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Thiele C, Rufener KS, Repplinger S, Zaehle T, Ruhnau P. Transcranial temporal interference stimulation (tTIS) influences event-related alpha activity during mental rotation. Psychophysiology 2024; 61:e14651. [PMID: 38997805 DOI: 10.1111/psyp.14651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 05/14/2024] [Accepted: 07/01/2024] [Indexed: 07/14/2024]
Abstract
Non-invasive brain stimulation techniques offer therapeutic potential for neurological and psychiatric disorders. However, current methods are often limited in their stimulation depth. The novel transcranial temporal interference stimulation (tTIS) aims to overcome this limitation by non-invasively targeting deeper brain regions. In this study, we aimed to evaluate the efficacy of tTIS in modulating alpha activity during a mental rotation task. The effects of tTIS were compared with transcranial alternating current stimulation (tACS) and a sham control. Participants were randomly assigned to a tTIS, tACS, or sham group. They performed alternating blocks of resting and mental rotation tasks before, during, and after stimulation. During the stimulation blocks, participants received 20 min of stimulation adjusted to their individual alpha frequency (IAF). We assessed shifts in resting state alpha power, event-related desynchronization (ERD) of alpha activity during mental rotation, as well as resulting improvements in behavioral performance. Our results indicate tTIS and tACS to be effective in modulating cortical alpha activity during mental rotation, leading to an increase in ERD from pre- to poststimulation as well as compared to sham stimulation. However, this increase in ERD was not correlated with enhanced mental rotation performance, and resting state alpha power remained unchanged. Our findings underscore the complex nature of tTIS and tACS efficacy, indicating that stimulation effects are more observable during active cognitive tasks, while their impacts are less pronounced on resting neuronal systems.
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Affiliation(s)
- Carsten Thiele
- Department of Neurology, Otto-von-Guericke-University, University Clinic of Magdeburg, Magdeburg, Germany
- Center for Behavioral Brain Sciences (CBBS), Otto-von-Guericke-Universität Magdeburg, Magdeburg, Germany
| | - Katharina S Rufener
- Center for Behavioral Brain Sciences (CBBS), Otto-von-Guericke-Universität Magdeburg, Magdeburg, Germany
- Department of Psychiatry, Psychotherapy and Psychosomatic Medicine of Childhood and Adolescents, Otto-von-Guericke-University, University Clinic of Magdeburg, Magdeburg, Germany
| | - Stefan Repplinger
- Department of Neurology, Otto-von-Guericke-University, University Clinic of Magdeburg, Magdeburg, Germany
- Center for Behavioral Brain Sciences (CBBS), Otto-von-Guericke-Universität Magdeburg, Magdeburg, Germany
| | - Tino Zaehle
- Department of Neurology, Otto-von-Guericke-University, University Clinic of Magdeburg, Magdeburg, Germany
- Center for Behavioral Brain Sciences (CBBS), Otto-von-Guericke-Universität Magdeburg, Magdeburg, Germany
| | - Philipp Ruhnau
- Center for Behavioral Brain Sciences (CBBS), Otto-von-Guericke-Universität Magdeburg, Magdeburg, Germany
- School of Psychology and Humanities, University of Central Lancashire, Preston, UK
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Karimi N, Amirfattahi R, Zeidaabadi Nezhad A. Neuromodulation effect of temporal interference stimulation based on network computational model. Front Hum Neurosci 2024; 18:1436205. [PMID: 39386280 PMCID: PMC11461302 DOI: 10.3389/fnhum.2024.1436205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2024] [Accepted: 09/09/2024] [Indexed: 10/12/2024] Open
Abstract
Deep brain stimulation (DBS) has long been the conventional method for targeting deep brain structures, but noninvasive alternatives like transcranial Temporal Interference Stimulation (tTIS) are gaining traction. Research has shown that alternating current influences brain oscillations through neural modulation. Understanding how neurons respond to the stimulus envelope, particularly considering tTIS's high-frequency carrier, is vital for elucidating its mechanism of neuronal engagement. This study aims to explore the focal effects of tTIS across varying amplitudes and modulation depths in different brain regions. An excitatory-inhibitory network using the Izhikevich neuron model was employed to investigate responses to tTIS and compare them with transcranial Alternating Current Stimulation (tACS). We utilized a multi-scale model that integrates brain tissue modeling and network computational modeling to gain insights into the neuromodulatory effects of tTIS on the human brain. By analyzing the parametric space, we delved into phase, amplitude, and frequency entrainment to elucidate how tTIS modulates endogenous alpha oscillations. Our findings highlight a significant difference in current intensity requirements between tTIS and tACS, with tTIS requiring notably higher intensity. We observed distinct network entrainment patterns, primarily due to tTIS's high-frequency component, whereas tACS exhibited harmonic entrainment that tTIS lacked. Spatial resolution analysis of tTIS, conducted via computational modeling and brain field distribution at a 13 Hz stimulation frequency, revealed modulation in deep brain areas, with minimal effects on the surface. Notably, we observed increased power within intrinsic and stimulation bands beneath the electrodes, attributed to the high stimulus signal amplitude. Additionally, Phase Locking Value (PLV) showed slight increments in non-deep areas. Our analysis indicates focal stimulation using tTIS, prompting further investigation into the necessity of high amplitudes to significantly affect deep brain regions, which warrants validation through clinical experiments.
