spike sorting for extracellular recordings kenneth d. harris rutgers university
Post on 02-Jan-2016
238 Views
Preview:
TRANSCRIPT
Spike Sorting for Extracellular Recordings
Kenneth D. HarrisRutgers University
Aims
We would like to …
Monitor the activity of large numbers of neurons simultaneously
Know which neuron fired when Know which neuron is of which type Estimate our errors
Extracellular Recording Hardware
You can buy two types of hardware, allowing
Wide-band continuous recordings
Filtered, spike-triggered recordings
The Tetrode Four microwires twisted into a
bundle Different neurons will have
different amplitudes on the four wires
Raw Data
Spikes
High Pass Filtering Local field potential is primarily at
low frequencies.
Spikes are at higher frequencies.
So use a high pass filter. 800hz cutoff is good.
Filtered Data
Cell 1
Cell 2
Spike Detection Locate spikes at times of
maximum extracellular negativity
Exact alignment is important: is it on peak of largest channel or summed channels?
Data Reduction We now have a waveform for each
spike, for each channel.
Still too much information!
Before assigning individual spikes to cells, we must reduce further.
Principal Component Analysis Create “feature vector” for each spike.
Typically takes first 3 PCs for each channel.
Do you use canonical principal components, or new ones for each file?
“Feature Space”
Cluster Cutting Which spikes belong to which
neuron?
Assume a single cluster of spikes in feature space corresponds to a single cell
Automatic or manual clustering?
Cluster Cutting Methods Purely manual – time consuming,
leads to high error rates.
Purely automatic – untrustworthy.
Hybrid – less time consuming, lowest error rates.
Semi-automatic Clustering
Cluster Quality Measures Would like to automatically detect
which cells are well isolated.
Will define two measures.
Isolation Distance
L_ratio
21ratio clusternoise
L cdf N
False Positives and Negatives
Room for Improvement? Improved alignment methods, leading
to nicer clusters.
Faster automatic sorting.
Better human-machine interaction.
Fully automatic sorting.
top related