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Real-Time ERP Index of Attention via SSVEP

By developinginte… on May 27, 2008.

In this poster, Bastos, Mullen and colleagues show that they can analyze electrical oscillations on the scalp of human subjects and predict how quickly they will respond in a simple target detection task. They do this by an interesting method known as the Steady State Visual Evoked Potential (SSVEP), otherwise known as "frequency tagging": the basic idea is that visual stimuli can be flickered onscreen at various frequencies, and that those frequencies are detectable on the scalp - particularly if they are being actively attended.

When the frequency of the flickering stimulus is most strong at electrodes over the parietal and occipital lobes (perhaps enhanced through attention), subjects will subsequently respond more quickly.

Interestingly, they appear to show the opposite effect at a variety of frontal electrodes - greater representation of the tagged frequency yields longer reaction times. The authors don't offer any explanation for this, but one might speculate that enhancement of the tagged-frequency at these frontal sites would indicate subjects were more reactively orienting to the target (thus engaging a widespread orienting system, in frontal and parietal areas), rather than actively-attending (in which the attended frequency is being biased in posterior regions).

Interesting stuff. I'm sure we'll see an interesting paper from this soon...

Tags
cognitive neuroscience

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