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Affiliation(s)
| | - Rassoul Amirfattahi
- Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, Iran
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Mojiri Z, Rouhani E, Akhavan A, Jokar Z, Alaei H. Non-invasive temporal interference brain stimulation reduces preference on morphine-induced conditioned place preference in rats. Sci Rep 2024; 14:21040. [PMID: 39251806 PMCID: PMC11385117 DOI: 10.1038/s41598-024-71841-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 08/31/2024] [Indexed: 09/11/2024] Open
Abstract
Long-term use of opioid drugs such as morphine can induce addiction in the central nervous system through dysregulation of the reward system of the brain. Deep brain stimulation (DBS) is a non-pharmacological technique capable of attenuating behavioral responses associated with opioid drug consumption and possesses the capability to selectively activate and target localized brain regions with a high spatial resolution. However, long-term implantation of electrodes in brain tissue may limit the effectiveness of DBS due to changes in impedance, position, and shape of the tip of the stimulation electrode and the risk of infection of nerve tissue around the implanted electrode. The main objective of the current study is to evaluate the effect of temporal interference (TI) brain stimulation on addictive behaviors of morphine-induced conditioned place preference (CPP) in rats. TI stimulation is a non-invasive technique used transcranially to modulate neural activity within targeted brain regions. It involves applying two high-frequency currents with slightly different frequencies, resulting in interference and targeted stimulation of different brain areas with the desired spatial resolution. The results indicated that TI stimulation with the amplitude ofI 1 = I 2 = 0.5 mA, carrier frequency of 2 kHz, frequency difference of 25 Hz, ON-OFF stimulation frequency of 0.25 Hz, and total duration of 10 min in three consecutive days resulted in a significant reduction of morphine preference in the morphine-stimulation group in comparison with the morphine group (p < 0.001). These findings highlight the potential of TI stimulation as a modulatory intervention in mitigating the addictive properties of morphine and provide valuable insights into the therapeutic implications of this stimulation paradigm for treatment of opioid drugs in human subjects.
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Affiliation(s)
- Zohre Mojiri
- Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran
| | - Ehsan Rouhani
- Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran
| | - Amir Akhavan
- Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran.
| | - Zahra Jokar
- Department of Physiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Hojjatallah Alaei
- Department of Physiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
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Wu CW, Lin BS, Zhang Z, Hsieh TH, Liou JC, Lo WL, Li YT, Chiu SC, Peng CW. Pilot study of using transcranial temporal interfering theta-burst stimulation for modulating motor excitability in rat. J Neuroeng Rehabil 2024; 21:147. [PMID: 39215318 PMCID: PMC11365202 DOI: 10.1186/s12984-024-01451-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 08/19/2024] [Indexed: 09/04/2024] Open
Abstract
Transcranial temporal interference stimulation (tTIS) is a promising brain stimulation method that can target deep brain regions by delivering an interfering current from surface electrodes. Most instances of tTIS stimulate the brain with a single-frequency sinusoidal waveform generated by wave interference. Theta burst stimulation is an effective stimulation scheme that can modulate neuroplasticity by generating long-term potentiation- or depression-like effects. To broaden tTIS application, we developed a theta burst protocol using tTIS technique to modulate neuroplasticity in rats. Two cannula electrodes were unilaterally implanted into the intact skull over the primary motor cortex. Electrical field of temporal interference envelopes generated by tTIS through cannula electrodes were recorded from primary motor cortex. Theta burst schemes were characterized, and motor activation induced by the stimulation was also evaluated simultaneously by observing electromyographic signals from the corresponding brachioradialis muscle. After validating the stimulation scheme, we further tested the modulatory effects of theta burst stimulation delivered by tTIS and by conventional transcranial electrical stimulation on primary motor cortex excitability. Changes in the amplitude of motor evoked potentials, elicited when the primary motor cortex was activated by electrical pulses, were measured before and after theta burst stimulation by both techniques. Significant potentiation and suppression were found at 15 to 30 min after the intermittent and continuous theta burst stimulation delivered using tTIS, respectively. However, comparing to theta burst stimulations delivered using conventional form of transcranial electrical stimulation, using tTIS expressed no significant difference in modulating motor evoked potential amplitudes. Sham treatment from both methods had no effect on changing the motor evoked potential amplitude. The present study demonstrated the feasibility of using tTIS to achieve a theta burst stimulation scheme for motor cortical neuromodulation. These findings also indicated the future potential of using tTIS to carry out theta burst stimulation protocols in deep-brain networks for modulating neuroplasticity.
