Myoung Soo Kwon

Effects of mobile phone electromagnetic fields: critical evaluation of behavioral and neurophysiological studies.

For the last two decades, a large number of studies have investigated the effects of mobile phone radiation on the human brain and cognition using behavioral or neurophysiological measurements. This review evaluated previous findings with respect to study design and data analysis. Provocation studies found no evidence of subjective symptoms attributed to mobile phone radiation, suggesting psychological reasons for inducing such symptoms in hypersensitive people. Behavioral studies previously reported improved cognitive performance under exposure, but it was likely to have occurred by chance due to multiple comparisons. Recent behavioral studies and replication studies with more conservative statistics found no significant effects compared with original studies. Neurophysiological studies found no significant effects on cochlear and brainstem auditory processing, but only inconsistent results on spontaneous and evoked brain electrical activity. The inconsistent findings suggest possible false positives due to multiple comparisons and thus replication is needed. Other approaches such as brain hemodynamic response measurements are promising but the findings are few and not yet conclusive. Rigorous study design and data analysis considering multiple comparisons and effect size are required to reduce controversy in this important field of research.

GSM mobile phone radiation suppresses brain glucose metabolism

We investigated the effects of mobile phone radiation on cerebral glucose metabolism using high-resolution positron emission tomography (PET) with the 18F-deoxyglucose (FDG) tracer. A long half-life (109 minutes) of the 18F isotope allowed a long, natural exposure condition outside the PET scanner. Thirteen young right-handed male subjects were exposed to a pulse-modulated 902.4 MHz Global System for Mobile Communications signal for 33 minutes, while performing a simple visual vigilance task. Temperature was also measured in the head region (forehead, eyes, cheeks, ear canals) during exposure. 18F-deoxyglucose PET images acquired after the exposure showed that relative cerebral metabolic rate of glucose was significantly reduced in the temporoparietal junction and anterior temporal lobe of the right hemisphere ipsilateral to the exposure. Temperature rise was also observed on the exposed side of the head, but the magnitude was very small. The exposure did not affect task performance (reaction time, error rate). Our results show that short-term mobile phone exposure can locally suppress brain energy metabolism in humans.

Fast parametric evaluation of central speech-sound processing with mismatch negativity (MMN)

The aim of this study was to develop a paradigm for obtaining a multi-feature profile for central auditory processing of different magnitudes of prosodic and phonetic changes in speech sounds. We recorded the MMNs to three vowel identity changes, three magnitudes of changes in intensity, and vowel duration as well as to two magnitudes of pitch changes from semi-synthetic vowels in 34min. Furthermore, we examined how the type and magnitude of deviation affect the size and timing of the MMN. All sound changes elicited statistically significant MMN responses, with the MMN amplitudes increasing with an increase in sound deviance. Importantly, the MMN amplitudes for the vowel changes reflected the differences between the phonemes, as did the MMNs to vowel-duration changes reflect the categorization of these sounds to short and long vowel categories, which are meaningful in the Finnish language. This new multi-feature MMN paradigm is suitable for investigating the central auditory processing of different magnitudes of speech-sound changes and can be used, for instance, in the investigation of pre-attentive phoneme categorization. The paradigm is especially useful for studying speech and language disorders in general, language development, and evolution of phoneme categories early in life, as well as brain plasticity during native or second language learning.

No effects of mobile phone use on cortical auditory change‐detection in children: An ERP study

We investigated the effect of mobile phone use on the auditory sensory memory in children. Auditory event-related potentials (ERPs), P1, N2, mismatch negativity (MMN), and P3a, were recorded from 17 children, aged 11-12 years, in the recently developed multi-feature paradigm. This paradigm allows one to determine the neural change-detection profile consisting of several different types of acoustic changes. During the recording, an ordinary GSM (Global System for Mobile Communications) mobile phone emitting 902 MHz (pulsed at 217 Hz) electromagnetic field (EMF) was placed on the ear, over the left or right temporal area (SAR(1g) = 1.14 W/kg, SAR(10g) = 0.82 W/kg, peak value = 1.21 W/kg). The EMF was either on or off in a single-blind manner. We found that a short exposure (two 6 min blocks for each side) to mobile phone EMF has no statistically significant effects on the neural change-detection profile measured with the MMN. Furthermore, the multi-feature paradigm was shown to be well suited for studies of perception accuracy and sensory memory in children. However, it should be noted that the present study only had sufficient statistical power to detect a large effect size.

Preattentive auditory information processing under exposure to the 902 MHz GSM mobile phone electromagnetic field: A mismatch negativity (MMN) study

Previous studies on the effects of the mobile phone electromagnetic field (EMF) on various event-related potential (ERP) components have yielded inconsistent and even contradictory results, and often failed in replication. The mismatch negativity (MMN) is an auditory ERP component elicited by infrequent (deviant) stimuli differing in some physical features from the repetitive frequent (standard) stimuli in a sound sequence. The MMN provides a sensitive measure for cortical auditory stimulus feature discrimination, regardless of attention and other contaminating factors. In this study, MMN responses to duration, intensity, frequency, and gap changes were recorded in healthy young adults (n = 17), using a multifeature paradigm including several types of auditory change in the same stimulus sequence, while a GSM mobile phone was placed on either ear with the EMF (902 MHz pulsed at 217 Hz; SAR(1g) = 1.14 W/kg, SAR(10g) = 0.82 W/kg, peak value = 1.21 W/kg, measured with an SAM phantom) on or off. An MMN was elicited by all deviant types, while its amplitude and latency showed no significant differences due to EMF exposure for any deviant types. In the present study, we found no conclusive evidence that acute exposure to GSM mobile phone EMF affects cortical auditory change detection processing reflected by the MMN.

