What's New in Neurofeedback

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  All links at: news.yahoo.com/fc/Science/Brain_Research

For more than a hundred years we've known that certain brain functions are performed solely within one hemisphere and not the other (e.g., Broca, 1865; Coslett, 2007). Speech and metaphor, mathematical calculation and visual imagery, perception of phonemes and perception of emotions, are all strongly lateralized. Facial recognition, for instance, is localized to the right posterior hemisphere in most individuals and damage to the left posterior cortex has little effect on this function. Left hemisphere structures alone appear to mediate appetitive drives and positive emotions whereas right brain structures underlie aversive states and negative emotions such as disgust (Davidson, 1998; Robinson & Downhill, 1995). Occasionally the two modes of processing are complementary, but often each hemisphere feud like siblings, interfering with the other’s behavior. 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 better organized to handle such stimuli such as phoneme identification. The same is true for normal (brain intact) individuals (e.g., Zaidel, 1995), which means that competition is the rule inside the head as well as out.

That brain function reflects incompatible modes of ideation in constant competition with each other has powerful implications for neurotherapy. Neurofeedback may be used to restore balance to hemispheric processing and initiate a reintegration of the two sides of the brain, or it may be used to differentiate hemispheric function when that is called for. Periodically activating one hemisphere and not the other can allocate attention to underused faculties and even help establish left-sided dominance when lacking. Unihemispheric activation on its own, regardless of induction technique, may prove to be effective for a wide range of psychopathologies. In 1970 Eran Zaidel developed the z-lens, contact lenses with darkened visual fields, either the left or right half. (Z-lens were recently featured on the CBS show "3 Lbs".) His research focused on split-brain patients and hemispheric specialization, and not clinical application directly, but Schiffer (1997) revived z-lens for therapy. He placed masking tape over the left (LVF) or right visual fields (RVF) of safety glasses and he found that most patients reported more anxiety while wearing the z-glasses (though he did not call the apparatus by this name). Depressed patients reported more anxiety with LVF glasses (RVF-blocked/RH activating) and PTSD patients had more anxiety wearing RVF glasses.

In terms of neurotherapy, preferential activation or inhibition of a single hemisphere may augment the therapeutic effect of EEG training. Unihemispheric activation or inhibition could be readily attained with unilateral (one-sided) photic stimulation by simply instructing individuals to look far to the right or left (even through closed eyelids), thereby restricting stimulation to one visual field and one hemisphere. Or EEG biofeedback could be lateralized by wearing z-glasses during part of a session, or by simply instructing a client to focus to the left or right of the field of stimulation (i.e., left or right edge of the PC monitor). I made my own pair of z-glasses last year and watched a movie in a theatre so adorned. Although my occluded right brain should have been able to "watch the movie" via signals through my intact corpus callosum (minimizing the effect of stimulus lateralization), it didn’t. Wearing the unusual glasses changed the experience (and not just socially!). It made the film’s story hollow, with little emotional traction, until I took the glasses off and let my right brain share in the content stream directly. Apparently the 200-million-fiber "ether cable" between my hemispheres down-sampled the content so that my right brain caught only a rendering of the information and not the information itself. In other words callosal transfer is no substitute for direct input via the senses. So the z-glasses work.

I also wore an ear plug in my left ear while watching the film. Unilateral acoustic stimulation is another way to facilitate unihemispheric activation. Unlike vision, our auditory system is not perfectly crossed and each ear sends information to each hemisphere. Fortunately, in this context, the ipsilateral (same side) pathway is weak so plugging the contralateral ear should greatly diminish auditory contributions to this hemisphere. Dichotic ear presentations using stereo headphones with reward sent into the contralateral ear and white noise or competing sounds in the other would be the optimal approach to leverage the auditory system for unihemispheric activation. So to activate the left hemisphere, one may block the LVF and plug the left ear (or send competing irrelevant sounds to this ear). To activate the right hemisphere, block and plug the right visual field and ear. Given different widths between human eyes, z-glasses should be tailored to the individual (i.e., each client gets her own taped safety goggles). To adjust z-glasses to an individual, the wearer looks straight into a mirror and aligns the tape until only half of his or her pupil of each eye can be seen by the wearer. As for unihemispheric acoustic stimulation, if different sounds cannot be channeled separately into left and right stereo headphones, two sets of headphones straddled over each other like an X may be used, with one set running off the feedback device and the other set of headphones connected to an irrelevant tape recording or similar non-feedback device.

Blinding the other hemisphere to reward may be necessary for functional improvements of a deficit system. Unihemispheric augmentation of neurotherapy may add surprising and powerful results. If anyone gives it a try, please let me know what you find.

References:

Broca, P. (1865), "Sur le siège de la faculté du langage articulé", Bulletin de la Société d'Anthropologie de Paris, 6, 377-393.

