@@ -34,18 +34,18 @@ directly manipulate signal arrays. If you intend to use the ICA toolbox
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functions underlying EEGLAB, EEGLAB itself is a good starting point and
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introduction. EEGLAB also provides a full EEG structure to describe your
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data (signal, trials, channel location, reaction time, type of the
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- trials, time limits and sampling rate) and allows you use this structure
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+ trials, time limits and sampling rate) and allows you to use this structure
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either from the MATLAB command line or in MATLAB scripts.
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- ### Is MATLAB too slow and does it use too much memory ?
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+ ### Is MATLAB too slow and does it use too much memory?
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** Answer:** Yes, to an extent, but... Because MATLAB sometimes uses large amount of RAM, we also took great care of inserting
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options in EEGLAB and in several processing functions to handle low
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memory conditions. On the other hand the MATLAB environment offers the
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advantage of stability and ease of use. Even the novice user under
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MATLAB can scale a data array by multiplying it by a scalar for instance
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(and in our software the data array is directly accessible to the user).
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- MATLAB also offers the advantage of modularity. All of our function are
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+ MATLAB also offers the advantage of modularity. All of our functions, are
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stand-alone functions and most of them can be used independently of each
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other. Besides, MATLAB has grown much faster.
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@@ -68,7 +68,7 @@ Processing toolbox which has to be purchased separately.
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### Overloaded functions
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- under Unix, I often get the following message
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+ Under Unix, I often get the following message
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''Warning: One or more output arguments not assigned during call to
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'XXX'.
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@@ -87,7 +87,7 @@ variable or rename the function.
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- Buy more memory (RAM) for your computer
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- Try the memory mapping scheme (in EEGLAB options) which will allow
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- to keep the data on disk. Note that expect for Neuroscan files, it
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+ keeping the data on disk. Note that except for Neuroscan files, it
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is still necessary to import the full data file in memory.
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### Multi-core use
@@ -96,8 +96,8 @@ variable or rename the function.
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Does it benefit to have a multi-core machine?
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** Answer:** yes, it benefits in two ways. First, you may start in
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- parallel several MATLAB session . Each of them is assigned one of the
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- processor . Second, if you go to the MATLAB options, you may have the
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+ parallel several MATLAB sessions . Each of them is assigned one of the
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+ processors . Second, if you go to the MATLAB options, you may have the
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option to enable multi-core computation (General \> Multithreading).
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This option is usually set by default. This is a very efficient option
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that will speed up your code usually linearly with the number of core (2
@@ -160,9 +160,9 @@ degrees, but Polhemus (Neuroscan) goes counter-clockwise and EEGLAB goes
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clockwise. We are trying to develop some conversion solution for this,
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but if
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- 1 . you already have some experience w/ a situation like this you may
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+ 1 . you already have some experience w/ a situation like this and you may
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have some easy solution;
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- 2 . you could advice use to get our Polhemus coordinates into EEGLAB
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+ 2 . you could advise us on how to get our Polhemus coordinates into EEGLAB
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some other (easier) way, we would appreciate.
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@@ -192,7 +192,7 @@ specified. For instance I asked for epochs between 0 and 3 seconds at
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125 Hz and end up with an interval of 0 to 2.992 s. There should be
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something wrong!
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** Answer:** Nothing is wrong. In your example, we must draw (125Hz \*
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- 3seconds = 375 points) and not 376 otherwise we would loose time
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+ 3seconds = 375 points) and not 376 otherwise we would lose time
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linearity i.e. 2 epochs of 3 seconds would be 752, whereas if we draw 6
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seconds of the data we would get 751 points !), but if we assign time 0
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to the first point, then we must assign time 2.992 to the last point.
@@ -239,7 +239,7 @@ Functions
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### Missing trials in ERPimage?
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- When using channel ERP image ('Plot' -'Channel ERP
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+ When using the ERP image menu item ('Plot' -'Channel ERP
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image'), the top part of the output is the window with the sorted
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trials. The number of the trials seems to be off and it appears that not
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all trials are displayed. For instance, using a file with 17 trials the
@@ -266,7 +266,7 @@ box of the pop_erpimage() interactive window.
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### Cross-subject analysis of spectral power and coherence?
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- Do you have any good way to to across subject/patient
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+ Do you have any good way to across subject/patient
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analyses with respect to power and coherence, especially making
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statistical comparisons between subjects/patients? Could we somehow use
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the data output of EEGLAB?
