What if the part of our brain that we thought was dedicated to visual information also processed other sensory information? Olivier Collignon, a neuropsychology professor, and his team conducted an investigation. The results represent a small revolution for neuroscience.
For 15 years, Olivier Collignon, an FNRS research associate and professor of cognitive neuroscience at UCLouvain, has focused on sensory loss and its consequences for the brain. As head of a research group called the Crossmodal Perception and Plasticity Lab (CPP Lab), he began his research by asking whether the blind develop capacities that exceed those of the sighted to compensate for their lack of vision. Quite recently, the researcher and his team set out on another challenge: studying the brain's perception of moving objects. The results are amazing.
What goes on in our occipital cortex?
The study, published in late May in the scientific journal Current Biology, focused on an area of the brain that processes visual information: the V5 area of the occipital cortex. When we see something move, say, a car, this area activates. When the car is static, the area is much less active. Historically, the occipital cortex has been studied as purely ‘visual’. According to established neuroscience, no auditory or tactile stimuli are processed in this area of the brain. Faced with this unequivocal scientific observation, Prof. Collignon asked: What if this area was also involved in the processing of non-visual information? What if this part of the brain could also process information from another of our senses? To find out, he and his team began with one observation: a moving image is very often accompanied by a sound. So where does the exchange of information between visual and auditory stimuli take place? What if it was in the occipital cortex, in the very early stages of information processing?
An experiment deep within the brain
For five years, in collaboration with the University of Trento (Italy), a UCLouvain team coordinated by CPP Lab PhD student Mohamed Rezk analysed brain activity maps created using magnetic resonance imaging (MRI). Each of 24 volunteer participants were stimulated visually and audibly while lying in a scanner. Moving images in certain directions as well as sounds in the same directions were presented to them. The researchers observed which brain areas became active for sounds and moving images. Using machine learning technology, they could even predict the information sent to participants simply by looking at their brain activity.
Decompartmentalising brain area functions
After analysing all of these brain activity maps, scientists are unanimous: the occipital cortex, initially considered only visual, processes information on moving sounds. However, our brain organisation is highly codified: the area dedicated to visual movement is also involved in auditory movement, but not in the recognition of a person's voice, for example. ‘Even more precisely,’ Prof. Collignon explains, ‘we noticed that each direction of movement had particular representations in the brain. The area that prefers to answer “to the right” for the visual direction also prefers to answer “to the right” for hearing. For our brain, the important thing isn’t the type of information (visual or auditory) but its function: What should I do with this information?’
A small revolution for neuroscience
This conclusion has caused quite a splash in the scientific world. Indeed, a cerebral area long perceived as solely visual is in fact not impenetrable to information from other senses. This finding is categorically opposed to classical neuroscience, which teaches that certain parts of the brain are unimodal and sensory information processing is compartmentalised.
‘This discovery opens up an incredible field of possibilities,’ Prof. Collignon says. In addition to this comprehensive study, CPP Lab members worked on other, more specific study elements (see boxes). In the years to come, Prof. Collignon will map connectivity between sensory areas, exploring for paths where information is transferred between sensory areas. ‘We also want to understand the link between the brain’s multisensory organisation and the mechanisms of transmodal plasticity that’s expressed in the event of sensory deprivation’ (see Box 1). These are all questions to which UCLouvain researchers hope to find answers. Because a scientist isn’t satisfied with hypotheses.
A glance at Olivier Collignon's bio
After earning a master’s degree in psychology from the University of Liège and a master’s degree in cognitive science from UCLouvain, Olivier Collignon specialised in cognitive neuroscience, completing a PhD at UCLouvain on cerebral plasticity in case of blindness. He has pursued this subject throughout his career, including during two postdocs at the Université de Montréal’s Centre de recherche en neuropsychologie et cognition. Since 2012, he has led a UCLouvain research group called the Crossmodal Perception and Plasticity Lab (CPP Lab) and served as an associate professor at the University of Trento’s Center for Mind and Brain Science (CIMeC). Since 2016, he has been an FNRS research associate and associate professor at UCLouvain. His research is funded by multiple UCLouvain sources (e.g. FSR, Louvain Cooperation), the FNRS (e.g. MIS, EOS), and European sources (e.g. ERC Grant, Marie Curie). His research focuses on the general question: How does a brain area develop, maintain and change its sensory and functional role?