[Eeglablist] When to perform re-reference?

Makoto Miyakoshi mmiyakoshi at ucsd.edu
Mon Jun 23 09:56:40 PDT 2014


Dear Brian,

The average referencing is not affected by epoch rejection (assuming that
bad EEG is restricted to the epochs that are rejected) or component
rejection. In your case, average referencing can be done either before or
after two ICAs.

I'm still waiting to hear from Jason though whether it's better to do
average referencing before ICA and if so, why.

Makoto


On Thu, Jun 19, 2014 at 8:37 AM, Brian Scally <scallybrian at gmail.com> wrote:

> Hi there,
>
> I have been following the discussion. So it is recommended to re-reference
> to average after removing channels/epochs and right before running
> ICA. Suppose I plan on running ICA twice: the first time to identify epochs
> that are affected by improbable components, after which the epochs will be
> removed. The second time would be to remove actual components. Do I need to
> re-reference before the first, or will before the second suffice?
>
> Cheers,
> Brian
>
>
> On 19 June 2014 00:56, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:
>
>> yes.
>>
>>
>> On Wed, Jun 18, 2014 at 3:45 PM, Jerry Zhu <jerryzhu at siu.edu> wrote:
>>
>>> Hi Makoto,
>>> Thank you again for your reply.
>>>
>>> Did you mean "averaging AFTER removing bad epoches" in your sentence
>>> "you should apply average referencing AFTER removing bad channels."?
>>>
>>> So here are my processing:
>>> 1) re-reference  (from Cz to average in my case)
>>> 2) remove bad epoches
>>> 3) interpolate bad channels
>>> 4) ICA
>>>
>>> Sounds like you would recommend the order: 2143?
>>>
>>> Looking forward to your and others inputs!
>>> Thanks all!
>>> Jerry
>>>
>>> --
>>> Jian Zhu, M.A.
>>> Brain and Cognitive Sciences
>>> Department of Psychology
>>> Southern Illinois University Carbondale
>>> Web: http://zhupsy.com
>>>
>>> We have two halves in the brain: left and right. Nothing is right in the
>>> left. Nothing is left in the right.
>>>
>>>
>>> On Wed, Jun 18, 2014 at 1:38 PM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu>
>>> wrote:
>>>
>>>> Dear Jason,
>>>>
>>>> I remember you said that average reference should be applied before
>>>> ICA, but I did not understand exactly why. Could you comment on this?
>>>>
>>>> Jerry, you should apply average referencing AFTER removing bad channels.
>>>>
>>>> I don't think it makes big differences between average referencing
>>>> before or after interpolation. However we don't necessarily recommend
>>>> interpolation before ICA.
>>>>
>>>> Makoto
>>>>
>>>>
>>>> On Tue, Jun 17, 2014 at 12:20 PM, Jerry Zhu <jerryzhu at siu.edu> wrote:
>>>>
>>>>> Hi all,
>>>>> At which stage do you re-reference your data? It was suggested do
>>>>> re-ref before ICA (
>>>>> http://sccn.ucsd.edu/pipermail/eeglablist/2011/003795.html). How
>>>>> about re-ref before/after bad epochs rejection and bad channel
>>>>> interpolation? The note here  (
>>>>> ftp://ftp.egi.com/pub/documentation/technotes/SplineInterpolation.pdf)
>>>>> suggests after interpolation. ("Since the interpolated potentials can be
>>>>> used to better approximate the average reference (Junghofer et al., 1999),
>>>>> it may be somewhat advantageous to compute the interpolated potentials
>>>>> directly from the measured data, in which case the voltages below are best
>>>>> thought of as referring to these measured potentials")
>>>>>
>>>>> What is your experience? Thanks for your sharing and suggestions!
>>>>>
>>>>> Jerry
>>>>> --
>>>>> Jian Zhu, M.A.
>>>>> Brain and Cognitive Sciences
>>>>> Department of Psychology
>>>>> Southern Illinois University Carbondale
>>>>> Web: http://zhupsy.com
>>>>>
>>>>> We have two halves in the brain: left and right. Nothing is right in
>>>>> the left. Nothing is left in the right.
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Makoto Miyakoshi
>>>> Swartz Center for Computational Neuroscience
>>>> Institute for Neural Computation, University of California San Diego
>>>>
>>>
>>>
>>
>>
>> --
>> Makoto Miyakoshi
>> Swartz Center for Computational Neuroscience
>> Institute for Neural Computation, University of California San Diego
>>
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>
>
>
> --
> Brian Scally
>



-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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