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:
All Adv. classes require successful completion of the 4 Day Comprehensive Beta/SMR.
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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 |
It is always difficult to estimate odds from a single occurrence. The New England Patriots won their first championship this year, after 42 years of existence. Does this mean that they have a 1 in 42 chance of repeating next year? Or a 1 in 32 chance, given the number of teams in play next year? Or 1 in 1 chance of repeating as champs? Yeah, that's likely....
The search for extraterrestrial intelligence (SETI) often focuses on the odds of finding a signal from an alien civilization. In 1961 Frank Drake created a general formula to determine the probability of intelligence in our galaxy. Essentially the formula estimates the probability of Earth-like planet orbiting around suitable stars multipled by the probability of life appearing on such a planet multiplied by the probability of life advancing all the way to intelligence multiplied by the chance of being available for communication at the time of our search.
Carl Sagan worked with Drake and he estimated that because the galaxy contains 400 billion stars and possibly 100 billion galaxies, the probability of intelligent life beyond Earth was virtually certain and in fact the universe might be densely populated with alien civilizations.
But another renown scientist Enrico Fermi asked in 1950, if extraterrestrials are commonplace, then "where are they?" Given the presumed headstart of a billion or even a few million years (our solar system was born late, 8-10 billion years after the Big Bang), most space-faring civilizations could have colonized the entire galaxy or local Supercluster by now. That we are not exhibits in a celestrial zoo (or so we think!), we can presume that either our real estate is located in a galactic backwater, or we have luckily remain undetected by alien colonizers.
But these speculations were formed before recent evidence and models were available. With this new evidence, and applying Drake's equation to our own habitat, we can ask with some modest degree of confidence how unusual, how rare, this planet is.
Drake's formula asks for the probability of suitable stars and earth-like planets around those stars. We actually have firm data on extrasolar planet formation. No earth-size planets yet detected, given our techniques, but of 1,000 nearby stars, 10% have planets. Interestingly, most of these systems exhibit weird formations (Jupiter-sized planets in Mercury-size orbits around the star), high metallicity, and/or elliptical orbits, which are unfriendly to terrestrial planets.
Next his formula asks for the probability of life. Simple life such as microbes may be ubiquitous throughout the stars. Water plus chemicals plus time may equal life. Life on our own planet emerged as soon as possible, as soon as the Earth cooled enough to support it, which suggests it was a modest step from available carbon to carbon-based reproduction. Yet, on the other hand, there is evidence against life as a simple step. Life developed only once on this planet, at one site, presumably. We have only one DNA strand present on the planet, from ameoba to algae to Albert Einstein. If organic chemistry is a small step from inorganic chemistry, wouldn't other DNA variants exist?
Unicellular life can withstand high pressure, high and cold temperatures (from 0 to 167 degrees Celsius). Multicellular life is not so flexible. It requires stable pressures, small temperature ranges (0 to 50 degrees Celsius), and it takes an unknown and unique process that moves uni- to multicellular life. Single cell creatures appeared about 3.8 billion years ago, but for 3.3 billion more years, multicellular life was but a dream. What caused such anti-symbiotic inertia is beyond me? it's been 550 million years or so since this transition to the human brain. That's an awfully long time to keep a planet's climate stable, and relatively free of catastrophic bombardments.
A stable environment (where water remains in liquid form) for a billion years or so requires an amazing degree of balance and luck. Habitable zones require an improbable mixture of mass, composition, position, and timing. We live in a Goldilock's world: not too hot (not to close to the parent star), not too cold (not to distant). Let me quickly run through the variables.
In the space left I cannot explain the estimated odds for every feature above. Suffice it to say that many of the situations are uncommon. For instance, plate tectonics appears to be a critical need for intelligent life to evolve and of 83 or so planetary bodies in our solar system, Earth is the only one with plate tectonics. That we live in the corotational plane of our galaxy, away from the vibrant and deadly arms where stars are born and die (with radiation-spewing bangs), appears to be a necessity. If not, every 10 million years we'd either pass by a nemesis star and pull a terrestrial planet or two out of orbit or a supernova would explode nearby, eliminating all creatures vulnerable to gamma radiation (i.e., all).
The most improbable element of our planet's formation must be our satellite. Without the moon, we would wobble on our axis as much as Mars, which moves from 0 degrees to 90 degrees every 10 million years or so. Imagine a spider monkey species having to adapt to the Sahara and then a few million years later, the Antarctic. The Moon reduces our wobble to a mere 2 1/2 degrees, very tolerable. But how did we obtain such a large satellite? According to the Apollo Moon missions, the Moon and Earth are the spherical fragments of two proto-sized planets striking each other at the right time at the right place and at the exactly right angle. Normally such collisions would leave a debris field, quickly reabsorbed by the larger planetary mass (like Saturn's rings) or many small satellites. Without our large moon, tidal pools would not exist, and probably multicellular life would have remained a dream. So, what are the chances of another terrestial planet possessing such a large satellite? Astronomical. Essentially zero. Say, somewhere between a 1 in a billion and 1 in 400 billion billion (which would make our planetary system Earth-Moon unique in the cosmos).
So what are the odds of a more complex brain existing on a distant planet?
Probably less than we'd care to imagine.