Dædalus coming up in Dædalus: On an Aging Society John W. Rowe, Jay Olshansky, Julie Zissimopoulos, Dana Goldman, Robert Hummer, Mark Hayworth, Lisa Berkman, Axel Börsch-Supan, Dædalus Dawn Carr, Linda Fried, Frank Furstenberg, Caroline Hartnett, Martin Kohli, Mauricio Avendano, John Rother, David Bloom, David Journal of the American Academy of Arts & Sciences Canning, and others Winter 2015 On Water Christopher Field & Anna Michalak, Michael Witzel, Charles Vörösmarty, Michel Meybeck & Christopher L. Pastore, Terry L. Good For? Winter 2015: What is the Brain Anderson, John Briscoe, Richard G. Luthy & David L. Sedlak, Stephen R. What is Fred H. Gage Neuroscience: The Study of the Carpenter & Adena R. Rissman, Jerald Schnoor, Katherine Jacobs, and the Brain Nervous System & Its Function 5 others Good For? Robert H. Wurtz Brain Mechanisms for Active Vision 10 Thomas D. Albright Perceiving 22 Food, Health & G. David Tilman, Walter C. Willett, Meir J. Stampfer & Jaquelyn L. the Environment Jahn, Nathaniel D. Mueller & Seth Binder, Andrew Balmford, Rhys A. J. Hudspeth The Energetic Ear 42 Green & Ben Phalan, G. Philip Robertson, Brian G. Henning, and others Larry R. Squire Remembering 53 & John T. Wixted The Internet David Clark, Yochai Benkler, Peter Kirstein, Deborah Estrin & Ari Brendon O. Watson Sleep, Memory & Brain Rhythms 67 Juels, Archon Fung, Susan Landau, John Palfrey, and others & György Buzsáki Emilio Bizzi A Hard Scienti½c Quest: plus What’s New About the Old?; Political Leadership; New Dilemmas & Robert Ajemian Understanding Voluntary Movements 83 in Ethics, Technology & War &c Joseph E. LeDoux Feelings: What Are They & How Does the Brain Make Them? 96 Earl K. Miller Working Memory Capacity: & Timothy J. Buschman Limits on the Bandwidth of Cognition 112 Terrence J. Sejnowski Consciousness 123 U.S. $14; www.amacad.org Cherishing Knowledge · Shaping the Future Inside front cover: The receptor for auditory stimuli, the organ of Corti, includes a single row of inner hair cells that convey information about sound to the brain. The three adjacent rows of outer hair cells constitute a mechanical ampli ½er that increases the ear’s sensitivity and sharpens its frequency tuning. In this confo- cal micrograph of the mouse’s cochlea, both green and red labels distinguish the hair cells. The nuclei of all the cells, including the arcs of cells bracketing the hair cells, are marked with a blue dye. © 2015 by Ksenia Gnedeva. Fred H. Gage, Guest Editor Phyllis S. Bendell, Managing Editor and Director of Publications D Peter Walton, Assistant Editor Emma Goldhammer, Senior Editorial Assistant J Committee on Studies and Publications Jerrold Meinwald and John Mark Hansen, Cochairs; Denis Donoghue, Gerald Early, Carol Gluck, Sibyl Golden, Linda Greenhouse, John Hildebrand, Jerome Kagan, Philip Khoury, Steven Marcus, Eric Sundquist, Jonathan Fanton (ex of½cio), Don M. Randel (ex of½cio), Diane P. Wood (ex of½cio) Dædalus is designed by Alvin Eisenman. Dædalus Journal of the American Academy of Arts & Sciences The labyrinth designed by Daedalus for King Minos of Crete, on a silver tetradrachma from Cnossos, Crete, c. 350–300 b.c. (35 mm, Cabinet des Médailles, Bibliothèque Nationale, Paris). “Such was the work, so intricate the place, / That scarce the workman all its turns cou’d trace; / And Daedalus was puzzled how to ½nd / The secret ways of what himself design’d.”–Ovid, Metamorphoses, Book 8 Dædalus was founded in 1955 and established as a quarterly in 1958. The journal’s namesake was renowned in ancient Greece as an inventor, scien- tist, and unriddler of riddles. Its emblem, a maze seen from above, symbol- izes the aspiration of its founders to “lift each of us above his cell in the lab- yrinth of learning in order that he may see the entire structure as if from above, where each separate part loses its comfortable separateness.” The American Academy of Arts & Sciences, like its journal, brings togeth- er distinguished individuals from every ½eld of human endeavor. It was char- tered in 1780 as a forum “to cultivate every art and science which may tend to advance the interest, honour, dignity, and happiness of a free, independent, and virtuous people.” Now in its third century, the Academy, with its nearly ½ve thousand elected members, continues to provide intellectual leadership to meet the critical challenges facing our world. Dædalus Winter 2015 Subscription rates: Electronic only for non- Issued as Volume 144, Number 1 member individuals–$47; institutions–$129. © 2015 by the American Academy Canadians add 5% gst. Print and electronic for of Arts & Sciences nonmember individuals–$52; institutions– Brain Mechanisms for Active Vision $144. Canadians add 5% gst. Outside the United by Robert H. Wurtz States and Canada add $23 for postage and han- U.S. Government Document: dling. Prices subject to change without notice. No rights reserved Institutional subscriptions are on a volume- Remembering year basis. All other subscriptions begin with by Larry R. Squire & John T. Wixted the next available issue. U.S. Government Document: Single issues: $14 for individuals; $36 for insti- No rights reserved tutions. Outside the United States and Canada Editorial of½ces: Dædalus, American Academy of add $6 per issue for postage and handling. Arts & Sciences, 136 Irving Street, Cambridge ma Prices subject to change without notice. 