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Affiliation(s)
- Chun-Wei Wu
- School of Biomedical Engineering, College of Biomedical Engineering, Taipei Medical University, Taipei, 11031, Taiwan
| | - Bor-Shing Lin
- Department of Computer Science and Information Engineering, National Taipei University, New Taipei City 237303, Taiwan
| | - Zhao Zhang
- School of Mechanical and Electrical Engineering, Wuyi University, Wuyishan City, Fujian Province, China
| | - Tsung-Hsun Hsieh
- School of Physical Therapy and Graduate Institute of Rehabilitation Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan
- Neuroscience Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan
| | - Jian-Chiun Liou
- School of Biomedical Engineering, College of Biomedical Engineering, Taipei Medical University, Taipei, 11031, Taiwan
| | - Wei-Lun Lo
- Department of Surgery, Division of Neurosurgery, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan
- Department of Surgery, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Yu-Ting Li
- Taiwan Instrument Research Institute, National Applied Research Laboratories, Hsinchu, Taiwan
| | - Shao-Chu Chiu
- School of Biomedical Engineering, College of Biomedical Engineering, Taipei Medical University, Taipei, 11031, Taiwan
| | - Chih-Wei Peng
- School of Biomedical Engineering, College of Biomedical Engineering, Taipei Medical University, Taipei, 11031, Taiwan.
- School of Gerontology and Long-Term Care, College of Nursing, Taipei Medical University, Taipei, Taiwan.
- Graduate Institute of Biomedical Optomechatronics, College of Biomedical Engineering, Taipei Medical University, Taipei, 11031, Taiwan.
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Ahtiainen A, Leydolph L, Tanskanen JMA, Hunold A, Haueisen J, Hyttinen JAK. Electric field temporal interference stimulation of neurons in vitro. LAB ON A CHIP 2024; 24:3945-3957. [PMID: 38994783 DOI: 10.1039/d4lc00224e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/13/2024]
Abstract
Electrical stimulation (ES) techniques, such as deep brain and transcranial electrical stimulation, have shown promise in alleviating the symptoms of depression and other neurological disorders in vivo. A new noninvasive ES method called temporal interference stimulation (TIS), possesses great potential as it can be used to steer the stimulation and possibly selectively modulate different brain regions. To study TIS in a controlled environment, we successfully established an in vitro 'TIS on a chip' setup using rat cortical neurons on microelectrode arrays (MEAs) in combination with a current stimulator. We validated the developed TIS system and demonstrated the spatial steerability of the stimulation by direct electric field measurements in the chip setup. We stimulated cultures of rat cortical neurons at 28 days in vitro (DIV) by two-channel stimulation delivering 1) TIS at 653 Hz and 643 Hz, resulting in a 10 Hz frequency envelope, 2) low-frequency stimulation (LFS) at 10 Hz and 3) high-frequency stimulation (HFS) at 653 Hz. Unstimulated cultures were used as control/sham. We observed the differences in the electric field strengths during TIS, HFS, and LFS. Moreover, HFS and LFS had the smallest effects on neuronal activity. Instead, TIS elicited neuronal electrophysiological responses, especially 24 hours after stimulation. Our 'TIS on a chip' approach eludicates the applicability of TIS as a method to modulate neuronal electrophysiological activity. The TIS on a chip approach provides spatially steerable stimuli while mitigating the effects of high stimulus fields near the stimulation electrodes. Thus, the approach opens new avenues for stimulation on a chip applications, allowing the study of neuronal responses to gain insights into the potential clinical applications of TIS in treating various brain disorders.
