1
|
Orcioni S, Paffi A, Camera F, Apollonio F, Liberti M. Automatic decoding of input sinusoidal signal in a neuron model: High pass homomorphic filtering. Neurocomputing 2018. [DOI: 10.1016/j.neucom.2018.03.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
2
|
Paffi A, Camera F, Lucano E, Apollonio F, Liberti M. Time resolved dosimetry of human brain exposed to low frequency pulsed magnetic fields. Phys Med Biol 2016; 61:4452-65. [PMID: 27223143 DOI: 10.1088/0031-9155/61/12/4452] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
An accurate dosimetry is a key issue to understanding brain stimulation and related interaction mechanisms with neuronal tissues at the basis of the increasing amount of literature revealing the effects on human brain induced by low-level, low frequency pulsed magnetic fields (PMFs). Most literature on brain dosimetry estimates the maximum E field value reached inside the tissue without considering its time pattern or tissue dispersivity. Nevertheless a time-resolved dosimetry, accounting for dispersive tissues behavior, becomes necessary considering that the threshold for an effect onset may vary depending on the pulse waveform and that tissues may filter the applied stimulatory fields altering the predicted stimulatory waveform's size and shape. In this paper a time-resolved dosimetry has been applied on a realistic brain model exposed to the signal presented in Capone et al (2009 J. Neural Transm. 116 257-65), accounting for the broadband dispersivity of brain tissues up to several kHz, to accurately reconstruct electric field and current density waveforms inside different brain tissues. The results obtained by exposing the Duke's brain model to this PMF signal show that the E peak in the brain is considerably underestimated if a simple monochromatic dosimetry is carried out at the pulse repetition frequency of 75 Hz.
Collapse
Affiliation(s)
- Alessandra Paffi
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome, via Eudossiana 18, 00184 Rome, Italy
| | | | | | | | | |
Collapse
|
3
|
Legros A, Modolo J, Brown S, Roberston J, Thomas AW. Effects of a 60 Hz Magnetic Field Exposure Up to 3000 μT on Human Brain Activation as Measured by Functional Magnetic Resonance Imaging. PLoS One 2015. [PMID: 26214312 PMCID: PMC4516358 DOI: 10.1371/journal.pone.0132024] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Several aspects of the human nervous system and associated motor and cognitive processes have been reported to be modulated by extremely low-frequency (ELF, < 300 Hz) time-varying Magnetic Fields (MF). Due do their worldwide prevalence; power-line frequencies (60 Hz in North America) are of particular interest. Despite intense research efforts over the last few decades, the potential effects of 60 Hz MF still need to be elucidated, and the underlying mechanisms to be understood. In this study, we have used functional Magnetic Resonance Imaging (fMRI) to characterize potential changes in functional brain activation following human exposure to a 60 Hz MF through motor and cognitive tasks. First, pilot results acquired in a first set of subjects (N=9) were used to demonstrate the technical feasibility of using fMRI to detect subtle changes in functional brain activation with 60 Hz MF exposure at 1800 μT. Second, a full study involving a larger cohort of subjects tested brain activation during 1) a finger tapping task (N=20), and 2) a mental rotation task (N=21); before and after a one-hour, 60 Hz, 3000 μT MF exposure. The results indicate significant changes in task-induced functional brain activation as a consequence of MF exposure. However, no impact on task performance was found. These results illustrate the potential of using fMRI to identify MF-induced changes in functional brain activation, suggesting that a one-hour 60 Hz, 3000 μT MF exposure can modulate activity in specific brain regions after the end of the exposure period (i.e., residual effects). We discuss the possibility that MF exposure at 60 Hz, 3000 μT may be capable of modulating cortical excitability via a modulation of synaptic plasticity processes.