02138. Phone: 617 576 5085. Fax: 617 576 5088. Claims for missing issues will be honored free Email: [email protected]. of charge if made within three months of the Library of Congress Catalog No. 12-30299. publication date of the issue. Claims may be submitted to [email protected]. Members of Dædalus publishes by invitation only and as- the American Academy please direct all ques- sumes no responsibility for unsolicited manu- tions and claims to [email protected]. scripts. 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An electronic full-text version duce content from Dædalus, please complete the of Dædalus is available from The mit Press. online request form at http://www.mitpress Subscription and address changes should be ad - journals.org/page/permissionsForm.jsp, or con- dressed to mit Press Journals Customer Service, tact the Permissions Manager at mit Press Jour- One Rogers Street, Cambridge ma 02142-1209. nals, One Rogers Street, Cambridge ma 02142- Phone: 617 253 2889; U.S./Canada 800 207 8354. 1209. Fax: 617 253 1709. Email: journals-rights@ Fax: 617 577 1545. Email: [email protected]. mit.edu. Printed in the United States of America by Corporations and academic institutions with Cadmus Professional Communications, Science valid photocopying and/or digital licenses with Press Division, 300 West Chestnut Street, the Copyright Clearance Center (ccc) may Ephrata pa 17522. reproduce content from Dædalus under the terms of their license. Please go to www Newsstand distribution by Ingram Periodicals .copyright.com; ccc, 222 Rosewood Drive, Inc., 18 Ingram Blvd., La Vergne tn 37086. Danvers ma 01923. Postmaster: Send address changes to Dædalus, The typeface is Cycles, designed by Sumner One Rogers Street, Cambridge ma 02142-1209. Stone at the Stone Type Foundry of Guinda ca. Periodicals postage paid at Boston ma and at Each size of Cycles has been sep arately designed additional mailing of½ces. in the tradition of metal types. Neuroscience: The Study of the Nervous System & Its Functions Fred H. Gage Any man could, if he were so inclined, be the sculptor of his own brain. –Santiago Ramón y Cajal, Advice for a Young Investigator (1897) Neuroscience is the scienti½c study of the nervous system (the brain, spinal cord, and peripheral nerv- ous system) and its functions. The belief that the brain is the organ that controls behavior has an - cient roots, dating to early civilizations that con- nected loss of function to damage to parts of the brain and spinal cord. But the modern era of neuro- science began–and continues to progress–with the development of tools, techniques, and methods used to measure in ever more detail and complexity the structure and function of the nervous system. The modern era of neuroscience can be traced to the 1890s, when the Spanish pathologist Santiago Ramón y Cajal used a method developed by the Italian physician Camillo Golgi to stain nerve tis- sues to visualize the morphology and structure of the neurons and their connections. The detailed de - FRED H. GAGE, a Fellow of the scription of the neurons and their connections by Amer ican Academy since 2005, is Cajal, his students, and their followers led to the Professor in the Laboratory of Ge - “neuron doctrine,” which proposed that the neuron netics and the Vi and John Adler is the functional unit of the nervous system. Chair for Research on Age-Related We now know that the human brain contains ap - Neurodegenerative Disease at the Salk Institute for Biological Stud- proximately one hundred billion neurons and that ies. He studies the unanticipated these neurons have some one hundred trillion con- plas ticity and complexity repre- nections, forming functional and de½nable circuits. sented in the brain. These neural circuits can be organized into larger © 2015 by the American Academy of Arts & Sciences doi:10.1162/DAED_e_00313 5 The Study networks and anatomical structures that resent the de½ning features of the neu- of the integrate information across and between ron.