202308041444
Taken from Buzsaki2004
Spike sorting is a method by which we can isolate single neurons based on extracellular features in multi-unit recordings.
Spike sorting falls into two broad classes:
Separate based on amplitude & wave form variation
Difficult to justify :)
Triangulation
A spike sorting technique by which amplitude and wave shape variation are used to “triangulate” the location of neurons using multiple electrodes (typically a tetrode) and separate individual neuron spikes
- Extent of somatodendritic backpropagation varies as a function of excitatory and inhibitory inputs
- Extracellular spike is a summation of integrated signals from both soma & large proximal dendrites — extracellularly recorded spike parameters depend on extent of spike backpropagation and on other stateand behavior-dependent changes of the membrane potential
- Affects estimation of neuron’s ‘point source’
- Spike amplitude variation is most substantial during complex spike burst production, w/ as much as 80% amplitude reduction bc of Na+ channel inactivation
- Extracellular spike is a summation of integrated signals from both soma & large proximal dendrites — extracellularly recorded spike parameters depend on extent of spike backpropagation and on other stateand behavior-dependent changes of the membrane potential
- Improved spike sorting methods analyzes amplitude AND wave shape variation of spikes
- Limitation: Point-source assumption does not always hold when neurons are equally recorded from
- Can be circumvented by recording at multiple sites parallel with axodendritic axis of neurons
- Can also be exploited for study of behavior-dependent intracellular features & and for resolving temporally superimposed spikes of different neurons
- Cumulative human errors resulting from multiple site-recorded data
Network Identification
- In the hippocampus, several features including spike duration, firing pattern and rate, spike waveform, and relationship to field patterns can be used to separate pyramidal cells from interneurons & some interneuron classes from each other.
Cell type separation
- In the hippocampus, several features including spike duration, firing pattern and rate, spike waveform, and the relationship to field patterns can be used to separate pyramidal cells from interneurons and some interneuron classes from each other.