[Eeglablist] What is meant by 'epoch' and 'frames' in EEG Lab

[Stephen Politzer-Ahles]

Hello Rajesh,

Welcome to EEGLAB. "Frames" in EEGLAB are the same as samples (so if you
sampled at 1000 Hz your data will have 1000 frames each second).

As for epochs: you are right that the EEG is collected continuously, but
part of the procedure for analyzing event-related potentials from EEG is to
later "chop" the signal into segments time-locked to an event such as a
stimulus (see Luck, 2005, *An Introduction to the Event-Related Potential
Technique*). EEGLAB treats the continuous data as consisting of one long
epoch, whereas after chopping up the data it consists of multiple small
epochs. So that's why you see EEGLAB reporting that there is one epoch even
when you are loading continuous data.

Best,
Steve Politzer-Ahles

On Fri, Mar 2, 2012 at 7:44 PM, D.rajesh <rajeshlearnstorock at yahoo.com>wrote:

>
>  Hi ,
>
>            I am new to EEG lab and to the subject. I'd like to know what
> is meant
> by 'epoch' in EEG. Isn't the EEG signal is collected continuously in time
> ? Then where
> does the concept of 'epoch' and 'frames' come from and what do they mean ?
>
>
> Thanks and regards
>
> Rajesh.D
>
>
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-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://www.linguistics.ku.edu/
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