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Posts Tagged ‘Neurosciences’

« The colors we see, the words we read, the music we play and listen to – in short, our entire sensory experience is part of the brain’s attempt to create a stable environment that we can understand. Our individuality, our subjectivity is a direct consequence of this sensory world the brain creates. » Israel Rosenfield

Photo credit : Keke Keukelaar

Israel Rosenfield and a small group of neuroscientists discussed the role of the brain in determining our relation to the world. The debate, held at the Institute for Public Knowledge on April 12th gathered hundreds of people who were curious to learn more about the possibilities that the brain offers.

If you missed the event, find below the panelits’ essays :

What does the brain do? By Israel Rosenfield (le texte traduit est disponible ici)

Pleasure and Pain and the Physical Brain, by Edward Ziff ( Le plaisir, la douleur, le cerveau physique )

How the brain may work, by Roberto Llinas.

Find also Sue Barry’s essay and other approaches to the topic in previous posts.

Revivez l’expérience des neurosciences grâce à Claire Richard.

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Crédit photo : Keke Keukelaar

C’est bien connu, pour nous tous, la connaissance découle de l’expérience. Reste à savoir ce qu’on entend par expérience. En anglais comme en français, le mot désigne deux choses très différentes.

Expérience : épreuve destinée à vérifier une hypothèse, ou à étudier des phénomènes.

Microscopes, éprouvettes, scanner, électrodes. synapses, neurones, protocoles, résultats reproductibles.

Et aussi  :

Expérience : fait vécu.

Conscience, représentations, langage et chair, puis récit, récit, la mise en mots de l’expérience.

Deux façons d’appréhender la connaissance et le monde – d’un côté l’objectif, de l’autre le subjectif, d’un côté la science, de l’autre les arts, d’un côté les chiffres et de l’autre la parole.

En ce qui concerne le cerveau, d’un côté les neurosciences, de l’autre la psychologie ou les arts.

Mardi 19 avril, dans une salle bondée de Cooper Union, les invités ont démontré qu’entre les deux types d’expérience il n’y a pas à choisir. L’expérience vécue accompagne et nourrit l’expérience scientifique,  lui suggère les questions à creuser et les directions à suivre.

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All participants to this remarkable panel have amazing stories to tell and deep insights into how the brain creates mind. I will focus on Susan Barry’s experiences because they are remarkable and very interesting. Her book challenges the opinion of those who insist that the brain is strongly genetically determined and static after a critical period of development. Her book also provides concrete challenges for researchers like myself who try to understand how the amazing plasticity of our human brain is possible.

My own perspective is that of a roboticist and AI researcher, trying to understand perception, conceptualization and language by building operational models and doing experiments with robots interacting with each other in language games. Neuroscientists or philosophers often critize this approach but understanding some aspect of nature by building models is a path to knowledge that is as effective as pure observation. Moreover mental capacities cannot be simply reduced to neurobiology, partly because the body, the ecological environment and other individuals play a big role in shaping how we see the world, think and act, and partly because mind and culture form an emergent level of their own.

Susan Barry’s tale describes how she was able to regain 3D vision at a late stage in life. Being a keen observer and a neuroscientist herself, she interweaves her narrative with many deep insights into the brain in general and vision in particular. Let me comment and amplify some of her observations.

A first important insight coming out of her experience is that the brain is not a strictly modular system. Usually there are many differentstrategies for handling an important function and all possible sources of knowledge are brought to bear as quickly as possible to the task. This is what makes the brain so robust, adaptive and flexible. We have learned the same lesson in building vision systems for autonomous robots. Robots need this for navigation, grasping objects, or for communication, for example to understand a request like « Pick up the block behind the box ». Many systems for stereo-vision have been devised using two cameras. But then a hugely complex collection of information processing must still take place. Images from the two eyes must be compared to make an estimate of the depth of each point in the visual field using basic geometry. It turns out that this is already an extraordinary achievement and requires substantial computation. The visual process must find back which image points (usually called pixels) in the right and left image correspond to the same object in the world and this in turn already engages highly complex processes for segmenting the world. Segmentation and object recognition must rely on many strategies, for example based on color, shading, texture, coherent movement, etc. and even then top-down predictions on an object’s appearance need to be combined with bottom-up information flow to identify and track objects, particularly if they are moving or the observer is moving. Our robotic systems use also other methods for depth perception which do not rely on having two cameras. Specifically, we have been using a system that exploits knowing the morphology of the body, the particular positions of the torso legs, and head as well as an hypothesis about the ground, in order to establish at least the relative position of objects in space. This works just as well, so much so that some of our robots take the form of a one-eyed cyclops.

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Sue Barry…

… was with us at the IPK on tuesday night. Here is the essay she wrote for the panel « What Does the Brain Do? »

Born severely cross-eyed, Barry takes us on her journey toward binocular vision. Beyond the physical change from turning her head to suppress the vision of one eye at a time, she explains the experiential shift and emotional change of seeing in three dimensions.

Photo credit: Keke Keukelaar

One common approach to studying the brain is to examine the consequences of brain injuries.  If an individual suffers a stroke, for example, and loses the ability to speak, then the damaged area of the brain may play a role in language.  A second, perhaps less common, strategy is to study the process of rehabilitation following a brain injury or disorder.  As I will illustrate in this talk, the type of therapy and amount of practice involved in successful recovery provides insights into the fundamental functions of the brain.

 For the past century, conventional wisdom held that the adult human brain is largely immutable.  Most of its circuitry is laid down by early childhood with little possibility for rewiring in adulthood.  Great emphasis has been placed on the role of “critical periods” in early life for the development of basic perceptual and language skills.  Once these critical periods were passed, little neuronal reorganization was thought possible.

For example, the scientific and medical communities have long cited a common childhood condition, strabismus (crossed eyes or wall eyes), as a classic example of a developmental disorder that causes permanent changes in vision if it is not “corrected” within a critical period in early childhood.  Surgeons may attempt to cosmetically straighten the crossed eyes of a child, but, unless the surgery is performed before the age of two, the chances of the child developing stereopsis or 3D vision are only twenty percent1.  Moreover, experiments done on infant animals made artificially strabismic indicate that these animals do not develop the binocular neurons necessary for normal stereopsis and depth perception.  Hence, an adult patient, strabismic since infancy, has been considered permanently stereoblind.

 This was my story.  I had developed infantile esotropia (crossed eyes) in the first months of life.  After three surgeries when I was 2, 3, and 7 years old, my eyes looked more or less straight, but I lacked stereopsis.  I could not see the 3D in 3D movies.  As a neurobiology professor, I lectured on the development of the visual system, discussed the concept of critical periods, and often used my own history as an example of how well theory fit reality.

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