Kilosort reduced the analysis time from weeks to hours.