Does the short-term exposure to radiofrequency electromagnetic field originating from mobile phone affect auditory functions as measured by Acoustic Admittance and Evoked Otoacoustic Emission tests?

BACKGROUND: Mobile phones constitute an important source of radiofrequency electromagnetic field (RF-EMF) for humans. Taking into account high sensitivity of sensory hair cells of the inner ear to endogenous and exogenous agents, the potential impact of mobile phone usage on auditory organs is of particular interest. AIM: The aim of the study was to evaluate the impact of short-term exposure to RF-EMF generated by a mobile phone during 15-minute simulated phone call on human hearing as measured by Transient Evoked Otoacoustic Emission (TEOAE) and Acoustic Admittance Testing (AAT). MATERIAL AND METHODS: Within-subject study was performed on 23 healthy volunteers. All of the participants underwent TEOAE and AAT before and immediately after 15-minute simulated phone call with the use of a standard, modern smartphone. Analyzed parameters included: static compliance of tympanic membrane, middle ear pressure, ipsi- and contralateral acoustic reflex thresholds and percentage of signal reproducibility in TEOAE for exposed and non-exposed ear. Additionally, the results were compared in subgroups distinguished basing on self-reported sensitivity to RF-EMF originating from mobile phones. RESULTS: No statistically significant differences were identified between results of TEOAE and AAT before and after exposure, both in exposed and non-exposed ear. The results of EMF sensitive and non-sensitive subjects were comparable in all performed tests. CONCLUSIONS: Short-term exposure to mobile phone electromagnetic field did not influence auditory functions as measured by Evoked Otoacoustic Emission test and Acoustic Admittance Testing.

Light Effects on Behavioural Performance Depend on the Individual State of Vigilance.

Research has shown that exposure to bright white light or blue-enriched light enhances alertness, but this effect is not consistently observed in tasks demanding high-level cognition (e.g., Sustained Attention to Response Task-SART, which measures inhibitory control). Individual differences in sensitivity to light effects might be mediated by variations in the basal level of arousal. We tested this hypothesis by measuring the participants' behavioural state of vigilance before light exposure, through the Psychomotor Vigilance Task. Then we compared the effects of a blue-enriched vs. dim light at nighttime on the performance of the auditory SART, by controlling for individual differences in basal arousal. The results replicated the alerting effects of blue-enriched light, as indexed by lower values of both proximal temperature and distal-proximal gradient. The main finding was that lighting effects on SART performance were highly variable across individuals and depended on their prior state of vigilance. Specifically, participants with higher levels of basal vigilance before light exposure benefited most from blue-enriched lighting, responding faster in the SART. These results highlight the importance of considering basal vigilance to define the boundary conditions of light effects on cognitive performance. Our study adds to current research delineating the complex and reciprocal interactions between lighting effects, arousal, cognitive task demands and behavioural performance.

Auditory late effects of childhood cancer therapy: a report from the Children's Oncology Group.

Children treated for malignancies may be at risk for early- or delayed-onset hearing loss that can affect learning, communication, school performance, social interaction, and overall quality of life. Survivors at particular risk include those treated with platinum compounds (cisplatin and/or carboplatin) for neuroblastoma, hepatoblastoma, osteosarcoma, or germ-cell tumors and/or those treated with radiation that affects the ear at doses of >30 Gy for pediatric head and neck tumors. The aims of the Auditory/Hearing Late Effects Task Force of the Children's Oncology Group in this report were to (1) review ototoxicity resulting from childhood cancer therapy including platinum compounds (cisplatin and carboplatin) and radiation, (2) describe briefly cochlear pathophysiology and genetics of cisplatin-related hearing loss, (3) explain the impact of hearing loss resulting from chemotherapy and radiation, and (4) offer recommendations regarding evaluation and management of pediatric patients who are at risk for treatment-related hearing loss. A questionnaire is included as a tool to assist pediatricians in assessment.

Differences in electric brain responses to melodies and chords.

The music we usually listen to in everyday life consists of either single melodies or harmonized melodies (i.e., of melodies "accompanied" by chords). However, differences in the neural mechanisms underlying melodic and harmonic processing have remained largely unknown. Using EEG, this study compared effects of music-syntactic processing between chords and melodies. In melody blocks, sequences consisted of five tones, the final tone being either regular or irregular (p = .5). Analogously, in chord blocks, sequences consisted of five chords, the final chord function being either regular or irregular. Melodies were derived from the top voice of chord sequences, allowing a proper comparison between melodic and harmonic processing. Music-syntactic incongruities elicited an early anterior negativity with a latency of approximately 125 msec in both the melody and the chord conditions. This effect was followed in the chord condition, but not in the melody condition, by an additional negative effect that was maximal at approximately 180 msec. Both effects were maximal at frontal electrodes, but the later effect was more broadly distributed over the scalp than the earlier effect. These findings indicate that melodic information (which is also contained in the top voice of chords) is processed earlier and with partly different neural mechanisms than harmonic information of chords.

