Talk:Event-related potential

Suggestion to merge in related page with this one

please see suggestion to merge the "evoked potential" page into this page [1] —The preceding unsigned comment was added by Robert p levy (talk • contribs) 01:56, 2 February 2007 (UTC).<! This is not a good idea, since evoked potentials are but a limited class of the brain responses assciated with voluntary movements and cognitive processes, including language processing. This change would reduce the scope of human brain responses that can be extracted from the electroencephaoogram by event-related averaging and other methods. This topic should embrace the broadest range of electrophydiolical manifestations of spcific human brain processes. The term "event related poentials (ERPs) meets this criterion, whers "evoked potential" does not t

Typo?

I do not get the sense of this sentence: "... the brain response to a single stimulus or event of interest is usually visible in the EEG recording of a single trial; to see the brain response to the stimulus, the experimenter must conduct many trials..." I guess that "not" is missing in the first part of the sentence.—Preceding unsigned comment added by 195.113.187.94 (talk) 13:25, 24 February 2009

Fixed. 13:58, 24 February 2009 (UTC)

Same as evoked potential?

In the course of taking a neuroanatomy course we learned that Event-Related Potentials are "brief changes in EEG signals in response to discrete sensory stimulus". According to eMedicine "Evoked potentials are the electrical signals generated by the nervous system in response to sensory stimuli". They each indicate that they are responses to sensory stimuli. Thus I am confused as to how they differ and, moreover, the reason for two distinct articles. Thoughts? Basket of Puppies 00:37, 29 June 2009 (UTC)

In real life, a lot of people use them more or less interchangeably (with the general idea that "evoked potential" is an older word for "event-related potential"). Actually there is a difference, but it's a bit confusing. "Event-related potentials" are a tbroad group of effects, and include both "evoked potentials" and "induced potentials". Evoked potentials are the subject of by far the most research (at least in my field, neurolinguistics); there are only a few articles out there discussing induced potentials. WP currently has no article on induced potentials (and its articles on event-related potentials and evoked potentials both need a lot of work, as well.

The difference is more or less this. Evoked potentials are electrophysiological components (ie, peaks and valleys in the EEG squiggle) that are time-locked to the onset of a stimulus. In other words, you play 1,000 beeps to a person, and take a picture of the potential that happens after every beep; then you take each of those pictures and put them on top of one another, so that the time when the beep happened is the same in every one (this is the time-locking), and average them together, and what is left is an evoked potential: an average of all the electrophysiological activity, with respect to the onset of the stimulus.

Induced potentials, on the other hand, are also electrophysiological components, but they are time-locked to the component itself (could be its peak or its onset) rather than the stimulus. In other words, you play all those beeps and line up all the pictures, but instead of making them line up on the stimulus, you make the components themselves all line up—in trial 12 the component might have happened at 75 milliseconds, in trial 89 it might have been 90 milliseconds, etc. The averaged waveform you get is an induced potential. The idea behind this is that some brain responses are a bit "wiggly"—they don't always happen at the same speed relative to their stimulus—and thus don't show up in evoked potential analysis (since they don't all peak at the same time, they get "averaged out"). Induced potentials, supposedly, might allow us to investigate some ERP components that we have been ignoring for a couple decades because we were focused on evoked potentials. (At least, that is what you will hear from people who believe induced potentials are a promising new field.)

If there are any inaccuracies in this description, hopefully someone else watching this page can clarify things. rʨanaɢ ^talk/_contribs 01:38, 29 June 2009 (UTC)

Ok, after reading this a few times I think I now understand. I am actually tempted to discuss this further with my neuroanatomy prof. Thanks for the speedy reply, Rjanag! Basket of Puppies 02:22, 29 June 2009 (UTC)

Heh, I don't fully understand induced potentials, either :). Another interesting distinction similar to this one is the distinction between time-domain analysis and frequency-domain analysis, which your professor might bring up when you talk to him/her. (The simple, cartoon explanation is that you generally use time-domain analysis to look at evoked potentials, and frequency-domain analysis to look at induced potentials. Basically, in time-domain analysis you are interested in activity happening at different times—for example, the N400 versus the N100 versus the ELAN—whereas in frequency-domain analysis you are interested in activity happening in different frequency ranges, regardless of what time it happens.) rʨanaɢ ^talk/_contribs 02:44, 29 June 2009 (UTC)

"ERPs are measured with EEG"

They can (and frequently are) measured via electrocorticograms (ECoG), which is basically an EEG performed underneath the skull. This absolute statement might want to be widened. (See, for example, "A Direct Brain Interface Based On Event-Related Potentials" by Levine, 2000.)