Coslett HB. (2007). Temporal processing deficits in letter-by-letter reading by Ingles and Eskes. J Int Neuropsychol Soc. 2007 Jan;13(1):108-9

Davidson RJ (1998). Anterior electrophysiological asymmetries, emotion, and depression: Conceptual and methodological conundrums. Psychophysiology, 35: 607-614.

Robinson, R. G. & Downhill, J. E. (1995). Lateralization of psychopathology in response to focal brain injury. In Brain asymmetry (eds R.J. Davidson & K. Hugdahl), 693-711, London: MIT Press.

Schiffer F (1997). Affect changes observed with right versus left lateral visual field stimulation in psychotherapy patients: possible physiological, psychological, and therapeutic implications. Comprehensive Psychiatry, 38, 289-95.

Zaidel, E. (1995) Interhemispheric transfer in the split brain: long term status following complete cerebral commissurotomy. In Brain asymmetry (eds R.J. Davidson & K. Hugdahl), 491-532, London: MIT Press.

-DK

News & Reviews NEW BOOKS

Epilepsy: A New Approach
by A Richard & J Reiter
Writer with epilepsy and a physician collaborate on this condition. --www.amazon.com/exec/obidos/ASIN/0802774652/eegspectrum

Social Neuroscience: People Thinking about Thinking People
by JT Cacioppo, PS Visser, CL Pickett (Eds)
Mental and brain function during social cognition, emotion, and behavior. --www.amazon.com/exec/obidos/ASIN/0262033356/eegspectrum

Addiction and Change: How Addictions Develop and Addicted People Recover
by Carlo C. DiClemente
Paradigm for understanding addictive behavior. --www.amazon.com/exec/obidos/ASIN/1593853440/eegspectrum

Parenting Children With Adhd: 10 Lessons That Medicine Cannot Teach
by Vincent J. Monastra
Balanced approach to treating children, including shoft-term medication when necessary. --www.amazon.com/exec/obidos/ASIN/1591471826/eegspectrum

Seizures and Epilepsy in Childhood: A Guide
by John M. Freeman, Eileen P. G. Vining, and Diana J. Pillas
Assists parents in a child's care who suffers from epilepsy --www.amazon.com/exec/obidos/ASIN/0801870518/eegspectrum

Treating Epilepsy Naturally : A Guide to Alternative and Adjunct Therapies
by Patricia A. Murphy
Treatment options and other information on epilepsy presented by one with the condition. --www.amazon.com/exec/obidos/ASIN/0658013793/eegspectrum

Mood Disorders: A Practical Guide
by S. Nassir Ghaemi
For clinicians - assists in diagnosing mood disorders. --www.amazon.com/exec/obidos/ASIN/0781727839/eegspectrum

The Female Brain
by Louann Brizendine
Neurohormonal and anatomical aspects of women. --www.amazon.com/exec/obidos/ASIN/0767920090/eegspectrum

Functional Connectivity of Frontal Cortex in ADHD Children : ADHD children show elevated coherence in lower alpha activity and reduced coherence in the upper alpha (10-11 Hz). www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17023555

Learning-disabled children treated with neurofeedback or placebo. : Two years after neurofeedback or placebo, EEG maturation was appropriate for the treated group, who also showed positive behavioral changes and LD remission symptoms. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=16929704

Self-regulation of Slow Cortical Potentials for ADHD : Slow cortical potential feedback appears to be "possibly efficacious" for ADHD children. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17060480

Severe mood dysregulation in children. : Severe mood dysregulation is not uncommon in childhood and places an individual at risk for early adulthood depression. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17056393

Disruption of cortical-limbic interaction as a substrate for comorbidity. : Prefrontal cortex dysfunction disrupts its ability to modulate the amygdala, making stressors more significant. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17062371

Cell density in the orbitofrontal cortex in alcohol dependence : Alcoholic dependent individuals show lower density of neurons and glial cells in Brodmann area 47. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17067348

Self-and Other-Assessments of Social Competence: Developmental Study. : With young children ADHD and depression was mediated by others' appraisal of social competence. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17066222

False lateralization of mesial temporal lobe epilepsy : Discrepancy between neurophysiological examinations and imaging indicates need for bilateral subdural electrode measurements for mTLE. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17062994

Will neuroimaging ever be used to diagnose pediatric bipolar disorder? : Current subjective diagnostic techniques such as those that rely on parent and child interview and symptomatic history may be replaced by brain imaging. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17064431

MRS detects brain injury and predicts cognitive function in TBI children : Longitudinal investigation of traumatic brain injury in children found neurometabolite ratios which correlated with neuropsychological performance. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17020480

Neural Synchrony in Brain Disorders : A wide range of disorder mights be explained by abnormalities in neuronal synchronization and temporal coordination. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17015233

ADHD involves differential cortical processing in visual spatial attention : ADHD may involve an unusual distribution of attentional resources at later stages of processing. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17000133

Dorsolateral prefrontal cortical activity in depression. : Brodmann area 9 were involved in depression, but the direction of activity changes varied. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17029760

EEG/fMRI measurements at 7 Tesla using a new EEG cap. : Co-registration technology improvements are discussed. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17035045

DSM-IV alcohol dependence: a categorical or dimensional phenotype? : Diagnoses are necessary for clinical practice decisions, but dimensions of alcohol-dependence are helpful in research. www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17038207

I answered that comodulation was as superior to coherence as length is superior to height.

