Your Brain Is A Cartographer

The concept that the brain holds maps of the surface of the body in the primary sensory and motor cortex is a fascinating but well known fact to the field of neuroscience since the early work of Wilder Penfield. What is less broadly appreciated is the concept of “peripersonal space”. A new book by Sandra and Matthew Blakeslee describes peripersonal space in the following way:

The maps that encode your physical body are connected directly, immediately, personally to a map of every point in that space and also map out your potential to perform actions in that space. Your self does not end where your flesh ends, but suffuses and blends with the world, including other beings. […] Your brain also faithfully maps the space beyond your body when you enter it using tools. Take hold of a long stick and tap it on the ground. As far as your brain is concerned, your hand now extends to the tip of that stick. […] Moreover, this annexed peripersonal space is not static, like an aura. It is elastic. […] It morphs every time you put on or take off clothes, wear skis or scuba gear, or wield any tool. […] When you eat with a knife and fork, your peripersonal space grows to envelop them. Brain cells that normally represent space no farther out than your fingertips expand their fields of awareness outward, along the length of each utensil, making them part of you.

What I appreciate about this, besides the stretchy comic book characters that it makes me think about, is that it provides a powerful perspective to begin piecing together a mass of disparate neuroscience data, which the Blakeslee’s capitalize on.

You’ll recognize the name Sandra Blakeslee from her co-authorship with Jeff Hawkins in On Intelligence and with V.S. Ramachandran in Phantoms in the Brain. This new book continues in the spirit of illustrating the broader significance of surprising findings in neuroscience. It covers a lot of recent neuroscience research, including mirror neurons, place cells and grid cells, the insular cortex and neuroprosthetics. For anyone looking to get the quick picture of these frontier research areas, this book serves as an excellent primer. It does an excellent job of making connections to socially relevant topics such as the secrets of athletic excellence, underlying causes of eating disorders and the modern obsession with plastic surgery. I have come to believe that neuroscience will eventually provide concrete explanations for the metaphors we use and the spooky phenomena we believe in but science cannot prove. Along those lines, this book does a great job of describing brain mechanisms that may underly paranormal phenomena like auras and out-of-body experiences.

One of my favorite parts is chapter six, a short chapter with a Phantoms in the Brain feel that presents some extremely jarring clinical examples of neurological problems potentially caused by body map disorders. It describes cases of individuals who want to have their limbs amputated because they feel like they don’t belong to them, individuals who no longer get feedback from their limbs as if they have disappeared, as well as cases of one woman who felt like she had three arms and three legs. That these cases exist are fascinating in their own regard; that there exists a systems-level conceptual framework with which we might understand the underlying causes for them is utterly incredible.

The implications of these ideas to AI are significant. What kinds of intelligent systems can we build by assuming that they have ego-centric representations of objects in their peripersonal space, or by assuming that their motor intentions are tickled by watching the movements of other creatures? The implications for computational neuroscience are also significant. What kind of system of neuronal processors is capable of producing cells that are sensitive to peripersonal space? What information must flow into those cells, and where is that information available from in the brain? Along what channels and using which “algorithms” does your brain map the visual information of a person moving their limbs to the motor areas that control your limbs? Perhaps I’ll be able to read about these things in the next Blakeslee neuroscience tour de force.

The Body Has a Mind of Its Own: How Body Maps in Your Brain Help You Do (Almost) Everything Better
by Sandra Blakeslee (Author), Matthew Blakeslee (Author)
Random House Publishing Group

(Full disclosure: Sandra Blakeslee and Random House kindly sent us a copy of the book to review before their release date…thanks guys!)

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