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Reflexive startle myography

Reflexive startle myography is concerned with quantifying the strength of a startle reaction by measuring the activity of the muscle responsible for closing the eyelid (orbicularis oculi muscle) and calculating the strength of stimulus evoked responses. For the analysis in EMEGS, it is irrelevant how startle reactions were elicited, it is however crucial to know when the eliciting stimuli were delivered.


Preparation

Before running a STARTLE analysis, the onset of the startle probes must be made available in a timing-file or in the database with the corresponding tag specified on the STARTLE configuration page of the Configure-Study-Dialog (shown below). The tag used in the example below reads startle, but can be chosen arbitrarily when running the MARKER analysis, provided that the selected tag name matches the tag name in the STARTLE configuration.



A timing-file compatible with the settings shown above could look like this: it has a subsection tagged startle and this subsection contains only the onsets of startle probes. Other stimuli (in this case pictures used as background stimuli in the subsection tagged eda) should be excluded from the startle subsection.

Condition    Start    End    Duration    SegmentNr    ConditionNr

eda:

11    129.4570312    137.4824219    8.0253907    1    1
21    146.3925781    153.4179688    7.0253907    2    1
31    162.8886719    170.9140625    8.0253906    3    1
31    190.9746094    198.9902344    8.015625     4    2
                        ...

startle:

51    153.4199219    153.5175781    0.09765625    1    1
51    215.5566406    215.6542969    0.09765625    2    2
61    250.8378906    250.9375       0.099609375   3    1
41    285.359375     285.4589844    0.099609375   4    1
51    318.1699219    318.2675781    0.09765625    5    3
41    350.9902344    351.0878906    0.09765625    6    2
61    402.0664062    402.1640625    0.09765625    7    2
61    459.859375     459.9570312    0.09765625    8    3
                        ...


Startle analysis

Once the timing information has been prepared, you can start the STARTLE analysis by clicking on the "Open datafile"-button and select the raw datafile to analyze. EMEGS will display the import signals dialog as usual ...

                                                      
In this case, data was collected at a sampling rate of 512 Hz, which is not optimal (bacause too low) for the STARTLE analysis (this was due to a limitation of the portable measuring device, which just can't go any faster).

EMEGS will then load the data and preprocess it according to the STARTLE configuration. You can adjust the lowpass and highpass cut-off frequencies and the stop-band center frequency according to your needs, but you must do so before starting the analysis. The progress of the preprocessing is shown on the log docking widget.

After preprocessing, startle trials are displayed for manual scoring. The topmost signal is a visualization of the probe onset marker (at the rising flank), the second ist the filtered EMG signal before rectification, the third is the EMG signal after rectification with just a little bit of smoothing, the fourth signal is the rectified and smoothed signal used for amplitude scoring. Signals 2 and 3 are used for response onset detection with the vertical blue line at the recognized onset. Signal 4 has a red circle at the recognized response maximum. The vertical green lines mark the baseline window, which comprises the 50ms before probe onset by default. The horizontal green lines illustrate the mean baseline level (lower line) and the response threshold (upper line), which is at the mean baseline level plus three standard deviations.

For each trial, the baseline and response windows can be adjusted, and the response onset and maximum can be reset manually in the data window by drag-and-drop of the corresponding graphical markers. Responses with amplitudes below the response threshold should in most cases be scored as ZERO responses, whereas responses with a blink in the baseline window should be scored as INVALID. If the signal during the baseline window is not a blink but is generally noisy or artefactually distorted, the baseline window should be adjusted

On the scoring docking widget, the current trial can be scored as "good" using the ACCEPT-button, as a "null" response using the ZERO-button, or as "invalid" using the INVALID-button. Each of these decision will move the scoring window automatically to the next trial. Below these buttons, the status of the current trial is displayed, including the total number of trials and the current trial condition. You can navigate backward or forward without making any scoring decision using the navigation section above, or the "jump to"-dropdown-box.



Once you've finished editing, click on the "Resume analysis"-button to save the results in the database.

You can save the results at an earlier stage using the "Save edited data"-button, and restart the analysis later on to resume the editing (not supported yet).



Value export

To export the results from the database:

  1. load the list of RAW data files to export corresponding data of in the batch docking widget




  2. open the value-export dialog from the Tools-menu (\Tools\Value export), and activate Database data, startle  and files in batch on the data-in page as shown below (in this
    example, only the STARTLE_AMPLITUDE and STARTLE_CONDITION variables were selected - you can select the variables by clicking on the "..."-button next to the
    startle checkbox).



  3. activate mean and timing files on the intervals page as shown below:



  4. select an output file name on the data-out page as shown below:



  5.  click OK. The start of the output file should look something like this:



Subject    Session    SegmentNr    Condition    ConditionRepeat    SourceChannel    Parameter    SignalName    Data
111    1     1    51    1    EMG    avg    STARTLE_AMPLITUDE    6.86645
111    1     1    51    2    EMG    avg    STARTLE_CONDITION    51
111    1     2    51    3    EMG    avg    STARTLE_AMPLITUDE    1.83838
111    1     2    51    4    EMG    avg    STARTLE_CONDITION    51
111    1     3    61    1    EMG    avg    STARTLE_AMPLITUDE    2.85668
111    1     3    61    2    EMG    avg    STARTLE_CONDITION    61
111    1     4    41    1    EMG    avg    STARTLE_AMPLITUDE    6.88834
111    1     4    41    2    EMG    avg    STARTLE_CONDITION    41
111    1     5    51    5    EMG    avg    STARTLE_AMPLITUDE    0.816156
111    1     5    51    6    EMG    avg    STARTLE_CONDITION    51
111    1     6    41    3    EMG    avg    STARTLE_AMPLITUDE    0.34446
111    1     6    41    4    EMG    avg    STARTLE_CONDITION    41
111    1     7    61    3    EMG    avg    STARTLE_AMPLITUDE    5.34824
111    1     7    61    4    EMG    avg    STARTLE_CONDITION    61
111    1     8    61    5    EMG    avg    STARTLE_AMPLITUDE    0.855559
111    1     8    61    6    EMG    avg    STARTLE_CONDITION    61
111    1     9    41    5    EMG    avg    STARTLE_AMPLITUDE    13.5139
111    1     9    41    6    EMG    avg    STARTLE_CONDITION    41
111    1    10    42    1    EMG    avg    STARTLE_AMPLITUDE    0.184871
111    1    10    42    2    EMG    avg    STARTLE_CONDITION    42
111    1    11    52    1    EMG    avg    STARTLE_AMPLITUDE    5.12117
111    1    11    52    2    EMG    avg    STARTLE_CONDITION    52
111    1    12    52    3    EMG    avg    STARTLE_AMPLITUDE    0.702276
111    1    12    52    4    EMG    avg    STARTLE_CONDITION    52
111    1    13    42    3    EMG    avg    STARTLE_AMPLITUDE    0.602816
111    1    13    42    4    EMG    avg    STARTLE_CONDITION    42
111    1    14    62    1    EMG    avg    STARTLE_AMPLITUDE    0.966428
111    1    14    62    2    EMG    avg    STARTLE_CONDITION    62
111    1    15    62    3    EMG    avg    STARTLE_AMPLITUDE    -0.135723
111    1    15    62    4    EMG    avg    STARTLE_CONDITION    62
111    1    16    43    1    EMG    avg    STARTLE_AMPLITUDE    0.194199
111    1    16    43    2    EMG    avg    STARTLE_CONDITION    43
111    1    17    53    1    EMG    avg    STARTLE_AMPLITUDE    0.591396

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