[Eeglablist] A question about the averaging for the P300 Speller

[Ettore Coppola]

Thank you for your answer!
The problem is to average epochs target with epochs no-target; in the 
online, I don't know if an epoch is target or no-target; so, if a average 
epochs, I average together target and no-target.
I checked in the literature and I didn't find anything.
Thank you
Ettore


-----Messaggio originale----- 
From: Arnaud Delorme via eeglablist
Sent: Wednesday, November 30, 2022 2:40 AM
Cc: eeglab list
Subject: Re: [Eeglablist] A question about the averaging for the P300 
Speller

> Sorry for my bad English!
> A question about the averaging for a P300 work.
> The P300 Speller has  a 6 x 6 matrix of characters. Each row and each 
> column are intensified by the system; the intensifications are presented 
> in a random sequence.
> The user focuses attention on one of the 36 cells of the matrix, with the 
> row and the column containing the character to be communicated 
> constituting the rare set (target) , and the other 10 intensifications 
> constituting the frequent set (no-target).
> In a first phase we go to train the classificator: in this phase the 
> system knows if every epoch is  target or  no-target.
> In the online phase, when the user tries to select a character, the system 
> doesn’t know if an epoch is target or no-target.
> In this situation, the  online phase, is useful to average epochs?

You can average epochs or probably better classify each epochs and then use 
a voting mechanism. You might want to check in the literature what makes the 
most sense.

Best wishes,

Arno

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