@@ -284,13 +284,13 @@ Artifacts
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It is not very difficult to find components related to
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eyeblinks, etc. In my case, there are phases during the experiment,
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- where people speak and/or move there eyes. I find it quite hard to
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+ where people speak and/or move their eyes. I find it quite hard to
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determine which components are related to these artifacts and I already
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wonder if it is possible et all.
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- ** Answer:** To determine wich components are related to these artefacts ,
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+ ** Answer:** To determine wich components are related to these artifacts ,
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one approach is to isolate these trials (selecting them) and then use
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menu item "Plot \> Component ERPs \> With component maps" and select the
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- time window where these event appears . This function will plot which
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+ time window where these event appear . This function will plot which
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components contribute to this type of artifact. However, you are correct
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in thinking that ICA cannot cleanly resolve ALL artifacts into one or a
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few components. For instance, "paroxysmal" artifacts (like the subject
@@ -308,9 +308,9 @@ or more). Also their spectrum does not look like the standard EEG
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### Rejecting artifacts
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I am currently using ica to correct for artifacts. In the
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- past I've visually inspected each single-trial epoch seperately ,
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+ past I've visually inspected each single-trial epoch separately ,
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indentified those trials with artifact activity, and then trained ICA on
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- each trial seperately to identify and remove artifactual components. As,
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+ each trial separately to identify and remove artifactual components. As,
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you can imagine this process is extremely time consuming. Is it
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effective to train ICA on multiple or all concatenated trials at once,
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remove artifactual components, and then go back to visually inspect the
@@ -377,11 +377,11 @@ data rank (see below).
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### Baseline removal and preparing data for ICA
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- What is the rationale behind baseline zero'ing the data
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+ What is the rationale behind baseline zeroing the data
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before running it thru ICA, and is that always recommended?
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- ** Answer:** It is recomended because the EEG might have some electrical
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+ ** Answer:** It is recommended because the EEG might have some electrical
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artifacts (slow trends) that you want to remove. If your data is
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perfectly flat (at very low frequencies), then you shouldn't need to do
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that. You should baseline-zero each epoch, else use the continuous data
@@ -391,7 +391,7 @@ associated with a series of 1-of-a-kind, non-stationary maps). The data
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scrolling utility in EEGLAB makes this convenient, and if you perform
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this on the continuous data, records breakpoint events that guide
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subsequent epoching. Else, you can more severely prune the data to train
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- the ICA model, then pass more of the data through the model (at a cost
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+ the ICA model, then pass more of the data through the model (at the cost
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of somewhat higher SNR (signal to noise ratio) in the activation time
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series).
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@@ -410,7 +410,7 @@ Note we do not recommend using PCA (" 'pca', 4 ") unless you have some
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good reason. Using first PCA components only will truncate the data
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(irrespective of components), and then ICA may not be able to find
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relevant components. The second possibility ("'ncomps', 4") is more
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- acceptable theoritically since it is a true ICA decomposition (that uses
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+ acceptable theoretically since it is a true ICA decomposition (that uses
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a rectangular matrix). In general, we advise finding as many components
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as possible (e.g. if you have enough memory on you computer to run ICA
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over all the channels).
@@ -437,8 +437,8 @@ to use.
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### ICA applied to data epochs or continuous data
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I have noticed that the runica() does not include a field
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- for epoch size, so how does ICA recognize the epochs ? Doesn't this make
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- a difference to the way ICA is handled ?
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+ for epoch size, so how does ICA recognize the epochs? Doesn't this make
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+ a difference to the way ICA is handled?
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** Answer:** Epochs are concatenated before running ICA. In ICA, all time
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points of all epochs are shuffled so that epoch information is
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irrelevant.
@@ -451,7 +451,7 @@ epochs from the data, which are 3000 frames each. There are only about
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Should I apply ICA to the continuous data, then epoch the ICs, or apply
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ICA to the concatenated epochs?
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** Answer:** You can apply ICA to either of them. Usually, we prefer to
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- apply ICA to the concatenated epochs so ICA component are more likelly
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+ apply ICA to the concatenated epochs so ICA component are more likely
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to represent activity related to the task, but continuous data are fine
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too, especially if you have few epochs or few data points, since most of
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the same EEG and artifact processes are likely to be active 'between'
@@ -471,7 +471,7 @@ not expressed in the data at that particular time).
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Time Frequency
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--------------
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- ### Timef() spectral decompositions: properties and discrepencies
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+ ### Timef() spectral decompositions: properties and discrepancies
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Is it not true that the ERP for a condition can be
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completely reconstructed from the timef() results, incuding ITC? One
@@ -491,7 +491,7 @@ results ....