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.

Repetitive transcranial magnetic stimulation improve tinnitus in normal hearing patients: a double-blind controlled, clinical and neuroimaging outcome study.

BACKGROUND AND PURPOSE: Tinnitus is a frequent disorder which is very difficult to treat and there is compelling evidence that tinnitus is associated with functional alterations in the central nervous system. Targeted modulation of tinnitus-related cortical activity has been proposed as a promising new treatment approach. We aimed to investigate both immediate and long-term effects of low frequency (1 Hz) repetitive transcranial magnetic stimulation (rTMS) in patients with tinnitus and normal hearing. METHODS: Using a parallel design, 20 patients were randomized to receive either active or placebo stimulation over the left temporoparietal cortex for five consecutive days. Treatment results were assessed by using the Tinnitus Handicap Inventory. Ethyl cysteinate dimmer-single photon emission computed tomography (SPECT) imaging was performed before and 14 days after rTMS. RESULTS: After active rTMS there was significant improvement of the tinnitus score as compared to sham rTMS for up to 6 months after stimulation. SPECT measurements demonstrated a reduction of metabolic activity in the inferior left temporal lobe after active rTMS. CONCLUSION: These results support the potential of rTMS as a new therapeutic tool for the treatment of chronic tinnitus, by demonstrating a significant reduction of tinnitus complaints over a period of at least 6 months and significant reduction of neural activity in the inferior temporal cortex, despite the stimulation applied on the superior temporal cortex.

Effects of UMTS cellular phones on human hearing: results of the European project EMFnEAR.

Abstract The European project EMFnEAR was undertaken to assess potential changes in human auditory function after a short-term exposure to radiofrequency (RF) radiation produced by UMTS (Universal Mobile Telecommunication System) mobile phones. Participants were healthy young adults with no hearing or ear disorders. Auditory function was assessed immediately before and after exposure to radiofrequency radiation, and only the exposed ear was tested. Tests for the assessment of auditory function were hearing threshold level (HTL), distortion product otoacoustic emissions (DPOAE), contralateral suppression of transiently evoked otoacoustic emission (CAS effect on TEOAE), and auditory evoked potentials (AEP). The exposure consisted of speech at a typical conversational level delivered via an earphone to one ear, plus genuine or sham RF-radiation exposure produced by a commercial phone controlled by a personal computer. Results from 134 participants did not show any consistent pattern of effects on the auditory system after a 20-min UMTS exposure at the maximum output of the phone with 69 mW/kg SAR in the cochlea region in a double blind comparison of genuine and sham exposure. An isolated effect on the hearing threshold at high frequencies was identified, but this was statistically nonsignificant after correction for multiple comparisons. It is concluded that UMTS short-term exposure at the maximum output of consumer mobile phones does not cause measurable immediate effects on the human auditory system.

Generalized model of the microwave auditory effect.

A generalized theoretical model for evaluating the amplitudes of the sound waves generated in a spherical head model, which is irradiated by microwave pulses, is developed. The thermoelastic equation of motion is solved for a spherically symmetric heating pattern of arbitrary form. For previously treated heating patterns that are peaked at the sphere centre, the results reduce to those presented before. The generalized model is applied to the case in which the microwave absorption is concentrated near the sphere surface. It is found that, for equal average specific absorption rates, the sound intensity generated by a surface localized heating pattern is comparable to that generated by a heating pattern that is peaked at the centre. The dependence of the induced sound pressure on the shape of the microwave pulse is explored. Another theoretical extension, to the case of repeated pulses, is developed and applied to the interpretation of existing experimental data on the dependence of the human hearing effect threshold on the pulse repetition frequency.

[Dependence of acoustic-motor reaction of healthy individuals from geomagnetic activity].

During February-April, 2008 using special computer test, a daily monitoring of simple acoustic-motor reaction was carried out in 18 healthy tested individuals. We found a significant decrease in the speed of acoustic-motor reaction the day before and the same day geomagnetic disturbance occurred, as well as the same and 2-3 days after a geomagnetic calm occurred. Presumably, either an essential increase or a decreases of geomagnetic activity are adverse factors for the functional state of a central nervous system.

