EEG recurrence markers and sleep quality.

Objectives: To show that EEG markers formed using the variable percent recurrence reliably quantified two related aspects of sleep quality, sleep depth and sleep fragmentation. As hypotheses, the depth marker would increase and the fragmentation marker decrease in patients where improved sleep quality occurred when assessed by polysomnography.

Methods: The patients (N=20) had been diagnosed with obstructive sleep apnea during diagnostic polysomnography (dPSG), and had exhibited increased REM sleep (clinical indication of improved sleep quality) during subsequent polysomnography to titrate the pressure of a treatment device (cPSG).

Continuous EEG-based dynamic markers for sleep depth and phasic events.

Sleep architecture is characterized by classifying polysomnographic epochs into mutually exclusive stages. Notwithstanding the clinical importance of staging, it has the drawback of representing sleep as a discrete process. Metrics based on the electroencephalogram (EEG) are needed to supplement conventional sleep staging by allowing a description of sleep in terms of unitary, continuous markers.

Increased determinism in brain electrical activity occurs in association with multiple sclerosis.

Objective: Increased determinism (decreased complexity) of brain electrical activity has been associated with some brain diseases. Our objective was to determine whether a similar association occurred for multiple sclerosis (MS).

Methods: Ten subjects with a relapsing-remitting course of MS who were in remission were studied; the controls were age- and gender-matched clinically normal subjects.

Electromagnetic hypersensitivity: evidence for a novel neurological syndrome.

Objective: We sought direct evidence that acute exposure to environmental-strength electromagnetic fields (EMFs) could induce somatic reactions (EMF hypersensitivity).

Methods: The subject, a female physician self-diagnosed with EMF hypersensitivity, was exposed to an average (over the head) 60-Hz electric field of 300 V/m (comparable with typical environmental-strength EMFs) during controlled provocation and behavioral studies.

Results: In a double-blinded EMF provocation procedure specifically designed to minimize unintentional sensory cues, the subject developed temporal pain, headache, muscle twitching, and skipped heartbeats within 100 s after initiation of EMF exposure (p < .

Transient and steady-state magnetic fields induce increased fluorodeoxyglucose uptake in the rat hindbrain.

We inquired into the biophysical basis of the ability of weak electromagnetic fields (EMFs) to trigger onset and offset evoked potentials, and to produce steady-state changes in the electroencephalogram (EEG). Rats were exposed to a 2.5-G, 60-Hz magnetic field and the neuroanatomical region of glucose activation associated with the effect of the field on the EEG was identified by positron emission tomography (PET) using fluorodeoxyglucose (FDG).

Simulated MR magnetic field induces steady-state changes in brain dynamics: Implications for interpretation of functional MR studies.

We examined whether a magnetic field comparable to one of the fields produced during MRI induced steady-state changes in brain electrical activity while the field was applied (called a presence effect to distinguish it from evoked potentials). The electroencephalogram was measured from standard scalp locations in the presence and absence of 100-200 microT, 60 Hz, and the effect of the field was evaluated by nonlinear (recurrence analysis) and linear techniques; individual subjects served as their own controls. Using recurrence analysis, changes in brain activity lasting 1 sec (the longest interval considered) were found in 21 of 22 subjects (P < 0.

Numerical analysis of recurrence plots to detect effect of environmental-strength magnetic fields on human brain electrical activity.

Environmental magnetic fields may activate the neuroendocrine stressor system leading to some human diseases. The stressor theory predicts that the fields can trigger changes in brain electrical activity, like known stressors. We exposed subjects to 1 and 5 μT, 60 Hz while recording electroencephalograms (EEGs) from six derivations, and used a novel method based on numerical analysis of recurrence plots computed from the signals to detect brain electrical potentials evoked by onset and/or offset of the field.

Multiple sclerosis impairs ability to detect abrupt appearance of a subliminal stimulus.

Objectives: The study was designed to find evidence that brain electrical activity associated with processing the abrupt appearance or disappearance of a sensory stimulus differed in the presence and absence of the neuropathological changes that are characteristic of multiple sclerosis (MS).

Methods: A subliminal stimulus (electrical field) was applied, and the onset and offset responses from patients with MS were compared with the responses of study participants in two age- and gender-matched control groups, using a novel type of non-linear dynamical analysis that had been developed in earlier studies.

Results: An onset response occurred in 27% of the patients with MS, compared with 85% in the control groups.

The effects of mobile-phone electromagnetic fields on brain electrical activity: a critical analysis of the literature.