Risk-Taking Behavior in a Computerized Driving Task: Brain Activation Correlates of Decision-Making, Outcome, and Peer Influence in Male Adolescents

Increased propensity for risky behavior in adolescents, particularly in peer groups, is thought to reflect maturational imbalance between reward processing and cognitive control systems that affect decision-making. We used functional magnetic resonance imaging (fMRI) to investigate brain functional correlates of risk-taking behavior and effects of peer influence in 18–19-year-old male adolescents. The subjects were divided into low and high risk-taking groups using either personality tests or risk-taking rates in a simulated driving task. The fMRI data were analyzed for decision-making (whether to take a risk at intersections) and outcome (pass or crash) phases, and for the influence of peer competition. Personality test-based groups showed no difference in the amount of risk-taking (similarly increased during peer competition) and brain activation. When groups were defined by actual task performance, risk-taking activated two areas in the left medial prefrontal cortex (PFC) significantly more in low than in high risk-takers. In the entire sample, risky decision-specific activation was found in the anterior and dorsal cingulate, superior parietal cortex, basal ganglia (including the nucleus accumbens), midbrain, thalamus, and hypothalamus. Peer competition increased outcome-related activation in the right caudate head and cerebellar vermis in the entire sample. Our results suggest that the activation of the medial (rather than lateral) PFC and striatum is most specific to risk-taking behavior of male adolescents in a simulated driving situation, and reflect a stronger conflict and thus increased cognitive effort to take risks in low risk-takers, and reward anticipation for risky decisions, respectively. The activation of the caudate nucleus, particularly for the positive outcome (pass) during peer competition, further suggests enhanced reward processing of risk-taking under peer influence.

No effects of short-term GSM mobile phone radiation on cerebral blood flow measured using positron emission tomography.

The present study investigated the effects of 902.4 MHz global system for mobile communications (GSM) mobile phone radiation on cerebral blood flow using positron emission tomography (PET) with the (15) O-water tracer. Fifteen young, healthy, right-handed male subjects were exposed to phone radiation from three different locations (left ear, right ear, forehead) and to sham exposure to test for possible exposure effects on brain regions close to the exposure source. Whole-brain [¹⁵O]H₂O-PET images were acquired 12 times, 3 for each condition, in a counterbalanced order. Subjects were exposed for 5 min in each scan while performing a simple visual vigilance task. Temperature was also measured in the head region (forehead, eyes, cheeks, ear canals) during exposure. The exposure induced a slight temperature rise in the ear canals but did not affect brain hemodynamics and task performance. The results provided no evidence for acute effects of short-term mobile phone radiation on cerebral blood flow.

Neglect is a Spatial Failure of Alerting Mechanisms Required for Awareness: An ERP Study

In the present study, we describe a group of right brain-damaged (RBD) patients with neglect or extinction, most of them affected in all three (visual, auditory, somatosensory) modalities studied. We applied event-related potential (ERP) analysis to reveal the neural mechanisms underlying hemispatial neglect. ERPs to stimuli of all three modalities were determined for the patients with neglect/extinction at (sub)acute phase, and 3 and 12 months post-stroke. Our results demonstrated that N1 deflections in ERPs, reflecting fronto-parietal alerting mechanisms, were absent or diminished/delayed in neglect, and the waves became normalized with recovery from neglect. In somatosensory ERPs, similar changes were evident also in P1 deflections preceding the N1, reflecting activation of the secondary somatosensory cortex (SII). We also demonstrated somatosensory ERPs of some of our patients who showed different responses elicited by low intensity electrical stimulation of the median nerve at the wrist depending on the location of the hands either in uncrossed anatomical position or crossed over the body midline to the other hemispace. Our results indicate that there are cases among patients with hemispatial neglect who do indeed show emergence or increment of responses to left-hand stimulation when the arm is crossed to the right hemispace. Therefore, we propose that the mechanism underlying hemispatial neglect is the disruption of the flow of (location related) sensory information to awareness at the level of multimodal alerting mechanisms.

Automatic auditory change detection in humans is influenced by visual-auditory associative learning.

Automatic detection of auditory changes that violate a regular sound sequence is indexed by the mismatch negativity (MMN) component of the event-related potential. The MMN is considered to reflect an auditory sensory memory and attention switching mechanism. Our aim was to study whether the auditory MMN can be associated with visual cues that have predictive value. By using visual cues that predicted the appearance of a deviant sound in most but not all of the cases, we were able to elicit MMN not only to the deviant sounds but also to those regular sounds that were misleadingly preceded by the visual cue. This result indicates high flexibility in the human automatic auditory change detection system, as it is affected by short-term visual–auditory associative learning.