TMS modulation of visual and auditory processing in the posterior parietal cortex.

Audio-visual stimuli typically yield faster responses than isolated modality-specific ones. This crossmodal speed advantage depends upon efficient multisensory integration mechanisms in the brain. Here, we used repetitive transcranial magnetic stimulation (rTMS) to address the role of the posterior parietal cortex, in particular of the inferior parietal lobule (IPL), in speeding up responses to crossmodal stimuli. The results show that rTMS over IPL impairs the response to contralateral modality-specific visual and auditory targets without affecting the response speed advantage following audio-visual targets. Furthermore, this speed advantage is subserved by a neural coactivation mechanism suggesting a summation in a given neural site. Control rTMS over V1 impaired only contralateral visual responses without affecting the response to auditory or audio-visual targets. These results suggest that the response speed advantage for crossmodal targets is maintained in spite of the IPL interference that impairs modality-specific responses. The possible role of alternative sites for the audio-visual advantage, such as the superior colliculus, is discussed.

Cochlear-implant high pulse rate and narrow electrode configuration impair transmission of temporal information to the auditory cortex.

In the most commonly used cochlear prosthesis systems, temporal features of sound are signaled by amplitude modulation of constant-rate pulse trains. Several convincing arguments predict that speech reception should be optimized by use of pulse rates > or approximately 2,000 pulses per second (pps) and by use of intracochlear electrode configurations that produce restricted current spread (e.g., bipolar rather than monopolar configurations). Neither of those predictions has been borne out in consistent improvements in speech reception. Neurons in the auditory cortex of anesthetized guinea pigs phase lock to the envelope of sine-modulated electric pulse trains presented through a cochlear implant. The present study used that animal model to quantify the effects of carrier pulse rate, electrode configuration, current level, and modulator wave shape on transmission of temporal information from a cochlear implant to the auditory cortex. Modulation sensitivity was computed using a signal-detection analysis of cortical phase-locking vector strengths. Increasing carrier pulse rate in 1-octave steps from 254 to 4,069 pps resulted in systematic decreases in sensitivity. Comparison of sine- versus square-wave modulator waveforms demonstrated that some, but not all, of the loss of modulation sensitivity at high pulse rates was a result of the decreasing size of pulse-to-pulse current steps at the higher rates. Use of a narrow bipolar electrode configuration, compared with the monopolar configuration, produced a marked decrease in modulation sensitivity. Results from this animal model suggest explanations for the failure of high pulse rates and/or bipolar electrode configurations to produce hoped-for improvements in speech reception.

Effects of the task of categorizing FM direction on auditory evoked magnetic fields in the human auditory cortex.

We examined effects of the task of categorizing linear frequency-modulated (FM) sweeps into rising and falling on auditory evoked magnetic fields (AEFs) from the human auditory cortex, recorded by means of whole-head magnetoencephalography. AEFs in this task condition were compared with those in a passive condition where subjects had been asked to just passively listen to the same stimulus material. We found that the M100-peak latency was significantly shorter for the task condition than for the passive condition in the left but not in the right hemisphere. Furthermore, the M100-peak latency was significantly shorter in the right than in the left hemisphere for the passive and the task conditions. In contrast, the M100-peak amplitude did not differ significantly between conditions, nor between hemispheres. We also analyzed the activation strength derived from the integral of the absolute magnetic field over constant time windows between stimulus onset and 260 ms. We isolated an early, narrow time range between about 60 ms and 80 ms that showed larger values in the task condition, most prominently in the right hemisphere. These results add to other imaging and lesion studies which suggest a specific role of the right auditory cortex in identifying FM sweep direction and thus in categorizing FM sweeps into rising and falling.

Neural interactions within and beyond the critical band elicited by two simultaneously presented narrow band noises: a magnetoencephalographic study.

Neural activities elicited in the auditory system are systematically organized according to the frequency characteristics of corresponding sound inputs. This systematic frequency alignment, called 'tonotopy,' plays an important role in auditory perception. By means of magnetoencephalography (MEG) we investigated here interactions between neural groups activated by two simultaneously presented narrow-band noises (NBNs) within the human cortical tonotopic map. Auditory evoked fields indicated that the neural interactions activated by these NBNs depended on the frequency difference between them: the amplitude of the N1m-response systematically increased with increasing frequency difference between the NBNs until the critical bandwidth was reached. In contrast, the N1m decreased with frequency difference exceeding the critical bandwidth. The different N1m-response patterns within and beyond the critical band seem to result from the combination of inhibitory and excitatory neural processes in the auditory pathway and may contribute to the perception of complex sound patterns like speech and music.

