Gabriella Tognola

Magnetic stimulation of the nervous system : Induced electric field in unbounded, semi-infinite, spherical, and cylindrical media

Knowledge of the electric field that is induced in the brain or the limbs is of importance in magnetic stimulation of the nervous system. Here, an analytical model based on the reciprocity theorem is used to compare the induced electric field in unbounded, semi-infinite, spherical, and cylinder-like volume conductors. Typical stimulation coil arrangements are considered, including the double coil and various orientations of the single coil. The results can be used to determine when the influence of the boundaries is negligible enough to allow the use of more simplified geometries.

Transverse-field activation mechanism in magnetic stimulation of peripheral nerves

The activating function of peripheral nerves in magnetic stimulation is thought to be the gradient of the induced electric field component parallel to the nerve. This implies that there are several orientations of the coil that should not excite nerves. We show that these orientations, however, often yield high-amplitude and even supramaximal muscle response, indicating that the model of the activating function has to be modified. We propose that the electric field component perpendicular to the nerve is responsible for these unexpected muscle responses. Our conclusion is based on practical experiments with different coils and on computer simulations of the induced electric field and its gradient.

Influence on the mechanisms of generation of distortion product otoacoustic emissions of mobile phone exposure

Mobile phones have become very commonly used throughout the world within a short period of time. Although there is no clear evidence to show harmful physiological effects of electromagnetic fields (EMF) at the levels used by mobile phones, there is widespread public concern that there may be potential for harm. Because mobile phones are usually held close to the ear, it is appropriate to study effects on hearing. In this study, the outer hair cell function of 15 subjects was assessed by DPOAE recording before and after a controlled EMF exposure. To increase the sensitivity of DPOAE recording to identify even small changes in hearing function, an inverse fast Fourier transform (IFFT) analysis and time-domain windowing was applied to separate the two generation mechanisms of DPOAE, the so-called place-fixed and wave-fixed mechanisms, in order to verify if EMF can affects the two DPOAE emission mechanisms. Statistical analysis of the data showed that 10 min of EMF exposure at the maximum power (2 W at 900 MHz or 1 W at 1800 MHz) does not induce any changes in either DPOAE generation mechanism.

‘Derived Nonlinear’ versus ‘Linear’ Click-evoked Otoacoustic Emissions

Recordings of emission evoked in response to transient stimuli (TEOAE) are partially contaminated by the initial stimulus artifact. For this reason, a nonlinear estimation method is widely used (derived nonlinear response, DNLR). The aims of this paper are: (1) to analyse some very basic properties of the derived nonlinear emissions such as the short-time input/output relationships; and (2) to show similarities and differences between the classical averaging (linear) and the derived nonlinear recording techniques, in the same ears, both in time and in the frequency domain. At latencies greater than about 6 ms, responses which are recorded using the derived nonlinear technique exhibit no additional features in comparison with linear recordings, at all stimulus levels. At latencies less than 6 ms, the derived nonlinear technique greatly reduces the linear content of the acoustic artifact, and the response may be considered as the initial part of the emission. However, the derived nonlinear responses tend to be considerably noisier than the linear emissions, thus reducing the effectiveness of the technique. The linear responses show a strikingly similar frequency content with respect to the derived nonlinear responses, at least at a high stimulus level and around the main peaks of the spectrum.

Open ear hearing aids in tinnitus therapy: An efficacy comparison with sound generators