I was being fictitious and explained myself, though who knows what ever comes across at these meetings. I tried to convey the idea that a measure's superiority depends entirely upon what is being measured and why. Cartographers care about the length of a river, for instance, for their maps but those caught in its flood plain during a storm care little about its length and only about its height. I recently read that the Amazon is the shortest major river in the world -- in height! In width and length, of course, it is one of the largest.

So the real question with comodulation versus coherence is not one of intrinsic value but one's goal in making a measurement. What do you want to know? For certain brain functions magnitude consistency between brain areas may be more important; for other functions, phase consistency is. And ironically, due to the organization of cortical networks, each measure often overlaps the other, so in many cases there is no clear preference.

The comparison of comodulation to coherence has already yielded some fruit, however. It underlines the two-dimensionality of spectral analysis. A stationary rhythm requires at least two bits of information to be reproduced, its magnitude and its phase. When two similar rhythms are compared, they too can be similar on magnitude or phase, or both. Comodulation and coherence are consistency measures of magnitude and phase, and "phase" as it is called, and unity, my name for magnitude difference, are the combined differences between sites divided by time. These four indices capture all of the information shared between two stationary signals for each frequency band. However, what is we are interested in the relationship between frequency bands. Then instead of examining shared information between TWO SITES in a SINGLE FREQUENCY range, we examine shared information between TWO FREQUENCIES at a SINGLE SITE. Same frequency different sites, or same site different frequencies. This more than doubles the possible information domain we might examine.

Two frequencies-one site also can be quantified by four indices for stationary signals: bimodulation (magnitude consistency) and band ratio (magnitude or power differences) in the energy domain; dual frequency coherence (phase consistency) and dual frequency phase (difference) in the phase domain. If the theta and alpha bands bimodulate, for instance, at site Pz, it may mean that the individual's dominant frequency straddles these bands. If theta and alpha do not bimodulate, it means each rhythm waxes and wanes independently of the other, which has psychophysiological significance. Bimodulation as well as band ratio may quantify the extent of the dominant frequency, its integrity, or other functional aspects of the thalamocortical network. Rhythm independence could denote health or pathology -- we have to figure this out. Dual frequency coherence also addresses the same issues, albeit in the phase domain. (I prefer the term "bicoherence" to "dual frequency" but, alas, bicoherence was already taken as a measure of mutual information between two frequencies that involves computation of a 3rd joint frequency).

And if we lift up our pivot foot, to use a basketball metaphor, and walk around the site-frequency plane, we create entirely new spectral parameter, psychophysiologically meaningful or not, we do not yet know. Where before we had two sites-one frequency (e.g., coherence, comodulation), or two frequencies-one site (e.g., band ratio), we can also look at any 2x2, two frequencies and two sites, if we don't mind stepping into quicksand. I call it quicksand, this near-infinite problemspace, because we have to much permutational freedom to find anything relevant. In a 2x2 approach we can examine phase or magnitude consistency between 7 Hz at P3 and 5 Hz at P4, i.e., cross-dual-frequency coherence or cross-bimodulation, respectively, or between any of the 18 factorial site pairs for the 10-20 electrode position system multiplied by, conservatively, 40 factorial frequencies pairs. This is a haystack in search of a needle. And let's not jump into using the 10-10 electrode system until 31 factorial gets smaller.... And as long as we're moving up to 2x2, why limit our permutations there, when 3x1s (triherence and trimodulation, phase consistency between three sites for one band) and 3x2s (cross-triherence) are waiting in the wings. Any NxN. It took 10 years for comodulation to gain some acceptance -- who has the years necessary to identify a reliable correspondence between even a 2x2 and psychophysiology? Does frontal theta phase lose coherence with the posterior alpha phase? That is the only easy picking I see in the 2x2 problem space, along with homologous comparisons. Well, maybe there will be some fruit from those comparisons, but mostly our connectivity measures are tethered to one tentpole and "cross" topography or frequency but never both simultaneously.

That said, we should keep in mind that comodulation, coherence, and any feasible assortment of spectral indices are but a few of the parameters that may relate brain function to mental function. Non-spectral measures, or medians and other derivatives such as slope or variability, mobility or complexity may prove useful in mapping brain to mind. Quantitative EEG needs to incorporate some of the promising new approaches to shed more light on the informational vortex that envelopes brain behavior. To date, it has barely scratched the surface.

-DK