Neuromagnetic responses to chords are modified by preceding musical scale.

Previous psychological studies have shown that musical chords primed by Western musical scale in a tonal and modal schema are perceived in a hierarchy of stability. We investigated such priming effects on auditory magnetic responses to tonic-major and submediant-minor chords preceded by major scales and tonic-minor and submediant-major chords preceded by minor scales. Musically trained subjects participated in the experiment. During MEG recordings, subjects judged perceptual stability of the chords. The tonic chords were judged to be stable, whereas the submediant chords were judged to be unstable. Dipole moments of N1m response originating in the auditory cortex were larger in the left hemisphere for the submediant chords than for the tonic chords preceded by the major but not minor scales. No difference in the N1m or P2m moment was found for the chords presented without preceding scales. These results suggest priming effects of the tonal schema, interacting with contextual modality, on neural activity of the auditory cortex as well as perceptual stability of the chords. It is inferred that modulation of the auditory cortical activity is associated with attention induced by tonal instability and modality shift, which characterize the submediant chords.

Effects of GSM cellular phones on human hearing: the European project "GUARD".

The European multicenter project named GUARD involved nine centers and aimed to assess potential changes in auditory function as a consequence of exposure to low-intensity electromagnetic fields (EMFs) produced by GSM cellular phones. Participants were healthy young adults without any evidence of hearing or ear disorders. Auditory function was assessed immediately before and after exposure to EMFs, and only the exposed ear was tested. The procedure was conducted twice in a double blinded design, once with a genuine EMF exposure and once with a sham exposure (at least 24 h apart). Tests for assessment of auditory function were hearing threshold level (HTL), transient otoacoustic emissions (TEOAE), distortion product otoacoustic emissions (DPOAE), and auditory brainstem response (ABR). The exposure consisted of speech at a typical conversational level delivered via an earphone to one ear, plus genuine or sham EMF exposure. The EMF exposure used the output of a software-controlled consumer cellular phone at full power for 10 min. A system of phone positioning that allowed participants to freely move their heads without affecting exposure was used. Analysis of the data showed there were no effects of exposure to GSM mobile phone signals on the main measures of the status of the auditory system.

Transcranial magnetic stimulation for the treatment of tinnitus: effects on cortical excitability.

BACKGROUND: Low frequency repetitive transcranial magnetic stimulation (rTMS) has been proposed as an innovative treatment for chronic tinnitus. The aim of the present study was to elucidate the underlying mechanism and to evaluate the relationship between clinical outcome and changes in cortical excitability. We investigated ten patients with chronic tinnitus who participated in a sham-controlled crossover treatment trial. Magnetic-resonance-imaging and positron-emission-tomography guided 1 Hz rTMS were performed over the auditory cortex on 5 consecutive days. Active and sham treatments were separated by one week. Parameters of cortical excitability (motor thresholds, intracortical inhibition, intracortical facilitation, cortical silent period) were measured serially before and after rTMS treatment by using single- and paired-pulse transcranial magnetic stimulation. Clinical improvement was assessed with a standardized tinnitus-questionnaire. RESULTS: We noted a significant interaction between treatment response and changes in motor cortex excitability during active rTMS. Specifically, clinical improvement was associated with an increase in intracortical inhibition, intracortical facilitation and a prolongation of the cortical silent period. These results indicate that intraindividual changes in cortical excitability may serve as a correlate of response to rTMS treatment. CONCLUSION: The observed alterations of cortical excitability suggest that low frequency rTMS may evoke long-term-depression like effects resulting in an improvement of subcortical inhibitory function.

Hearing of microwave pulses by humans and animals: effects, mechanism, and thresholds.

The hearing of microwave pulses is a unique exception to the airborne or bone-conducted sound energy normally encountered in human auditory perception. The hearing apparatus commonly responds to airborne or bone-conducted acoustic or sound pressure waves in the audible frequency range. But the hearing of microwave pulses involves electromagnetic waves whose frequency ranges from hundreds of MHz to tens of GHz. Since electromagnetic waves (e.g., light) are seen but not heard, the report of auditory perception of microwave pulses was at once astonishing and intriguing. Moreover, it stood in sharp contrast to the responses associated with continuous-wave microwave radiation. Experimental and theoretical studies have shown that the microwave auditory phenomenon does not arise from an interaction of microwave pulses directly with the auditory nerves or neurons along the auditory neurophysiological pathways of the central nervous system. Instead, the microwave pulse, upon absorption by soft tissues in the head, launches a thermoelastic wave of acoustic pressure that travels by bone conduction to the inner ear. There, it activates the cochlear receptors via the same process involved for normal hearing. Aside from tissue heating, microwave auditory effect is the most widely accepted biological effect of microwave radiation with a known mechanism of interaction: the thermoelastic theory. The phenomenon, mechanism, power requirement, pressure amplitude, and auditory thresholds of microwave hearing are discussed in this paper. A specific emphasis is placed on human exposures to wireless communication fields and magnetic resonance imaging (MRI) coils.

