Lau Møller Andersen
CNRU - Cognitive Neuroscience Research Unit
"Spatio-temporal localization and task specificity in the search for neural correlates of perceptual consciousness"

Opponents:

• Talis Bachmann, Tartu University
  http://www.bachmannlab.com/
• Hartwig Siebner, Hvidovre Hospital
  http://www.drcmr.dk/siebner

English summary:

What consciousness is is one of the perennial questions that have vexed human beings throughout known history. In this dissertation, I have used magnetoencephalographic recordings to investigate what happens in the brain when one becomes conscious of a visual stimulus. I have also investigated how one can manipulate when and how one becomes conscious. It might seem self-evident that occipital activity is what makes us become conscious of visual stimuli, but many theories regard frontal activity as crucial for becoming conscious of stimuli. Based on 3 experiments and an opinion article, I found that occipital activity best explained the differences in perceived clarity that participants reported. My analysis of the magnetoencephalographic data was based on multivariate analyses since, as we argue in the opinion article, they are more sensitive than traditional univariate analyses are to how consistently spatio-temporal patterns of neural activity correlate with changes in perceptual consciousness. In experiment 1, I found that perceived differences in perceptual consciousness were best explained by occipital activity during an early range (~130-300 ms). This might lead one to believe that exactly this spatio-temporal activity could by itself explain the becoming conscious of visual stimulation. Experiment 2, however, showed that one's theory must be more nuanced, and that task requirements and cognitive strategies influence the timing of activity and which activity that can explain differences in perceptual consciousness. Experiment 3 showed that top-down expectations and sensory saliency changed how informative different levels of perceptual consciousness were, and that participants have insight into when they are in an informative state or not, no matter how minuscule the amount of information is.

Altogether, I have found evidence that the occipital lobe is the most important area for realizing visual perceptual consciousness, but that the exact timing and the involvement of other brain areas depend on the availability of cognitive strategies and how informative one's perceptual state is. 

ALL ARE WELCOME