Brain Hemispheres

See also:    Neuropsychology   

Internet Resources

We report a whole-brain MRI morphometric survey of asymmetry in children with high-functioning autism and with developmental language disorder (DLD). Autism and DLD were much more similar to each other in patterns of asymmetry throughout the cerebral cortex than either was to controls; this similarity suggests systematic and related alterations rather than random neural systems alterations. We review these findings in relation to previously reported volumetric features in these two samples of brains, including increased total brain and white matter volumes and lack of increase in the size of the corpus callosum. Larger brain volume has previously been associated with increased lateralization. The sizeable right-asymmetry increase reported here may be a consequence of early abnormal brain growth trajectories in these disorders, while higher-order association areas may be most vulnerable to connectivity abnormalities associated with white matter increases.
M.R. Herbert et al
This article provides a review of research on the hemispheric specialization in emotional processing during the past 40 years and the theoretical models derived from the conceptual analysis of these results. The publications reviewed here were collected to better appreciate the cortical lateralization of emotional perception (visual and auditory), expression (facial and prosodic), and experience. Four major models of emotional processing are discussed—the Right Hemisphere, Valence, Approach-Withdrawal, and Behavioral Inhibition System–Behavioral Activation System models. Observing the relative merits and limitations of these models, a new direction for exploration is offered. Specifically, to better appreciate the strength and direction (i.e., approach versus withdrawal) of experienced emotions, it is recommended that state "dominance" be evaluated in the context of asymmetrical activation of left-frontal (dominance) versus right-frontal (submission) brain regions.
Heath A. Demaree et al
Though we may prefer the use of certain quadrants of the brain, they have evolved to work together for full human functioning, as the non-dominant hand is needed to work with the dominant hand.
Donna Stevenson
The surgical disconnection of the cerebral hemispheres creates an extraordinary opportunity to study basic neurological mechanisms: the organization of the sensory and motors systems, the cortical representation of the perceptual and cognitive processes, the lateralization of function, and, perhaps most importantly, how the divided brain yields clues to the nature of conscious experience. Studies of split-brain patients over the last 40 years have resulted in numerous insights into the processes of perception, attention, memory, language and reasoning abilities. When the constellation of findings is considered as a whole, one sees the cortical arena as a patchwork of specialized processes. When this is considered in the light of new studies on the lateralization of functions, it becomes reasonable to suppose that the corpus callosum has enabled the development of the many specialized systems by allowing the reworking of existing cortical areas while preserving existing functions. Thus, while language emerged in the left hemisphere at the cost of pre-existing perceptual systems, the critical features of the bilaterally present perceptual system were spared in the opposite half-brain. By having the callosum serve as the great communication link between redundant systems, a pre-existing system could be jettisoned as new functions developed in one hemisphere, while the other hemisphere could continue to perform the previous functions for both half-brains. Split-brain studies have also revealed the complex mosaic of mental processes that participate in human cognition. And yet, even though each cerebral hemisphere has its own set of capacities, with the left hemisphere specialized for language and speech and major problem-solving capacities and the right hemisphere specialized for tasks such as facial recognition and attentional monitoring, we all have the subjective experience of feeling totally integrated. Indeed, even though many of these functions have an automatic quality to them and are carried out by the brain prior to our conscious awareness of them, our subjective belief and feeling is that we are in charge of our actions. These phenomena appear to be related to our left hemisphere's interpreter, a device that allows us to construct theories about the relationship between perceived events, actions and feelings.
Michael Gazzaniga
Cell adhesion molecule proteins play a diverse role in neural development, signal transduction, structural linkages to extracellular and intracellular proteins, synaptic stabilization, neurogenesis, and learning.
Marquis Vawter
You are constructed in a cross-linked fashion: your left eye is connected to your right brain hemisphere and vice-versa. This means that the left eye indicates your right-hemisphere activity and your right-eye indicates your left-brain activity.
Fergus Reilly
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Middle Tennessee State University Developmental Studies Department
Results support the hypotheses that right hemisphere dysfunction is implicated in developmental semantic-pragmatic language disorder and in high-level autism, and that semantic-pragmatic language disorder forms part of the autistic continuum.
Jane Shields
People show a left visual field (LVF) bias for faces, i.e., involving the right hemisphere of the brain. Lesion and neuroimaging studies confirm the importance of the right-hemisphere and suggest separable neural pathways for processing facial identity vs. emotions. We investigated the hemispheric processing of faces in adults with and without Asperger syndrome (AS) using facial emotion and identity chimeric tasks. Controls showed an LVF bias in both tasks, but no perceptual bias in a non-social control task. The AS group showed an LVF bias during both tasks, however the bias was reduced in the identity condition. Further, the AS group showed an LVF bias in the non-social condition. These results show a differential pattern of hemispheric processing of faces in AS.
C. Ashwin, S. Wheelwright, S. Baron-Cohen
The mode of processing used by the right brain is rapid, complex, whole-pattern, spatial, and perceptual, processing that is not only different from but comparable in complexity to the left brain's verbal, analytic mode.
Betty Edwards
Attractive image of the brain and its hemispheres.
Three Point Productions
The development of functional brain asymmetry during childhood is confirmed by changes in cerebral blood flow measured at rest using dynamic single photon emission computed tomography. Between 1 and 3 years of age, the blood flow shows a right hemispheric predominance, mainly due to the activity in the posterior associative area. Asymmetry shifts to the left after 3 years. The subsequent time course of changes appear to follow the emergence of functions localized initially on the right, but later on the left hemisphere (i.e. visuospatial and later language abilities). These findings support the hypothesis that, in man, the right hemisphere develops its functions earlier than the left.
C. Chiron et al
The need for a diagnostic nosology and improved and validated intervention techniques is stressed as is early identification of these types of specific nonverbal learning disabilities.
Margaret Semrud-Clikeman
The communication difficulties displayed by both some patients with acquired right hemisphere lesions and children with semantic-pragmatic language disorder indicate a failure to understand the processes of inference.
Jane Shields
Explores the function of the brain's hemispheres, how information is shared between them via the largest of the interhemispheric commissures, and what symptoms result as a consequence of a split brain operation in which the commissure is severed.
A. Senders

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