Matlab Code Presentation

Discharge characteristics of motor units during long contractions Michael Pascoe, M.S.

Background • Motor unit • Functional quantum of the neuromuscular system

• Comprises an alpha

MN, its axon, and all the muscle fibers it innervates

Research Questions

• How long can a human voluntarily activate a motor unit?

• How does the discharge behavior change with time?

Surface EMG Abduction force Fine wire SMU

Spike2 - Sample Data 0.75 V

MU

iEMG

0.75 V

1V

sEMG

5 %MVC

Force

100 s

Flowchart Spike2 Data

mu_anal_longdur.m

Motor Unit Discharge Times

Divide Into 5 Equal Duration Epochs

Interspike Intervals

Filter Out Long Intervals (> 250 ms)

Filter Out Short Intervals (< 10 ms)

Calculate Discharge Characteristics

SpikeStats.txt

Input

Epoch Boundaries epoch(1)

epoch(2)

epoch(3)

epoch(4)

epoch(5) 0.75 V

MU

iEMG

0.75 V

1V

sEMG

5 %MVC

Force

first spike

100 s

last spike

Creating Equal Duration Epochs for i = 1:length(dis) if (dis(i) < epoch1_end) epoch(1).values(j) = dis(i); j=j+1; elseif (dis(i) > epoch1_end & dis(i) < epoch2_end) epoch(2).values(k)=dis(i); k=k+1; elseif (dis(i) > epoch2_end & dis(i) < epoch3_end) epoch(3).values(l)=dis(i); l=l+1; elseif (dis(i) > epoch3_end & dis(i) < epoch4_end) epoch(4).values(m)=dis(i); m=m+1; elseif (dis(i) > epoch4_end & dis(i) <= dis(end)) epoch(5).values(n)=dis(i); n=n+1; end end

Create interspike intervals % Determine interspike interval in seconds isi(i).values = diff(epoch(i).values);

Filter interspike intervals % Remove ISIs greater than 0.25 or less than 0.01 s (<4 or >100pps) isi(i).values = isi(i).values(find(isi(i).values<0.25 & isi(i).values>0.01)); sizeisifilt(i).values = size(isi(i).values);

Discharge Characteristics • Mean discharge rate • Standard deviation of

• Mean interspike interval • Standard deviation of

• Coefficient of variation

• Coefficient of variation

discharge rate

for discharge rate

interspike interval

for interspike interval

• Standard error of the

mean of discharge rate

Stein et al. Nat Rev Neurosci 2005, 6: 389-397

Output

Output • A single text file (one trial) • Subject initials and date preserved • _SpikeStats.txt in place of _Times.txt • Column headers in first row • Output variable values in five rows

Output

Output

Trial Name Mean DR (pps-direct) Mean D BKB_(11_21_2007)_Times 11.24653 10.682879 11.581364 9.844349 9.934456

Validation Epoch(5) MeanDR (pps) Std Dev DR (pps) CV DR (%) Mean ISI (ms) Std Dev ISI (ms) CV ISI (%) Start Time (s) End Time (s) Train Dur (s) No. Impulses No. ISIs ISIs < 10 ms ISIs > 250 ms

MATLAB 7.334067 1.093795 14.913897 136.35 55.07046 40.389043 919.57823 974.89423 55.18775 39 38 0 46

Spike2 7.33 1.09 14.91 136.35 55.07 40.39 919.578 974.894 55.188 39 38 0 46

In the near future... • Analysis of surface EMG • Analysis of index finger abduction force • Distribution statistics for discharge times