Understanding Blindsight: An Interview with Dr. Beatrice de Gelder

(Editor’s note: This article from a past issue of Brain World magazineIf you enjoy this article, consider a print or digital subscription!)

BW: What part of the brain is responsible for the unconscious recognition of emotions?

BDG: In a patient who is cortically blind, the visual information comes normally into the eyes, but rather than reaching the visual cortex it diverts to other lesser-known visual pathways. Our major interest is to trace these pathways. Then we might also find that such alternative pathways are also functional in normal individuals. Even people who can see normally may use a number of alternative pathways specialized for a specific range of functions.

BW: How can blindsight be related to a sixth sense?

BDG: It is of course hazardous to make that connection. What we are working on is not the sixth sense in any mysterious way, but I can see why people make the link, in the sense that there are these phenomena that we don’t understand that still exist. Blindsight is simply based on the ability of alternative visual routes that are not accompanied by consciousness and are still poorly understood. So we have to separate the discussion. Is blindsight about a sixth sense? The answer is no. Blindsight is simply about the multiple origins and functions of the visual system, which we have traditionally underestimated. About a sixth sense, that is not really our field. Still, at a very general level, many will agree that there are untapped resources in the brain.

BW: The amygdala has long been viewed as having an important role in emotions and as an interface between cognition and emotion. Have you found any relationship between the amygdala and blindsight?

BDG: We have systematically found that in most cases there is amygdala activity when a cortically blind person is shown emotional stimuli. We have this same finding again in our most recent studies with bilaterally blind patients that we are about to submit and publish. So there is no doubt that the amygdala reacts to unseen emotional stimuli. For this reason, cortically blind people with amygdala damage or who had their amygdala removed are impaired to perceive emotions. I worked with this type of patient in South Africa and found out that they would still keep their blindsight to movement and geometrical figures, among others.

BW: You mentioned a new study that you are about to publish. Could you tell us about it?

BDG: We have one study done with our Geneva colleagues to be published soon. It shows that bilaterally blind patients can discriminate the direction of gaze and faces looking straight, left, or right. It also explains that there is clear amygdala activation when a person is staring directly at them. Knowing that someone is staring at you is a biologically strong system. We are all, of course, very sensitive to that.

BW: How can the findings on blindsight contribute to treating patients with problems in their visual cortex ?

BDG: We work with cases that are extremely rare. Some patients are unilaterally [one hemisphere], or bilaterally [both hemipsheres], blind. The cortically blind can make use of their unconscious visual ability, like you and I do all the time, but it is just that these people do not have the conscious experience of seeing, so they stop trying to see or do things.

BW: What is the training for improving blindsight?

BDG: My colleague in Aberdeen has developed a computer-based training involving visual exercises with feedback provided, and the patient has to do these exercises every day, for a substantial amount of time. After a while, there is substantial reduction in the visual-field loss. For this reason, it is important to select dedicated patients, because improvement is slow and it is not spectacular. In some cases the unconscious visual abilities get better, and in others the blindsight stays as it is. So it all depends, because not all cortically blind patients display blindsight. We are now also developing new techniques, involving, for example, virtual reality environments — crossing the street navigating a virtual reality. That is what I was doing this morning. I was preparing an experiment for a patient who is coming in April. He is going to navigate a virtual room with obstacles on his path, but where there is, of course, no risk of hurting himself.

BW: You have stated that people with autism and schizophrenia are able to recognize faces but not always emotions. How can your findings on blindsight help these patients?

BDG: Yes, that is another area of our work. For this research we are lucky that we have more cases. We continuously recruit people with face-recognition difficulty. This is also a good example of something we didn’t understand some decades ago. Some people were blamed for being asocial, arrogant, or absent-minded, and it is just now that we begin to understand that face recognition is just a skill in the brain that these individuals lack.

Sometimes the comparison is made between people with face-recognition problems and people with autism. But in a way, these are opposite things. People with autism can recognize a person’s identity without understanding, processing, or perceiving the full extent of the emotional expression.

BW: How do you see advances in the study of blindsight 20 years from now?

BDG: There will be more findings in this field, with better case studies and important insights from animal research. It is important to remember that a major input for understanding blindsight comes from monkey research. This allowed discovering that training could build up the blindsight skills after damage to the visual cortex. It is just a pity that we only have a few human cases, as it allows the ones who want to criticize this kind of research to do so. Most people agree that we have unconscious abilities, but when it comes to studying the visual system, the large majority of vision researchers still focus on the visual cortex.

What should also change in the following 20 years is that clinicians become more aware of this phenomenon of nonconscious perceptual abilities. The most important reason why we do not have more patients is because they do not get referred to us from the clinic. If a patient had a stroke, they tell the person that he/she is blind, and that is the end of the story. In the case of face recognition, people are more aware, as there have been more articles in the last 10 years on face-recognition problems even in otherwise neurologically typical adults. So people write to us almost every week, describe their longstanding problems with faces, and we bring them to the lab; but the first contact for patients is, of course, with the clinical neurologist.

BW: How can your findings in neuropsychology contribute to creating a healthier, happier, and more peaceful society?

BDG: There are many areas where better knowledge increases people’s chances for good health. We are working very hard and trying to do the most possible to understand and improve the condition of patients with brain damage, for instance. Surely scientists are basically motivated to pull at the veils of ignorance that still cover most of the workings of the human brain. It is marvelous to work with our patients, because they are very motivated even if it is entirely clear that they have nothing concrete to gain from participating in our studies. So in general, a broader and richer picture of the mind and its brain must lead to having a better understanding of human nature, and this is important to creating a happier, healthier, and more peaceful society.

(Editor’s note: This article from a past issue of Brain World magazineIf you enjoy this article, consider a print or digital subscription!)


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