First, surface ZNF involves measuring the amplitude of neurons directly beneath the electrode, where 95% of the neurons arise from a distance of 6 cm, and all frequencies are mixed together at each electrode. LZNF uses 3-D source localization applied to human QEEG in which the mixture of frequencies under each scalp electrode is unscrambled and linked to sources in the interior of the brain with accuracies of approximately 1 cm.
Second, surface ZNF calculates the z score of identified EEG metrics at various 10-20 surface electrode sites, whereas with LZNF, the z score is calculated for a particular collection of current source density voxels. This makes it possible to conduct neurofeedback with the z scores of the calculated location of deeper cortical dipole generating regions or structures (eg, Brodmann areas, cingulate gyrus, precuneus) and allows for more neuroregulation and enhanced QEEG normalization. Consequently, clinical reports of LZNF suggest that positive outcomes can be achieved with an average of 10 to 20 sessions compared with other types of neurofeedback that can require as many as 80 sessions.29,32,33
In a retrospective study of children and adults with ADHD, 19ZNF was utilized for all pre- and post-comparisons.34 Statistically significant differences were seen in constructs of attention, executive function, behavior, and electrocortical functioning (P = .000-.008; ES = 1.29-3.42 for attention and hyperactivity). These results were achieved with 10 to 15 sessions compared with 40 or more sessions usually required for SMR, SCP, and TBR.
Using LZNF, brain networks and hubs can be identified and targeted as regions of interest for training. By directly targeting these regions of interest, in a z-score framework, LZNF allows for specificity and localization similar to that of fMRI. As brain regions (with deviant z scores) are identified and reinforced toward the mean, the changes in the hubs and connections between hubs can be monitored and correlated to improvements in the clinical symptoms.32,33
In a randomized, double-blind, placebo-controlled study using the LORETA phase neurofeedback for 30 minutes, significant changes were seen in the default mode network and the attention network (P < .001).35 In a study by Bauer and colleagures,36 EEG topographies were analyzed by LORETA. Feedback was strictly related to generating sources that have their center (ie, local current density maximum voxels) located within the preselected region of training. Significantly enhanced activity was seen in the left linguistic area of participants who had received neurofeedback (P < .01).
Safety and effectiveness
Overall safety concerns have been few. However, lack of individualization of treatment by inexperienced practitioners who merely put on electrodes without proper evaluation may be an important element in causing iatrogenic effects. Adverse effects include manic behavior; anger and irritability; increases in depression, anxiety, and agitation; fatigue; sleep disturbance; emotional lability; OCD symptoms; tics; enuresis; somatic symptoms; decline in cognitive functioning; temporary disorientation or dissociation; and incontinence.37
Proper training and board certification in neurofeedback are encouraged by the Biofeedback Certification International Alliance.38 If neurofeedback is used to treat epilepsy or in patients with a history of seizures, a neurologist should co-partner with the clinician to monitor the risk of inducing seizures. Although there are no reports in the literature, many clinicians have reported that medication adverse effects may worsen with neurofeedback, which may indicate that medications are less necessary as brain functions improve. In this case, the medication dosage may be lowered as neurofeedback continues. Future studies should pay particular attention to any adverse effects that may occur during neurofeedback.
Dr. Simkin is Clinical Assistant Professor, Department of Psychiatry, Emory University School of Medicine, Atlanta, GA. Dr. Lubar is Professor Emeritus, Department of Psychology, University of Tennessee, Knoxville, TN; and Affiliate Scientist for the Center of Complex Systems and Brain Sciences, Charles E. Schmidt College of Science, Florida Atlantic University, Boca Raton, FL.
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