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** Answer:** Yes, this is possible (with some fuzziness regarding
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overlap-adding the overlapping spectral estimates, undoing the effects
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- of tapering (windowing), etc. I havent focused on strictly "invertible"
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+ of tapering (windowing), etc. I haven't focused on strictly "invertible"
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time/frequency transforms - which tend to be restrictive, since I am
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interested in analysis rather than synthesis.
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@@ -539,8 +539,7 @@ the plot's time scale it appears that the epoch is from slightly before
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-2000 ms to slightly over +1500 ms. Do you know why?
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** Answer:** It is normal that the time limits are different from the
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original dataset, since the FFT (or wavelet) is applied over time
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- windows and we consider the center of these windows. As a result, you
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- loose half the window size on each edge of the plot (some hundred
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+ windows and we consider the center of these windows. As a result, you lose half the window size on each edge of the plot (some hundred
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milliseconds depending on the window size and the sampling rate).
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### Spectrum using FFT, Welch or multitaper
@@ -552,14 +551,14 @@ The Thomson method (usually known as multitaper) is good too. It is
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first projecting the data onto an orthogonal base, then performing FFT.
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They should all return similar results (FFT, pwelch, multitaper). I
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- guess the Thomson method is the less sensitive to noise but also the
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- most complex to use. I guess it would also be possible to use the welch
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+ guess the Thomson method is less sensitive to noise but also
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+ more complex to use. I guess it would also be possible to use the welch
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method on top of multitaper. It is all a matter of preference. I would
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advised using the pwelch method which is easy (you just give as an
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option the length of the windows and the overlap). Multitaper would
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require you to select the number of basis vector in your othogonal base
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and this is much less intuitive (and also has consequences on the
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- frequency resolution you can achive ).
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+ frequency resolution you can achieve ).
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### Multitaper, FTT, wavelets for time-frequency decomposition?
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@@ -568,12 +567,12 @@ couple of weeks, especially timef() and crossf(). The multitaper method
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with bootstrap statistics has been giving me very nice stable results.
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Timef() with wavelets gives slightly different results, but also
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interesting. I noticed though that all the analysis has been designed to
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- study coherenece , phase-coherence, ITC, etc, for data organized as
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+ study coherence , phase-coherence, ITC, etc, for data organized as
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epochs. (e.g. inter-trial effects).
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Is there a function for computing time-varying coherence between
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- 'independent' activation functions for continous spontaneous recordings?
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+ 'independent' activation functions for continuous spontaneous recordings?
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(i.e., spontaneous coherence for brief windows of time, 200-300ms). J.P.
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Lachaux (from Varela's Lab) has several papers investigating this issue.
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@@ -673,8 +672,8 @@ too thick. How can I control their thickness?
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** Answer:** To change the figure aspect for publication, you can go in
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the figure menu and use the MATLAB menu item "Tools \> Edit". Then you
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- can select any object in the figure. Second button will display a
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- contextual menu where you will be albe to change line thickness, color,
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+ can select any object in the figure. The second button will display a
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+ contextual menu where you will be able to change line thickness, color,
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font aspects..., or even draw additional lines or add text. We also
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export figures as Postcript files and open them with Adobe Illustrator
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in vector format to fine tune it. See also this web page.
@@ -687,7 +686,7 @@ the scroll channel data eegplot(), and for channel spectra and
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maps...and other plots....
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- ** Answer:** For most EEGLAB figures, sinply use menu item "File \>
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+ ** Answer:** For most EEGLAB figures, simply use menu item "File \>
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Export".
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@@ -722,11 +721,11 @@ how to fix this problem?
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the MATLAB command line by typing: "feature('UseGenericOpenGL',1)" For
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the printing error, we also experience this; it is a MATLAB problem
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which is not consistent between Windows and Linux. We always print or
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- save to files (.jpg or .eps Postcript ), then print the files. For
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+ save to files (.jpg or .eps Postscript ), then print the files. For
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instance, use the software
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[ FreeRawPrint] ( http://download.com.com/3001-2088-10178995.html ) to send
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- the postcript file to the printer under windows. Even with this
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- strategy, some parts of complex figures may disapear , but this is rare
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+ the Postscript file to the printer under windows. Even with this
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+ strategy, some parts of complex figures may disappear , but this is rare
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(then we use screen captures, or use a Windows machine, since printing
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seems to be more reliable under Windows OS). We hope MATLAB will become
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better at this in the future (Is MATLAB listening?).
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