Abstract Objective: This study aimed to compare the effectiveness of tinnitus retraining therapy (TRT) with sound generators or with open ear hearing aids in the rehabilitation of tinnitus for a group of subjects who, according to Jastreboff categories, can be treated with both approaches to sound therapy (borderline of Category 1 and 2). Design: This study was a prospective data collection with a parallel-group design which entailed that each subject was randomly assigned to one of the two treatments group: half of the subjects were fitted binaurally with sound generators, and the other half with open ear hearing aids. Both groups received the same educational counselling sessions. Study sample: Ninety-one subjects passed the screening criteria and were enrolled into the study. Structured interviews, with a variety of measures evaluated through the use of visual-analog scales and the tinnitus handicap inventory self-administered questionnaire, were performed before the therapy and at 3, 6, and 12 months during the therapy. Results: Data showed a highly significant improvement in both tinnitus treatments starting from the first three months and up to one year of therapy, with a progressive and statistically significant decrease in the disability every three months. Conclusions: TRT was equally effective with sound generator or open ear hearing aids: they gave basically identical, statistically indistinguishable results. Sumario Objetivo: El objetivo de este estudio es comparar la efectividad de la terapia de re-entrenamiento del acúfeno (TRT), con generadores del sonido o con auxiliares auditivos con molde abierto en la rehabilitación del acúfeno, para un grupo de sujetos que, de acuerdo con las categorías de Jastreboff, pueden ser tratados con ambos enfoques hacia la terapia del sonido (límite entre la categoría 1 y la 2). Diseño: Este estudio fue una colección prospectiva de datos con un diseño de grupos paralelos en el que cada sujeto fue asignado al azar en uno de los dos grupos de tratamiento: la mitad de los sujetos fueron adaptados binauralmente con generadores de sonido y la otra mitad con auxiliares auditivos con molde abierto. Ambos grupos recibieron las mismas sesiones de asesoría. Muestra: 91 sujetos aprobaron el tamiz de criterios y fueron incluidos en el estudio. Se realizó una entrevista estructurada con una variedad de mediciones evaluadas en la Escala Visual Análoga y el Inventario del Impedimento por el Acúfeno, un cuestionario auto-administrado, antes de la terapia y a los 3, 6 y 12 meses durante la terapia. Resultados: Los datos mostraron una mejoría altamente significativa en ambos tratamientos desde los primeros tres meses y hasta el primer año de terapia con una significancia estadística progresiva y un descenso trimestral significativo en la discapacidad. Conclusiones: La TRT fue igualmente efectiva con generadores de sonido que con auxiliares auditivos de molde abierto: básicamente dieron resultados idénticos, estadísticamente indistinguibles.

Effects of mobile phone exposure on time frequency fine structure of transiently evoked otoacoustic emissions

Mobile phones have become very commonly used worldwide within a short period of time. To date there is only limited knowledge about interaction between electromagnetic fields (EMFs) emitted by mobile phones and the auditory function. Moreover, there is widespread concern that there may be potential for harm. The aim of this study was to assess potential subtle changes in cochlear function by measuring the temporal and spectral fine structure of transiently evoked otoacoustic emissions (TEOAE) in normal hearing subjects after exposure to EMFs emitted by Global System for Mobile Communication (GSM) mobile phones. TEOAEs were recorded in 27 healthy young adults before and after 10 min of real or sham exposure in a double-blind design. TEOAE data were analyzed both globally (broadband analysis) and using the Wavelet Transform (analysis of the time-frequency fine structure). The broadband analysis revealed no significant effect on TEOAEs related to exposure, confirming results of previous studies; in addition, no significant change was detected in the analysis of the elementary wavelet components, suggesting that the temporal and spectral fine structure of TEOAEs is not affected by 10 min exposure to low-intensity EMFs emitted by GSM mobile phones.

Electromagnetic Fields from Mobile Phones do not Affect the Inner Auditory System of Sprague-Dawley Rats

Abstract Galloni, P., Parazzini, M., Piscitelli, M., Pinto, R., Lovisolo, G. A., Tognola, G., Marino, C. and Ravazzani, P. Electromagnetic Fields from Mobile Phones do not Affect the Inner Auditory System of Sprague-Dawley Rats. Radiat. Res. 164, 798–804 (2005). The auditory system is the first biological structure facing the electromagnetic fields emitted by mobile phones. The aim of this study was to evaluate the cochlear functionality of Sprague-Dawley rats exposed to electromagnetic fields at the typical frequencies of GSM mobile phones (900 and 1800 MHz) by distortion product otoacoustic emissions, which are a well-known indicator of the status of the cochleas outer hair cells. A population of 48 rats was divided into exposed and sham-exposed groups. Three sets of four loop antennas, one for sham-exposed animals and two for exposed animals, were used for the local exposures. Rats were exposed 2 h/day, 5 days/week for 4 weeks at a local SAR of 2 W/kg in the ear. Distortion product otoacoustic emissions tests were carried out before, during and after the exposure. The analysis of the data shows no statistically significant differences between the audiological signals recorded for the different groups.

