Cognitive Neuroscience

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PS64CH01-Gazzaniga ARI 15 November 2012 12:44

Shifting Gears: Seeking New Approaches for Mind/Brain Mechanisms Michael S. Gazzaniga The Sage Center, University of California, Santa Barbara, California 93106-9660; email: m.gazzaniga@psych.ucsb.edu

Annu. Rev. Psychol. 2013. 64:1–20

First published online as a Review in Advance on September 17, 2012

The Annual Review of Psychology is online at psych.annualreviews.org

This article’s doi: 10.1146/annurev-psych-113011-143817

Copyright c© 2013 by Annual Reviews. All rights reserved

Keywords

split brain, corpus callosum, modular, self-cueing, eye-hand coordination, emotion, dynamical systems

Abstract

Using an autobiographical approach, I review several animal and hu- man split-brain studies that have led me to change my long-term view on how best to understand mind/brain interactions. Overall, the view is consistent with the idea that complex neural systems, like other com- plex information processing systems, are highly modular. At the same time, how the modules come to interact and produce unitary goals is unknown. Here, I review the importance of self-cueing in that process of producing unitary goals from disparate functions. The role of self- cueing is demonstrably evident in the human neurologic patient and especially in patients with hemispheric disconnection. When viewed in the context of modularity, it may provide insights into how a highly parallel and distributed brain locally coordinates its activities to pro- duce an apparent unitary output. Capturing and understanding how this is achieved will require shifting gears away from standard linear models and adopting a more dynamical systems view of brain function.

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PS64CH01-Gazzaniga ARI 15 November 2012 12:44

Contents

INTRODUCTION . . . . . . . . . . . . . . . . . . 2 THE EARLY YEARS . . . . . . . . . . . . . . . . 3 THE CALTECH YEARS WITH

ROGER SPERRY . . . . . . . . . . . . . . . . . 4 UNCOVERING BRAIN

MECHANISMS: THE ROLE OF SELF-CUEING . . . . . . . . . . . . . . . 5

COGNITIVE AND EMOTIONAL CUEING . . . . . . . . . 9

THE INTERMEDIATE YEARS . . . . . 11 THE INTERPRETER . . . . . . . . . . . . . . . 13 THE GIFFORD LECTURES

AND MOVING FORWARD . . . . . . 14 INTERACTING MODULES:

THE VAST UNCONSCIOUS . . . . 17 A FINAL WORD . . . . . . . . . . . . . . . . . . . . 18

INTRODUCTION

With all we know about memory and its fail- ings, any kind of retrospective should be sus- pect. How many times have we called up past experiences that seem key to our lives, rolled them around, and then let current times tag them before putting them back to sleep? Over time, how can our memories possibly resemble the way things truly were?

There is something about the personalities we have known, however, that sticks and seems as true to us in the present as it was the day we formed our opinion about the stuff of certain people. Class reunions are a telling moment. Harry, 50 years later, is still an ass, while Bob is still cool. Even though we have not laid eyes on them since graduation night, the 50 intervening years have done nothing to change our views. On the other hand, and somewhat paradoxi- cally, our ideas on how to understand mech- anisms of nature do seem to change. These stubborn realities are fair warning about what follows. In short, my views on the flow of events and ideas that have captured my interests are undoubtedly influenced by all these intangibles.

When I began my intellectual journey of the past 50 years or so, the world and its challenges were to be understood in straightforward ways, with simple models of structure/function rela- tionships being the dominant reality. In animal research, make a lesion, see what happens. Make another lesion, see what happens. In hu- man research, study all patients who happen to have lesions in different places or study surgical patients who have particular kinds of disconnec- tions. Or, in both animal and human physiol- ogy, eavesdrop on neurons and see if the neural code that directs behavior can be figured out.

The straightforward thrusts of youth in a scientific field that was itself young are telling and important. Yet what is more important to realize is that scientific progress, as it unfolds in spurts of insight arriving in a field of hard, mun- dane work, is commonly disorderly and mostly nonlinear. Stuff happens along the way. One influences others and at the same time is mas- sively influenced by others. One of the beautiful things about science is that how one looks at a body of work after it is completed might well pose questions that are different from those that one originally imagined. While this shifting perspective is going on, the experiments con- ducted sit there, unmistakable and sure-footed. Their ultimate richness, or possible banality, fluctuates as surrounding knowledge and the- ory accrue to our human culture.

