Why EEG trials recoded for same stimulus is different? For example, the same visual stimulus like 12hz ssvep produces comparable but unique timeseries.
Other than noise, under ideal conditions, should the eeg trial be same?
Hi Sai,
The amplitude of SSVEP signals can be modulated by subjects' attention. So as the subject's attention fluctuates during the experiment, you will see SSVEP amplitude change.
Though I believe that the single trial variability mostly come from, except measurement noise and various artifacts, changes in background activity which can be influenced by your alertness, fatigue, mind wandering etc.
The EEG frequencies are continuously modulated by fluctuations of vigilance.
Agreed with Wolfgang and Sheng-Hsiou. EEG is always changing based on the individual subject and their alertness, fatigue etc. Some trials they may get into a flow and even process more passively than actively. Passive vs active attending to the same stimulus has been repeatedly shown to modulate EEG. In general, this is why it is important to take averages of many trials in order to get the best representation.
In addition, neurons populations don't always fire at the same rate, even responding to a same stimulus in several trials.
At the moment of stimulation, for example visual stimulation of the brain, are we just doing a stimulus that is being processed? In my opinion, because the brain is processing simultaneously, these processes are being carried out in parallel or in series. These processes are responding to internal or external stimuli or even within the brain's network. , Your stimulation will also be one of a series of processes, in my opinion the difference in response to the stimuli may be due to the fact that when your brain is stimulated you may have different brain processes at the moment of stimulation.
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