MEG reveals correlation between task difficulty and magnitude of the attentional blink

Abstract

In a recent talk (ECVP, 2001) we provided evidence of a plausible neural correlate of the attentional blink (AB) task. This was accomplished by studying the attentional blink (AB) paradigm using whole-head magnetoencephalography (MEG). The AB task presents two targets, T1 and T2, separated from trial to trial by two different temporal lags, as part of a rapid stream of visual information. In our implementation of the AB paradigm, Lag 2 separates the targets by 300 ms and Lag 6 by 900 ms. Target and non-target black letters are presented at fixation, at a rate of 7 items per sec, with the participant required to determine whether 0, 1, or 2 pre-specified targets are presented, then to identify each. The AB is revealed on trials when two targets are presented and, upon successful identification of T1, participants' ability to identify T2 is severely reduced, at Lag 2. Performance at Lag 6 is equivalent to baseline, as established on trials when only T1 or T2 is presented. MEG recording substantiates the behavioural result as it reveals a significant attenuation of neural activity on trials when T2 is presented but unable to be reported, most noticeably in dorso-lateral frontal cortex and in temporo-parietal areas. Activity when T2 can be reported (i.e., no AB occurs) is also attenuated, relative to Lag 6. Moreover, recent analysis has revealed a significant correlation between T1 activity and AB magnitude, suggesting the brain may indeed operate in a limited-capacity fashion.