Exposure setup to study potential adverse effects at GSM 1800 and UMTS frequencies on the auditory systems of rats.

To investigate possible biological effects of exposure to electromagnetic (EM) fields at the frequencies of global system for mobile communication (GSM) 1800 system and universal mobile telecommunication system (UMTS) on the auditory system of rats, an exposure setup for in vivo experiments is presented. The study was carried out in the framework of two European research projects. The target of the investigation was the cochlea. A dosimetric study was performed, both numerically and through direct measurements, to assess the interaction of the radiated fields and the dose distribution in the biological target. For the local exposure of rats, a loop antenna operating at the frequency bands of interest was designed, realised and characterised through numerical and experimental dosimetric procedures. Moreover, an exposure apparatus was set up, consisting of three arrays of four loop antennas, placed on three levels, thus allowing simultaneous exposure of 12 rats to give statistical power to the experiments. To isolate the exposure arrays, the setup was assembled by a wooden rack with EM field absorbing panels, inserted among the levels and at the four sides of the rack. Isolation was verified by direct measurements. Two exposure arrays were simultaneously supplied, whereas the third one was used for sham exposure. Blind exposure was achieved through a black box, hiding physical connections to the microwave power supply. During exposure sessions, rats were restrained in special plastic jigs for repeatable positioning, thus assuring the fixed level of dose in the target.

Auditory response characteristics of the piebald odorous frog and their implications.

The piebald odorous frog (Odorrana schmackeri), the large odorous frog (Odorrana livida) and the concave-eared torrent frog (Amolops tormotus) are sympatric species living near the same torrent streams in the vicinity of Mt. Huangshan, China. A recent study demonstrated that A. tormotus can use sound signals involving ultrasonic components for communication in a noisy environment, and another sympatric species, O. livida, can also perceive ultrasonic sound. Here we report data on the hearing range of O. schmackeri by studying auditory evoked potentials and single-unit data from the torus semicircularis. This frog exhibits its two most sensitive peaks at 2 kHz and 3.5-4.0 kHz with thresholds <42 dB SPL, with an upper frequency limit of hearing at 8.5 kHz with threshold of 87 dB SPL. The upper limit is much lower than those of O. livida and A. tormotus, at 22 and 34 kHz, respectively. It suggests that sympatric species may respond differently to similar environmental selection pressures sculpting auditory communication systems.

The role of biological system other than auditory air-conduction in the emergence of the hypersonic effect.

Although human beings cannot perceive elastic vibrations in the frequency range above 20 kHz, nonstationary sounds containing a wealth of inaudible high-frequency components (HFC) above the human audible range activate deep-lying brain structures, including the brainstem and thalamus and evoke various physiological, psychological, and behavioral responses. In the previous reports, we have called these phenomena collectively "the hypersonic effect." It remains unclear, however, if vibratory stimuli above the audible range are transduced and perceived solely via the conventional air-conducting auditory system or if other mechanisms also contribute to mediate transduction and perception. In the present study, we have examined the emergence of the hypersonic effect when inaudible HFC and audible low-frequency components (LFC) were presented selectively to the ears, the entrance of an air-conducting auditory system, or to the body surface including the head which might contain some unknown vibratory sensing mechanisms. We used two independent measurements based on differing principles; one physiological (alpha 2 frequency of spontaneous electroencephalogram [alpha-EEG]) and the other behavioral (the comfortable listening level [CLL]). Only when the listener's entire body surface was exposed to HFC, but not when HFC was presented exclusively to the air-conducting auditory system, did both the alpha-EEG and the CLL significantly increase compared to the presentation of LFC alone, that is to say, there was an evident emergence of the hypersonic effect. The present findings suggest that the conventional air-conducting auditory system alone does not bring about the hypersonic effect. We may need to consider the possible involvement of a biological system distinct from the conventional air-conducting auditory nervous system in sensing and transducing high-frequency elastic vibration above the human audible range.