Inside the brain of the profoundly deaf


The brain is divided into areas, each of which processes specific information. If a certain type of information is missing – such as sounds – the brain reorganises itself... but not at random!

We have various areas in the brain which are intended to process specific types of sensory information. For example, visual information is managed at the back of the brain; voices are processed in a lateral region behind the ear, and so on. But what about people who are blind or deaf from birth? Is the cerebral area that is supposed to handle the missing information left inactive and redundant?

Plasticity: when the brain adapts

‘No, because the brain adapts to sensory deprivation by reorganising itself,’ says Professor Olivier Collignon, FNRS researcher and associate professor at two UCL institutes, IPSY and IoNS (1). ‘It's what’s known as “crossmodal” plasticity, a process thought to compensate for sensory deprivation. When a brain area does not receive the information it is supposed to receive, it becomes “colonised” by other types of information. The brain area that is deprived of its particular sensory information then starts to process information coming from other senses.’

Professor Collignon and his colleagues at the University of Trento in Italy have investigated the cerebral plasticity of people with profound deafness. For six years, using fMRI and magnetoencephalographic imaging, they studied and compared the brain activity of the profoundly deaf and hearing people. Their findings were published in the prestigious American journal PNAS (2).

Faces in place of voices

In particular, the researchers found that this reorganisation of the brain is far from random. ‘We’ve demonstrated that facial recognition, which involves a particular type of visual information, activates the brain area normally used for voice recognition,’ explains Professor Collignon. This is hardly surprising, as these two systems are used to work together. After all, we pick up a lot of information from a face – a person’s identity, age, sex, emotions, and so on – which are usually consistent with that person’s tone of voice. And when we talk to someone, especially in a noisy setting, we read their lips without even realising it.

‘There is therefore a natural “highway” between the cerebral area for voices and the area for faces,’ continues Professor Collignon. ‘It’s a bit like the E40 motorway linking Brussels and Liège. Suppose Liège (standing for voice recognition) is emptied of all its inhabitants (i.e. voices). Not only will people from Brussels (i.e. faces) continue to drive on the E40, but in addition, some of them will go and live in Liège, thus keeping the area active!’

Research implications and prospects

The findings of this study open up some interesting prospects. ‘From the point of view of fundamental research, we can confirm that the brain's architecture is not immutable: the brain is organised according to our experiences. At the same time, this adaptability obeys certain functional principles. It is not the case that any kind of information will colonise any region of the brain. There are certain rules – natural links between the areas of the brain that affect cerebral plasticity.’

This discovery could also have clinical applications. What happens when the profoundly deaf gain hearing after a cochlear implant, for example? Is introducing auditory information into an area now used for the processing of faces likely to cause interference, or, on the contrary, promote the new capacity to hear? ‘That’s the big question! The cochlear implant doesn’t work every time and at present it's hard to predict the patients for whom this technique will be a success or a failure. This variability may be related to “crossmodal” plasticity. The next step in our research is therefore to find out the extent to which this plasticity can be an asset and/or an obstacle to the introduction of auditory information into the brain of a given patient.’

Candice Leblanc

(1) The Institute for Psychological Research (IPSY) and the Institute of Neuroscience (IoNS)

(2) S. Benetti et al., ‘Functional selectivity for face processing in the temporal voice area of early deaf individuals’ in Proceedings of the National Academy of Science, May 2017.


  A glance at Olivier Collignon's bio

                                     Olivier Collignon

                                   2001 Master’s in psychology, University of Liège (ULg)

2004 Master’s in cognitive sciences, Catholic University of Louvain (UCL)

2006 PhD in psychology, specialising in neuroscience, UCL

2006-10 FNRS postdoctorate, Neuropsychology and Cognition Research Center, University of Montreal (Canada)

2007-11 Lecturer, Department of Psychology, University of Montreal

2010-12 Researcher, Sainte-Justine University Hospital Research Center, Montreal

Since 2012 Head of the Crossmodal Perception and Plasticity Lab Research Group and assistant professor at the Center for Mind and Brain Science (CIMeC) of the University of Trento (Italy)

2014 National scientific qualification (university school teaching qualification) in Italy

Since 2016 FNRS associate researcher and associate professor, UCL

Professor Collignon’s research is mainly funded by the FNRS, an ERC-Starting grant (MADVIS) and UCL. The study of cerebral plasticity in the deaf was entirely funded by CIMeC at the University of Trento.




Published on August 29, 2017