CCNCS Seminar Details
Ongoing Brain States Predict Conscious Access: A Discussion of Evidence using EEG and the Attentional Blink
|Speaker:||Hannah L. Pincham & Dénes Szücs|
|Date/Time:||Wednesday 2 November 2011, 4.15pm|
Neuroscience explanations of conscious access typically focus on neural events elicited by stimuli. In contrast, event-related brain potentials can be used to examine whether the ongoing state of the brain before a stimulus can determine both conscious access and the post-stimulus neural events associated with consciousness. The 'attentional blink' paradigm represents an ideal phenomenon to investigate prestimulus contributions to consciousness because the second, critical target in this paradigm only reaches consciousness on a proportion of trials - despite identical stimuli being employed across trials. In the current experiments, we asked participants to detect two target letters from digit distractors whilst their brain activity was being recorded. Trials were classified based on whether the second, critical target (T2) was detected. Interestingly, T2-detection was pre-determined by brain activity prior to the onset of the stimulation stream. Specifically, neural activity associated with T2-detected and T2-undetected trials began to diverge more than 400msec before the stimulations stream was presented. Accurate T2 detection was also accompanied by enhanced post-stimulus neural activity, as reflected by a larger P3b component. Furthermore, prestimulus and post-stimulus markers of T2-detection were highly correlated with one another suggesting that ongoing states of he brain can predict post-stimulus neural activity. Therefore, conscious experiences are likely shaped by potentially random fluctuations in neural activity. Overall, it appears that conscious access is underpinned by an important relationship involving predictive prestimulus neural activity and responsive post-stimulus brain activity.