[Eeglablist] simple question about epoch and event

[Makoto Miyakoshi]

Dear Min,

Sorry for delay.
Well, the number of epochs and events could be different.
If you have event A every 1 seconds for 100 times. If you epoch +/- 500 ms,
you'll have 100 epochs and 100 events i.e. one event per epoch. If you
epoch +/- 1000 ms, you'll have 100 epochs and 300 events because your 3
second epoch now contains n-1th, nth, and n+1th event.

Makoto


2013/10/28 Stephen Politzer-Ahles <politzerahless at gmail.com>

> Hi Min,
>
> This depends on some options that you select while epoching. For example,
> it's possible that EEGLAB may not have made two epochs out of two identical
> events that are close together (there is an option for that) or events
> occurring very early or late in the recording (there are also options for
> that). It would be helpful if you could provide more information about the
> commands that you called for epoching.
>
> best,
> Steve
>
>
>
> Stephen Politzer-Ahles
> New York University, Abu Dhabi
> Neuroscience of Language Lab
> http://www.nyu.edu/projects/politzer-ahles/
>
>
> On Sat, Oct 26, 2013 at 12:53 AM, Min Sheng <Min.Sheng at utsouthwestern.edu>wrote:
>
>>  Dear all,
>>
>> I am new to EEG process, I am a little confused about the epoch and the
>> event. When I use eeglab to extract epochs from raw data, I thought the
>> number of   event and the epoch should be the same, but it didn't. For
>> example,  if I extracted 'S32' epochs and generated new data set, it showed
>> that the number of epochs is 755 while the number of events is 758.
>> However, the VMRK file shows the number of 'S32' should be 756. It happened
>> when there were some  other markers mixed (like 'buffer overflow') during
>> the recording.
>>
>>
>>
>> Best regards,
>>
>> Min sheng
>>
>>
>>
>> ------------------------------
>>
>> UT Southwestern Medical Center
>> The future of medicine, today.
>>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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