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PS64-FrontMatter ARI 21 November 2012 19:14
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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: [email protected]
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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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