A Monthly Summary of News and Events
Vol. 5 No. 3 - March 2002
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The rise of civilization is a story of increasing dominance of analytical, symbolic thought over more primitive modes of representation. Today's left brain dominance is especially interesting because it does not appear to be our natural state. Individuals raised outside of industrial societies, in aborginal cultures in North America or Australia, or socially isolated children, tend to develop right-brain dominance. For example, Genie, a terrible case of neglect and social isolation, did not acquire any language until adolescence (Curtiss, 1986) and she exhibits right brain dominance for most mental processes including her limited language skills -- this, in spite of strong right handedness. Cultural hemisphericity was investigated by Bogen and TenHouten 30 years ago, and although controversial, individuals raised in urban settings were generally found to possess greater analytical and poorer visuospatial abilities compared to peers raised in rural settings, including Native Americans. Historical evidence also suggests that our left brain dominance is recent, a few thousand years old at best (Jaynes, 1976). Early writing systems predate the transition to left-brain dominance and most adopted a right-to-left writing direction (e.g., Phoenician, Hebrew, pre-Ionian Greek), a convention that places the ends of words, where disambiguation occurs, into the left visual field/right hemisphere. This would be expected for a right-brain dominant reader.
Global brain function may be characterized as two modes of ideation in competition. We start out life with probably something closer to no cerebral dominance or slight right-brain dominance but our modern-day cultures develop, or overdevelop, our left-brain faculties. Cerebral dominance, left brain dominance, is learned. Like any skill, it may be acquired well, poorly, or not at all. And it may be lost or reduced with injury or prolonged stress.
Task hemisphericity, performing a task within a single hemisphere, is the foundation of behavioral neurology and cognitive neuroscience (Broca, 1861). Facial recognition, for instance, is performed in your right hemisphere (RH). Speech and metaphor, calculation and visualization, perception of phonemes and perception of emotions, all of these tasks are strongly lateralized. Left hemisphere structures mediate positive emotions such as mania and right brain mechanisms underlie most negative emotions (Davidson, 1998; Robinson & Downhill, 1998). Occasionally the two modes of processing are complementary, supplementary, but often the hemispheres act like feuding youngsters, ignoring the other, interfering with each other. In split brain patient research, it is not uncommon to obtain a response from a hemisphere poorly equipped for a task, even when the other hemisphere is an expert for such stimuli. The same is true for normal, intact individuals (e.g., Zaidel, 1998). So competition may be the rule inside the head as well out.
Most of us rely on verbal communication and logical thinking to proceed through life and society. But the verbal, analytical dominance is learned, not intrinsic to our bicameral neural architecture. In fact right brain dominance may be our pre-linguistic state. In response to severe environmental and personal stressors, some may regress back to this balance, often with drastic behavioral consequences. Failure to lateralized critical language functions during development, both anatomically and functionally, may be the cause of schizophrenia (Crow, 1997; 2000). Leonhard and Brugger (1998) proposed that dominance failure, prominent during acute psychosis, underlies the emergence of paranormal and delusional beliefs. The right hemisphere's semantic network is coarse, less tightly focused around conventional meanings than the left's. When dominance shifts away from the left, unfocused, nonconventional thoughts and beliefs may predominate an individual's mentation. Such a mode of processing may spark creativity or it may lead to disturbed (clinically so) behaviors.
Perhap worse than dominance failure is what I call "superdominance" -- extreme cerebral dominance. Hemispheric dominance must be tempered by robust function of the other hemisphere. If the nondominant mode of ideation is underdeveloped and excluded from contributing significantly to behavior, clinical syndromes may arise. Paranoia may reflect an unrestrained left brain dominance. A better example is Asperger's syndrome, which shares many clinical features with acquired right-hemisphere dysfunction and may be a developmental abnormality of the right hemisphere. Autism itself sometimes indicates superdominance (poor social communication and empathy) and sometimes dominance failure (poor language development). Savant skills, observed in one-tenth of all autistic individuals, may be an extreme example of superdominance.
The hemisphere competition model has obvious implications to neurotherapy. Neurofeedback can be a powerful method for balancing hemispheric processing, integrating the two sides of the brain. It may be one of the few techniques that can redress dominance failure or superdominance without serious side effects. Merely periodically activating one hemisphere more than the other may be all that is needed to re-establish dominance or allocate attention to underused faculties. Unihemispheric activation may be therapeutic for certain clinical populations.
In 1970 Eran Zaidel developed the z-lens, contact lenses that darkened half of the visual field, either the left or right sides. His research focused on split-brain patients and hemispheric specialization, and he did not investigate clinical applications of this device, but now others have. Schiffer (1997) placed masking tape over the left (LVF) or right visual fields (RVF) of safety glasses and he found that 42 of 70 patients reported more anxiety while wearing his glasses. Depressed patients reported more anxiety with LVF glasses (RVF-blocked/RH activating) and PTSD patients had more anxiety waering RVF glasses. Unihemispheric activation may also improve attention and functioning in other patient populations (e.g., autism, Portia Iverson, pers. communication). Unihemispheric activation should also be readily attained with photic stimulation by simply instructing the individual to look far to the right or far to the left (even with eyes closed), thereby restricting stimulation (primarily) to one visual field, one hemisphere. Neurofeedback training might also be enhanced for some populations by wearing z-glasses during part of a session.
