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  Subject:   decomposition output
 
From:   Faezeh Date:   22 Jul 2009 11:52 am  
Reply via e-mail to Faezeh.  
  Hello,

I have a question about importing the decomposition results from emglab to matlab. I am wondering
if one can send the list of MUPs assigned to a MU from emglab to matlab workspace. The parameter
muap (right clicking on the number of MU in template panel)
only gives a single shape (similar to the template - with a lower number of samples).

Also, I am sort of confused with the way ifrs are calculated. The number of ifr values for a single
MU is way higher than the number of firing times for that MU. For example, I have 50 MUPs for MU1,
but I have a few hundreds of ifr samples for that MU! There is a box in Firing Panel, where one can
set a freuency (0.5, 1, 2, 4, 8, ... Hz) with which the look of ifrs plot changes.
(the smaller this frequency the smoother the curves will be).


Thank you very much,
Faezeh

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  Subject:   Re: decomposition output
 
From:   Kevin McGill Date:   22 Jul 2009 8:23 pm  
Reply via e-mail to Kevin McGill.  
  Hi Faezeh,

You can get the list of times at which a MU discharged by right clicking on the MU number in the Template Panel, selecting Export, and then selecting "Firing pattern." This will send the list of times to the Matlab workspace.

If you want the waveforms of all the discharges (like you see when you select Cascade in the View menu), you can download the file getMUAPdischarges.m from http://www.emglab.net/utilities. If you give this command to Matlab:

>> x = getMUAPdischarges (1);

the function will return all the discharges of MU 1 in an array. There are other optional arguments that are described in the function comments. We will include the capability to export the discharges directly from EMGlab in a future version.

The IFR (instantaneous firing rate) is a continuous function that shows how the MU firing rate fluctuates in time. The mean value of the IFR is the mean firing rate. But MUs do not discharge at a perfectly constant rate. The actual firing rate fluctuates from discharge to discharge because of synaptic noise, and over longer intervals because of modulation of the descending and peripheral drive. The IFR attempts to show these fluctuations. Similarity in the IFR fluctuations of multiple MUs is referred to as "common drive."

If you think of the MU firing pattern as a frequency-modulated signal, with the mean firing rate being the carrier frequency and the fluctuations from the mean firing rate being the modulation, then the IFR is the de-modulated signal. The pop-up menu in the Firing Panel specifies a low-pass filter for the IFR plots. Usually this should be set to about 2 Hz to smooth the random fluctuations while keeping the common drive.

Exporting the IFR to Matlab gives an array containing the samples of the continuous IFR at a sampling rate of 100 pps, with nans at time points at which the MU is not active.

Best of luck with your research,
Kevin McGill



Faezeh wrote:
>Hello,
>
>I have a question about importing the decomposition results from emglab to matlab. I am wondering
>if one can send the list of MUPs assigned to a MU from emglab to matlab workspace. The parameter
>muap (right clicking on the number of MU in template panel)
>only gives a single shape (similar to the template - with a lower number of samples).
>
>Also, I am sort of confused with the way ifrs are calculated. The number of ifr values for a single
>MU is way higher than the number of firing times for that MU. For example, I have 50 MUPs for MU1,
>but I have a few hundreds of ifr samples for that MU! There is a box in Firing Panel, where one can
>set a freuency (0.5, 1, 2, 4, 8, ... Hz) with which the look of ifrs plot changes.
> (the smaller this frequency the smoother the curves will be).
>
>
>Thank you very much,
>Faezeh
>
>
  >> Reply to this message  

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