Effects of GSM Cellular Phones on Human Hearing: The European Project “GUARD”

Abstract Parazzini, M., Brazzale, A. R., Paglialonga, A., Tognola, G., Collet, L., Moulin, A., Lutman, M. E., Bell, S. L., Thomas, N. A., Uloziene, I., Uloza, V., Thuroczy, G., Tavartkiladze, G., Tsalighopoulos, M., Kyriafinis, G. and Ravazzani, P. Effects of GSM Cellular Phones on Human Hearing: The European Project “GUARD”. Radiat. Res. 168, 608–613 (2007). 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.

Quantitative analysis of cochlear active mechanisms in tinnitus subjects with normal hearing sensitivity: Time-frequency analysis of transient evoked otoacoustic emissions and contralateral suppression.

OBJECTIVE The aim of this study was to analyze the fine structure of transient evoked otoacoustic emissions (TEOAEs) and contralateral suppression effects in tinnitus subjects with normal hearing in order to assess whether a minor cochlear or efferent dysfunction, possibly limited in narrow cochlear regions, might play a role in tinnitus. METHODS TEOAEs were recorded, both in the absence and in the presence of contralateral acoustic stimulation, in 23 tinnitus patients with normal hearing sensitivity and in 31 non-tinnitus control subjects. The broad-band TEOAE recordings were analyzed by using an innovative algorithm and separated into a set of 33 narrow-band frequency components, that represent the different cochlear contributions to the whole TEOAE response. In each frequency component, three different parameters were analyzed and compared between tinnitus and non-tinnitus subjects, i.e., reproducibility, latency, and the suppression effects induced by contralateral acoustic stimulation. RESULTS Significantly lower reproducibility was observed in the frequency components of the tinnitus subjects compared to the controls, whereas no significant differences in latency and in suppression effects were observed between tinnitus and non-tinnitus ears. CONCLUSIONS The analysis of the fine structure of TEOAEs revealed that the tinnitus subjects involved in this study might, possibly, have a minor dysfunction of the cochlear active mechanisms that resulted in frequency components with lower reproducibility. Conversely, the analysis of suppression effects in the narrow-band frequency components of TEOAE indicated that the subjects involved showed no relevant damage to the efferent regulatory mechanisms that control the cochlear activity, neither through the cochlea as a whole, nor in limited cochlear regions.

The Milan Project: A newborn hearing screening programme: Newborn hearing screening programme

Aim: Since 1997 a newborn hearing screening programme has been implemented by the U.O. Neurologia‐Neurofisiopatologia and Dipartimento di Neonatologia of the Istituti Clinici di Perfezionamento ICP in Milan for both babies with no risk and those at risk of hearing impairment. This programme was named the Milan Project. Methods: The protocol for no‐risk babies consisted of three stages: in the first two stages, newborns were tested with transient click‐evoked otoacoustic emissions (TEOAE), in the third one with conventional auditory brainstem responses (ABR). The first TEOAE test was performed by 36 h of age, before discharge, the second one after 15–30 d in case of referral, and the third one, by ABR, for those babies who failed the second TEOAE stage. Newborns at audiological risk were submitted to conventional ABR before the third month of corrected age. Some of this latter population was also submitted to the TEOAE test. The entire tested population (no‐risk babies and newborns at audiological risk) consisted of 19 777 babies: 19 290 without risk (“no risk”) and 487 at risk (“at risk”). Results: During the course of the Milan Project, hearing impairment (ABR threshold equal to or greater than 40 dB nHL) was identified in 63 newborns (19 from the no‐risk and 44 from the at‐risk population), with a prevalence of 0.32%. Bilateral hearing impairment (BHI) was found in 33 newborns (10 from the no‐risk and 23 from the at‐risk population), corresponding to 0.17%. Among infants with bilateral hearing impairment, 30.3% had no risk factors. The prevalence of hearing impairment was determined on days 15–30 after birth.