This editorial introduces a special issue on brain asymmetry in development, psychopathology, and evolution. It summarizes several of the articles in the issue. The issue explores how brain asymmetry is related to cognition, emerges in evolution, develops over a person's lifetime, and relates to individual differences and psychopathology. It finds that some forms of brain asymmetry are ancient and shared across species, while others are unique to humans. The issue investigates theories on the emergence of brain asymmetry and its implications.

1. Cogniţie, Creier, Comportament / Cognition, Brain, Behavior
Copyright © 2006 Romanian Association for Cognitive Science. All rights reserved.
ISSN: 1224-8398
Volume X, No. 2 (June), 159-161
EDITORIAL: BRAIN ASYMMETRY IN
DEVELOPMENT, PSYCHOPATHOLOGY AND
EVOLUTION
Joseph B. HELLIGE *
University of Southern California, Los Angeles, CA, USA
I was delighted to receive an invitation from Andrei Miu to prepare an
article for this special issue of Cognition, Brain, Behavior, for which my long-time
USC colleague, Joe Bogen was serving as Guest Editor. Given Joe’s seminal
contributions to study of the split-brain patients (see Eran Zaidel’s article in this
issue), it seemed especially fitting that the theme of the special issue would be
brain asymmetry in psychopathology, development and evolution. Having readily
accepted the invitation, I had just begun to work on my contribution when we
learned of Joe’s passing. When Andrei asked if I would step in as a co-Guest
Editor, I agreed to help in whatever way I could to see this timely project through
to completion. As you can see, the result is a set of provocative articles by an
international cast of fine scholars.
We have known for a long time that the left and right sides of the cerebral
cortex are functionally asymmetric in humans. Nothing has done more to illustrate
the profound nature of that asymmetry than the pioneering study of split-brain
patients by Roger Sperry, Joe Bogen and their colleagues, work for which Sperry
received the Nobel Prize in 1982. The value of understanding the brain’s functional
asymmetry, or laterality, goes far beyond an attempt to localize perceptual,
cognitive and emotional processes in the brain. Indeed, with respect to localization
it is now possible to be far more precise than to simply indicate whether one
hemisphere is superior to the other. Instead, the brain’s laterality constitutes an
emergent organizational property that is no less important to understand today than
it was 50 years ago when Bogen and Sperry first met. During the intervening years,
much has been learned about the nature of laterality, the manner in which it may
have emerged during the course of evolution, the manner in which it develops over
the life span of an individual and how individual differences in lateralization may
*
Corresponding author: Dr. Joseph B. Hellige, Department of Psychology, SGM 502,
University of Southern California, Los Angeles, California 90089-1061, USA.
E-mail: hellige@usc.edu.

2. 160 J. B. Hellige / Cognition, Brain, Behavior 10 (2006) 159-161
be related to individual differences in cognitive abilities, propensities and
pathology. The articles in this special issue provide a snapshot of what we have
learned so far and, of even more importance, a glimpse of what the future holds.
It seems fitting to begin by reprinting one of Bogen’s last articles,
discussing Sperry’s philosophy of mind. As always, Bogen did not shy away from
the truly big issues, in this case the emergence of consciousness and the
relationship between mind and brain. Though prepared as an exposition on
Sperry’s views, Bogen’s article inevitably articulates his own view of the manner
in which mind arises from brain. It is noteworthy that the ideas articulated in that
article remain timely. Something of both Bogen’s views and personality are nicely
captured in one of his footnotes:
When I argued this [a particular view of the mind-brain relationship] with
Paul Churchland he exclaimed ‘Throughout the history of this subject
[certainly since Descartes] the mind has been considered to be between
God and brain. But now you presume to put the brain between God and
mind.’ Exactly so, which is how I can be a committed physicalist while
remaining agnostic (or even indifferent) about the immaterial.
When Bogen and Sperry began working together, laterality was thought to
be either uniquely human or so qualitatively different in humans that the few cases
where it existed in other contemporary species were unlikely to shed light on how
it emerged in our own species. That view has changed dramatically, especially
within the last 20 years. The article by Vallortigara and Regolin reviews the
ubiquity of brain lateralization in non-human animals. They note striking
similarities between laterality in humans and other species, similarities that may
have profound implications for both ontogeny and phylogeny. The fact that some
forms of laterality are ubiquitous across species and, thus, likely to be quite old in
evolutionary terms suggests that there are computational advantages of separating
complementary processes into two sides of the brain, an idea explored in my own
article (Hellige, this issue). Of course, human laterality differs in important ways
from that of even our own closest primate relatives, leading to consideration of the
manner in which several important milestones in human evolution shaped laterality
into the pattern characteristic of contemporary humans.
A particularly influential theory regarding the emergence of laterality both
ontogenetically and phylogenetically has been the right shift theory first proposed
by Marian Annett nearly 30 years ago. In her article in this issue, Annett reviews
the right shift theory, arguing that the RS+ gene [which induces an advantage for
the left hemisphere by weakening the right hemisphere] is specific to humans,
creating something of an evolutionary discontinuity with other species. Her article
also considers the role of the RS+ gene and various mutations of that gene for
development and psychopathology.

3. J. B. Hellige / Cognition, Brain, Behavior 10 (2006) 159-161 161
The article by Simic, Mladinov, Juda and Hof reviews anatomical brain
asymmetries related to language with emphasis on entorhinal cortex and basel
forebrain. As they demonstrate, anatomical asymmetries can be used to shed light
on the evolutionary foundations of laterality and language, on the possible
similarity across species and on correlates of disturbed development of
hemispheric asymmetry and asymmetric brain damage.
The article by Papousek and Schulter notes how contemporary
neuropsychological models of affect and affective disorders have served to revive
interest in functional hemispheric asymmetry. They discuss a variety of issues that
must be considered in the investigation of hemispheric asymmetry for emotion and
for studies that relate individual differences in laterality to psychopathology. The
article by Lohr, Caligiuri, Sponheim, Dean and Cortese reviews evidence for
lateralized abnormalities in schizophrenia, especially abnormalities in the left
hemisphere. More specifically, they present new analyses to show that, relative to a
control group, schizophrenic patients and their first-degree family members have
difficulty maintaining a steady-state force with their right hand (left hemisphere),
possibly related to asymmetrical functioning of the basal ganglia. The article by
Fritzsche, Fritzsche, Kosidubova, Prognimak and Mayorov also discusses the
relationship between brain asymmetry and schizophrenia, as well as implications
for the development and evolution of functional brain asymmetry. In particular,
they consider how asymmetric stimulation of left and right visual fields might
serve to introduce hemispheric differences for processing aspects of visual stimuli,
how a novel task may switch from right- to left-hemisphere dominance with
practice and how a mathematical measure derived from information theory
(Kolmogorov entropy) can be used to study these phenomena as well as
relationships between laterality and psychopathology.
As the title of this journal implies, cognition, brain and behavior are
intertwined. The goal of cognitive neuroscience is to unravel the relationships so as
to understand how our cognitions and behaviors arise from brain. As Bogen’s
article indicates, there is also a sense in which emergent properties like what he
and Sperry term “mentation” may, in turn, influence elements of neural activity.
The articles in this special issue remind us that left/right brain asymmetry
constitutes an important emergent property that we share to some extent with other
species and that is related to our cognitive development and to psychopathology.
As such, understanding hemispheric asymmetry and the manner in which the two
hemispheres interact to produce unified performance will continue to be an
important component in understanding the relationships among cognition, brain
and behavior.