Muscle Innervation - Cross Correlation

Here we present a study of multi-terminal innervation in the superficial flexor muscle of an arbitrary crayfish tail segment. Channel 1 of the data set includes extracellular recording from the multi-unit third nerve offshoot of the ventral cord ganglion and channel 2 contains a simultaneous intracellular recording of the superficial flexor muscle which the nerve innervates.

Multiple amplitude spikes are extracted and correlated with the muscle potentials to detect relative connection strengths in the muscle, delay due to propagation down the length of the neuron and through the neuromuscular junction, and rate of transmitter release (slope of the post synaptic potential rise, PSP).

Students in BioNB491 at Cornell University in spring of 2007 used the initial slope of the PSP as a connection strength independent measure of the rate of transmitter release at a synapse. For example, when caffeine was added to the preparation, the slope of the PSP rise changed dramatically correlating with what we know about caffeine releasing intracelluar stores of calcium and therefore upping the number of vesicles released per action potential event.

Raw Data Files

• rec4.mat - 10 second recording of passive activity on channel 1 and muscle membrane potential on channel 2 -- .wav
• rec4-large.txt - Subset of analysis values for the larger amplitude spike
• rec4-small.txt - Subset of analysis values for the smaller amplitude spike

 

Two extracted subsets of data from the extracellular recording of the nerve innervating the muscle

1. Load rec4.mat into the analysis window, select channel 1
2. In the analysis menu, select a low pass filter at 1000Hz and hit calculate (remove high frequency noise)
3. Turn on threshold 1 and set it to -0.024 (as the threshold is below the median of the signal, it will detect threshold crosses going in the negative direction).
4. Press the calculate button
5. Hit the extract square button and draw a square in the analysis window to include the sparse larger amplitude spikes (figure bottom left). From the options menu of the extracted set figure choose "save analysis values" and save it as "rec4-large.txt"
6. Repeat the process for the smaller amplitude spikes (figure bottom right) and save as "rec4-small.txt"

 

The results of correlation of spike subsets with the post synaptic membrane potential in the muscle innervated by the neurons. High degree of correlation is detected with different PSP initiation delays and initial slopes (note that vertical axes are not at the same scale. Note that the smaller spike clearly activates the PSP at 5ms after the spike is recorded and the larger spike initiates PSP at approximately 3ms after the spike is recorded.

1. Load rec4.mat into the analysis window, select channel 2 (the intracellular recording)
2. Select "Correlate File with Extracted" from the analysis menu
3. Select "rec4-small.txt" as saved above
4. Use the default window width of 0.05s, locate window after threshold cross and include all traces in the background
5. Repeat for "rec4-large.txt"

This gives a demonstration of cross channel correlation and may be utilized in any event that you think there may be a signal with temporal correlation between multiple channels (or within the same channel) of recordings.