To increase unihemispheric activation, auditory stimulation should be reduced by plugging the contralateral ear. Unlike vision, our auditory system is not perfectly crossed, but the ipsilateral (same side) pathway is weaker so plugging the contralateral ear should diminish auditory contributions to the opposite hemisphere. So to activate the left hemisphere, block the LVF and plug the left ear. Given different widths between eyes, glasses may need to be adjusted for each individual. One easy way to adjust them is to look straight into a mirror and align the tape until half the pupil cannot be seen by the wearer.
Who knows? The simplest methods sometimes yield surprising and powerful results.
Of course, which hemisphere to activate (or deactivate) remains a question. Nearly all right-handed males (99%) represent language in the left hemisphere and non-verbal, visuospatial, and emotional functions in the right hemisphere (especially if they have no familial history of left-handedness), but left handers and women are often less lateralized, though most follow the same trend. One quick-and-dirty method to identify hemispheric specialization without a Wada test is to ask which face below is happier. If the individual chooses the left face (frown in LVF, smile in RVF), emotional processing is presumed to be located in the left hemisphere, and thus language in the RH. The more common response is to choose the right face, with a smile in the LVF. Good luck. Identifying functional asymmetries is a messy business.
Related reading
News & Reviews
NEW BOOKS
Stimulant Drugs and ADHD: Basic and Clinical Neuroscience
by Mary Solanto, Amy Arnsten, F.Castellanos
Brain Injury
Understanding Other Minds: Perspectives from Developmental Cognitive Neuroscience
Cerebral Palsies: Epidemiology and Causal Pathways
Bipolar Disorders: Basic Mechanisms and Therapeutic Implications
Psychological mechanisms in the transition from acute to chronic pain: over- or underrated?
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Psychological factors are related to the onset of back pain as well as to the development of chronic pain, and displayed more predictive power than biomedical or biomechanical variables.
Posttraumatic stress disorder in children. The influence of developmental factors.
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Childhood PTSD needs to accommodate developmental factors, including knowledge, language development, memory, emotion regulation, and social cognition.
Abnormal Functional Connectivity in Posttraumatic Stress Disorder.
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PTSD was characterized by more activation in inferior parietal lobes and left precentral gyrus than controls, and less activation in inferior medial frontal lobe and right inferior temporal gyrus.
QEEG In Psychotropic Drug Development, Drug Treatment Selection, and Monitoring.
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QEEG can assist physician in confirming clinical diagnoses, selecting psychotropic drugs for treatment, and drug treatment monitoring.
Attention deficit/hyperactivity disorder across the lifespan.
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Reviews the most common neurobehavioral disorder presenting for treatment in youth - ADHD.
Changes in brain function of depressed subjects during treatment with placebo.
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"Effective" placebo treatments induce changes in brain function (albeit in "cordance") that are distinct from those associated with antidepressant medication.
Cingulotomy for treatment-refractory obsessive-compulsive disorder.
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Neurosurgical removal of the cingulate was viewed as a successful treatment for OCD although only 1/3 of patients responded well. Not very convincing given presumable deficits that follow lost of this important structure.
Upcoming Courses
Prerequisites:
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Conferences for Neurofeedback Clinicians & Researchers | ||
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| CONFERENCE | LOCATION | DATES |
| SNR - http://www.aapb.org | Scottsdale, AZ | Sep 12-15 |
Temporal lobe epilepsy (TLE) is often considered the source of mysticism throughout history, and I conceive the symptoms associated with the auras and transfigurations of TLE as right hemisphere dominance. Either one is mystic or delusional, relying on half of the brain's beliefs. As I go about my day teaching students I'd guess that half of the students are mystical and half delusional, with most of the professors falling on the delusional side (all left brained). Recently one of my students explained that she had TLE and I immediately looked for the interictal traits or signs for the disorder:
Stickiness is another term for s_talking, from previous generations. In fact he started s#alking me out at my office, making him a rather lazy stal)ker. The only more lazy one would wait for people to come to her... "I hold office hours twice a week... you are obligated to drop by!
My student wanted to study right hemisphere function in juvenile delinquents, to see whether social and emotional functions were impaired. Given her TLE I expect an interest in religious issues will surface soon, or I may suggest it. Are the religious more right-brained or left-brained? Sacredness may be communication between rarely activated areas of the temporal lobe, those activated with a seizure. We may find out and then, if so, we could use operant conditioning to activate such communication without resorting to seizures.
- David Kaiser