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.