We analyzed the reports in which human brain electrical activity was compared between the presence and absence of radio-frequency and low-frequency electromagnetic fields (EMFs) from mobile phones, or between pre- and post-exposure to the EMFs. Of 55 reports, 37 claimed and 18 denied an EMF-induced effect on either the baseline electro encephalogram (EEG), or on cognitive processing of visual or auditory stimuli as reflected in changes in event-related potentials. The positive reports did not adequately consider the family-wise error rate, the presence of spike artifacts in the EEG, or the confounding role of the two different EMFs.

Mobile-phone pulse triggers evoked potentials.

If mobile-phone electromagnetic fields (EMFs) are hazardous, as suggested in the literature, processes or mechanisms must exist that allow the body to detect the fields. We hypothesized that the low-frequency pulses produced by mobile phones (217 Hz) were detected by sensory transduction, as evidenced by the ability of the pulses to trigger evoked potentials (EPs). Electroencephalograms (EEGs) were recorded from six standard locations in 20 volunteers and analyzed to detect brain potentials triggered by a pulse of the type produced by mobile phones.

The electric field is a sufficient physical determinant of the human magnetic sense.

Purpose: The onset and offset of weak low-frequency magnetic fields triggered evoked potentials in human subjects that could be detected using nonlinear analysis, but not by means of time averaging. Because the magnetic fields and their induced electric fields were both present in the brain, their respective role in producing the effect on brain activity could not be ascertained. We inquired whether a biophysical coupling mechanism involving only the electric field could explain the occurrence of the brain potentials.

Evidence that transduction of electromagnetic field is mediated by a force receptor.

Low-strength magnetic fields triggered onset and offset evoked potentials, indicating that the detection process was a form of sensory transduction; whether the field interacted directly with an ion channel or indirectly via a signaling cascade is unknown. By analogy with electrosensory transduction in lower life forms, we hypothesized that the evoked potentials were initiated by a force exerted by the induced electric field on an ion channel in the plasma membrane. We applied a rapid magnetic stimulus (0.

Magnetosensory function in rats: localization using positron emission tomography.

The aim of this study was to show that low-strength electromagnetic fields (EMFs) produced evoked potentials in rats and to localize the activated region in the brain. In response to a 2.5-G, 60-Hz stimulus, onset- and offset-evoked potentials were detected (P < 0.

Method for detection of changes in the EEG induced by the presence of sensory stimuli.

The onset and offset of sensory stimuli evoke transient changes in the electroencephalogram (EEG) that can be detected by linear and/or nonlinear analysis. However, there is presently no systematic procedure to quantify the brain-electrical-activity correlate of the presence of a stimulus (as opposed to its onset evoked potential). We describe a method for detecting a stimulus-related change in brain electrical activity that persists while the stimulus is present (presence effect).

The effects of low-frequency environmental-strength electromagnetic fields on brain electrical activity: a critical review of the literature.

Reports dealing with the stimulus-response relationship between low-level, low-frequency electromagnetic fields (EMFs) and changes in brain electrical activity permit assessment of the hypothesis that EMFs are detected by the body via the process of sensory transduction. These reports, as well as those involving effects on brain activity observed after a fixed time of exposure, are critically reviewed here. A consistent stimulus-response relationship between EMFs and changes in brain activity has been demonstrated in animal and human subjects.

Magnetosensory evoked potentials: consistent nonlinear phenomena.

Electromagnetic fields (EMFs) having strengths typically found in the general environment can alter brain activity, but the reported effects have been inconsistent. We theorized that the problem arose from the use of linear methods for analyzing what were actually nonlinear phenomena, and therefore studied whether the nonlinear signal-processing technique known as recurrence quantification analysis (RQA) could be employed as the basis of a reliable method for demonstrating consistent changes in brain activity. Our primary purpose was to develop such a method for observing the occurrence of evoked potentials in individual subjects exposed to magnetic fields (2G, 30 and 60 Hz).

Nonlinear EEG activation evoked by low-strength low-frequency magnetic fields.

Recent electrophysiological evidence suggested the existence of a human magnetic sense, but the kind of dynamical law that governed the stimulus-response relationship was not established. We tested the hypothesis that brain potentials evoked by the onset of a weak, low-frequency magnetic field were nonlinearly related to the stimulus. A field of 1G, 60 Hz was applied for 2s, with a 5s inter-stimulus period, and brain potentials were recorded from occipital electrodes in eight subjects, each of whom were measured twice, with at least 1 week between measurements.

Detection of nonlinear event-related potentials.

The methods used to evaluate event-related potentials (ERPs) are generally insensitive to nonlinear responses. Our goal was to show that nonlinear ERPs could be detected using recurrence analysis (RA). When fixed-phase sine signals were added to baseline electroencephalograms (EEGs), the added linear determinism was detected by signal averaging, as expected, and by RA.