In my case, one overarching truth, which emerges from split-brain research as well as the study of neurological disorders and functional imaging studies, is that the human brain is not an all-purpose centralized computing device. Instead, it is organized in modular fashion, consisting of distributed, specialized circuits that have been sculpted by evolution and development to perform specific subfunctions while somehow preserving substantial plasticity (Gazzaniga 2011).

In the past, when experimental results were consistent with this perspective, it was enough to stop there. Clearly, however, such a formula- tion begs the question: How does a distributed mechanical process give rise to unitary, func- tional output? Over the years, many experiences

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PS64CH01-Gazzaniga ARI 15 November 2012 12:44

and new hunches have made me realize that if any deeper understanding of mind-brain rela- tionships is to come about, it would necessitate shifting to a more dynamical systems approach. My animal work, my work on patients, and my endless discussions with students, friends, and colleagues led me to this conclusion. My goal in this essay is to capture this journey of discovery and to illuminate how this view came to be.

THE EARLY YEARS

For me, it all started with a feeling—a feeling about the need to know “What’s it all about?” I can trace it back to my teenage years and often thought it was promoted by being the fourth out of five children of Dante and Alice Gazzaniga. For many years, I was the youngest and was less differentiated than my older brothers and sis- ter. It fell to me to keep the peace in a vigorous family. When my younger sister came along, my role changed as my older siblings shipped out to college and I was left behind to help raise Becky with my parents. Everybody loved Becky, so it was more like the three of us were competing to take care of her.

This is all to say that there are always plenty of social forces around us shaping and modify- ing our natural dispositions. My disposition was “contrarian.” If somebody said this is the way things are, I was always thinking about the al- ternatives. In part, this also relates to my many inadequacies at advanced quantification, so I always tried to frame whatever issue was being discussed in more accessible terms. Sometimes it worked wonderfully; sometimes it was a total bust. So, quantitative skills do not come nat- urally to me. To the extent that I possess any, they were hard to acquire and were never “felt.” When I was a graduate student at Caltech, and for some reason or another I had to learn how to derive the laws of thermodynamics, I did it totally by rote and got through it. After I was done, I can remember complaining to Seymour Benzer that I simply didn’t get it, didn’t feel the laws. Benzer said, “That’s all right, most physicists don’t either.” Benzer was a very gentle man.

This is all presented in the spirit of full disclosure. I am not quantitative, period. And yet for 50 years I have enjoyed a rich intellec- tual life with scientists who are exceptionally gifted in mathematics. What’s up with that? I once heard Duncan Luce say that statistics should not be taught to psychologists. He felt the newly trained students would come to think that statistics was the important part, not the question being examined. Often we hear spe- cialists talk endlessly about the quantitative de- tails of their research, whereas they are seem- ingly blasé about the net idea that comes out of all the work. This is the danger Luce was talk- ing about, and I think we all see this happening far too frequently.

More fundamentally, the feeling of being in- terested in the question of what life is all about is a wonderful center for the mind. Whatever crazy, mindless activity one might be engaged in during the day, whether it be learning his- torical facts, a foreign language, or how to play football, coming home mentally each night to that question has been a wonderful tonic. One’s mind really is an exclusive island that one can retreat to frequently, if not daily, where no one can bug you, and where one’s own interpreta- tions of the world are continually revised and updated.

Somehow all of this was working on me early in life and found me trotting off to Dartmouth College, where my older brilliant brother Alan was already a star football player and a man about town, soon to enter medical school. His tales of life in Hanover captivated me, and I dearly hoped I would get in. It all worked out, and from the moment I hit the Hanover plain I was in love with it all. The freshman beanie was placed on my head, and for a week I schlepped furniture up and down dorm steps for the upperclassmen. Somehow, it was exciting and refreshing.

Then I discovered Baker Library with its fa- mous Tower Room. One could grab a book, sit in a carrel, and read away the afternoon. I discovered Crime and Punishment there and be- came mesmerized by my new life. To this day, I think of that experience with a fondness that

www.annualreviews.org • Mind/Brain Mechanisms 3

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