Collapse
Affiliation(s)
- Alexandre Legros
- Human Threshold Research Group, Lawson Health Research Institute, London, Ontario, Canada
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Department of Medical Imaging, Western University, London, Ontario, Canada
- School of Kinesiology, Western University, London, Ontario, Canada
- * E-mail:
| | - Julien Modolo
- Human Threshold Research Group, Lawson Health Research Institute, London, Ontario, Canada
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Department of Medical Imaging, Western University, London, Ontario, Canada
| | - Samantha Brown
- Human Threshold Research Group, Lawson Health Research Institute, London, Ontario, Canada
| | - John Roberston
- Human Threshold Research Group, Lawson Health Research Institute, London, Ontario, Canada
- Department of Medical Biophysics, Western University, London, Ontario, Canada
| | - Alex W. Thomas
- Human Threshold Research Group, Lawson Health Research Institute, London, Ontario, Canada
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Department of Medical Imaging, Western University, London, Ontario, Canada
| |
Collapse
|
4
|
Paffi A, Camera F, Apollonio F, d'Inzeo G, Liberti M. Restoring the encoding properties of a stochastic neuron model by an exogenous noise. Front Comput Neurosci 2015; 9:42. [PMID: 25999845 PMCID: PMC4422033 DOI: 10.3389/fncom.2015.00042] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Accepted: 03/19/2015] [Indexed: 11/13/2022] Open
Abstract
Here we evaluate the possibility of improving the encoding properties of an impaired neuronal system by superimposing an exogenous noise to an external electric stimulation signal. The approach is based on the use of mathematical neuron models consisting of stochastic HH-like circuit, where the impairment of the endogenous presynaptic inputs is described as a subthreshold injected current and the exogenous stimulation signal is a sinusoidal voltage perturbation across the membrane. Our results indicate that a correlated Gaussian noise, added to the sinusoidal signal can significantly increase the encoding properties of the impaired system, through the Stochastic Resonance (SR) phenomenon. These results suggest that an exogenous noise, suitably tailored, could improve the efficacy of those stimulation techniques used in neuronal systems, where the presynaptic sensory neurons are impaired and have to be artificially bypassed.
Collapse
Affiliation(s)
- Alessandra Paffi
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome Rome, Italy ; Italian Inter-University Center for the Study of Electromagnetic Fields and Biological Systems Genova, Italy
| | - Francesca Camera
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome Rome, Italy ; Italian Inter-University Center for the Study of Electromagnetic Fields and Biological Systems Genova, Italy
| | - Francesca Apollonio
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome Rome, Italy ; Italian Inter-University Center for the Study of Electromagnetic Fields and Biological Systems Genova, Italy
| | - Guglielmo d'Inzeo
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome Rome, Italy ; Italian Inter-University Center for the Study of Electromagnetic Fields and Biological Systems Genova, Italy
| | - Micaela Liberti
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome Rome, Italy ; Italian Inter-University Center for the Study of Electromagnetic Fields and Biological Systems Genova, Italy
| |
Collapse
|
5
|
Modolo J, Thomas AW, Legros A. Possible mechanisms of synaptic plasticity modulation by extremely low-frequency magnetic fields. Electromagn Biol Med 2014; 32:137-44. [PMID: 23675616 DOI: 10.3109/15368378.2013.776341] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Understanding the biological mechanisms by which extremely low-frequency (ELF, < 300 Hz) magnetic fields (MFs) interact with human brain activity is an active field of research. Such knowledge is required by international agencies providing guidelines for general public and workers exposure to ELF MFs (such as ICNIRP, the International Commission on Non-Ionizing Radiation Protection). The identification of these interaction mechanisms is extremely challenging, since the effects of ELF MF exposure need to be monitored and understood at very different spatial (from micrometers to centimeters) and temporal (from milliseconds to minutes) scales. One possibility to overcome these issues is to develop biophysical models, based on the systems of mathematical equations describing the electric or metabolic activity of the brain tissue. Biophysical models of the brain activity offer the possibility to simulate how the brain tissue interacts with ELF MFs, in order to gain new insights into experimental data, and to test novel hypotheses regarding interaction mechanisms. This paper presents novel hypotheses regarding the effects of power line (60 Hz in North America) MFs on human brain activity, with arguments from biophysical models. We suggest a hypothetic chain of events that could bridge MF exposure with detectable effects on human neurophysiology. We also suggest novel directions of research in order to reach a convergence of biophysical models of brain activity and corresponding experimental data to identify interaction mechanisms.
Collapse
Affiliation(s)
- Julien Modolo
- Human Threshold Research Group, Lawson Health Research Institute, London, ON, Canada.
| | | | | |
Collapse
|
6
|
De Geeter N, Crevecoeur G, Dupré L, Van Hecke W, Leemans A. A DTI-based model for TMS using the independent impedance method with frequency-dependent tissue parameters. Phys Med Biol 2012; 57:2169-88. [DOI: 10.1088/0031-9155/57/8/2169] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|