Marian Schneider: Relating human conscious perception to the brain at unprecedented spatial resolution
“We’ve been researching a very old question: how can we link our daily experiences to underlying brain activity?”
Marian Schneider joined the ‘Visual processing’ group, led by Prof. Rainer Goebel, almost 5 years ago. Around that time the hype of the ultra-high field MRI scanners at FPN (Faculty of Psychology and Neuroscience), and what they could do was growing quickly. From that time, it was possible for researchers to use the facilities at Scannexus to digitally map the brain on a high, sub-millimeter, resolution. “This means you can study brain responses at an unprecedented level of detail.”
Columns in the brain
“For this research we were interested in columnar structures.” On the left and right side of the brain there are special areas for processing visual motion. When you see something move, certain areas of the brain become active. These areas are called the Human Motion Complex, and they always activate when you see motion. “The interesting thing originally found in monkeys is that we can split this area into smaller columns. Each of these columns reacts to different directions of motion.” Schneider and his colleagues have now found that the same is true in humans confirming also earlier findings in the Goebel lab. So, a distinct part of the Human Motion Complex activates when you consciously perceive vertical motion, and a different part for horizontal motion. “We were only able to find this because of the ultra-high field MRI scanners.”
A question Schneider wanted to answer was: does activation in cortical columns of the motion complex relate to retinal stimulation (physical input to the brain) or does it relate to the generated conscious percept (making sense of what is happening). To make sure he could know the difference between these activations, test subjects were shown ambiguous apparent motion stimuli that could be perceived as either horizontally or vertically moving. This way, if the area’s horizontal columns get more active when the subjects report perceiving horizontal motion and the vertical columns when the subjects report perceiving vertical motion, Schneider would know that the area activated due to the constructed conscious percept.
The bigger implication of these findings is that there are more areas that are specific for different things in the visual world: faces, houses, letters. Those areas might have sub-areas as well (i.e. specific columns for individual letters or face features, such as eyes, noses and mouths). “This also shows that there is a compositional element to our consciousness.” How we perceive the world around us is a composition of tiny factors all working together to create a single image that we can make sense of. “We have now been able to clarify one little part of the entire puzzle.”
“Our work is an important breakthrough for better understanding neural correlates of consciousness at an unprecedented level of detail in the human brain. It is the kind of exciting detailed finding that I hoped to be able to discover at the time when Maastricht University decided to acquire the Scannexus ultra-high field MRI scanners.”
Rainer Goebel, Professor of Cognitive Neuroscience
Goebel’s team is working on building a multi-area brain model of human visual perception, cognition and action in the context of the Human Brain Project (HBP). In this ambitious project, the developed brain model is not only simulated in the computer but controls humanoid robots in a closed-loop embodied system. To ensure that the operation of the brain model is indeed emulating what the brain is doing, detailed knowledge of how the human brain functions is needed. Schneider’s work brings this ambitious project one step further by providing crucial insights about how the human brain constructs meaningful unambiguous conscious precepts from ambiguous physical input data.