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Affiliation(s)
- Annika Ahtiainen
- Faculty of Medicine and Health Technology, Tampere University, 33520, Tampere, Finland.
| | - Lilly Leydolph
- Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau, 98693, Ilmenau, Germany
| | - Jarno M A Tanskanen
- Faculty of Medicine and Health Technology, Tampere University, 33520, Tampere, Finland.
| | - Alexander Hunold
- Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau, 98693, Ilmenau, Germany
- neuroConn GmbH, 98693, Ilmenau, Germany
| | - Jens Haueisen
- Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau, 98693, Ilmenau, Germany
- Department of Neurology, Jena University Hospital, 07747 Jena, Germany
| | - Jari A K Hyttinen
- Faculty of Medicine and Health Technology, Tampere University, 33520, Tampere, Finland.
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Liu X, Qi S, Hou L, Liu Y, Wang X. Noninvasive Deep Brain Stimulation via Temporal Interference Electric Fields Enhanced Motor Performance of Mice and Its Neuroplasticity Mechanisms. Mol Neurobiol 2024; 61:3314-3329. [PMID: 37987957 DOI: 10.1007/s12035-023-03721-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 10/17/2023] [Indexed: 11/22/2023]
Abstract
A noninvasive deep brain stimulation via temporal interference (TI) electric fields is a novel neuromodulation technology, but few advances about TI stimulation effectiveness and mechanisms have been reported. One hundred twenty-six mice were selected for the experiment by power analysis. In the present study, TI stimulation was proved to stimulate noninvasively primary motor cortex (M1) of mice, and 7-day TI stimulation with an envelope frequency of 20 Hz (∆f =20 Hz), instead of an envelope frequency of 10 Hz (∆f =10 Hz), could obviously improve mice motor performance. The mechanism of action may be related to enhancing the strength of synaptic connections, improving synaptic transmission efficiency, increasing dendritic spine density, promoting neurotransmitter release, and increasing the expression and activity of synapse-related proteins, such as brain-derived neurotrophic factor (BDNF), postsynaptic density protein-95 (PSD-95), and glutamate receptor protein. Furthermore, the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway and its upstream BDNF play an important role in the enhancement of locomotor performance in mice by TI stimulation. To our knowledge, it is the first report about TI stimulation promoting multiple motor performances and describing its mechanisms. TI stimulation might serve as a novel promising approach to enhance motor performance and treat dysfunction in deep brain regions.
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Affiliation(s)
- Xiaodong Liu
- School of Exercise and Health, Shanghai University of Sport, Shanghai, China
| | - Shuo Qi
- School of Exercise and Health, Shanghai University of Sport, Shanghai, China
| | - Lijuan Hou
- College of Physical Education and Sports, Beijing Normal University, Beijing, China
| | - Yu Liu
- School of Exercise and Health, Shanghai University of Sport, Shanghai, China.
| | - Xiaohui Wang
- School of Exercise and Health, Shanghai University of Sport, Shanghai, China.
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Liu R, Zhu G, Wu Z, Gan Y, Zhang J, Liu J, Wang L. Temporal interference stimulation targets deep primate brain. Neuroimage 2024; 291:120581. [PMID: 38508293 DOI: 10.1016/j.neuroimage.2024.120581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Revised: 03/10/2024] [Accepted: 03/17/2024] [Indexed: 03/22/2024] Open
Abstract
Temporal interference (TI) stimulation, a novel non-invasive stimulation strategy, has recently been shown to modulate neural activity in deep brain regions of living mice. Yet, it is uncertain if this method is applicable to larger brains and whether the electric field produced under traditional safety currents can penetrate deep regions as observed in mice. Despite recent model-based simulation studies offering positive evidence at both macro- and micro-scale levels, the absence of electrophysiological data from actual brains hinders comprehensive understanding and potential application of TI. This study aims to directly measure the spatiotemporal properties of the interfered electric field in the rhesus monkey brain and to validate the effects of TI on the human brain. Two monkeys were involved in the measurement, with implantation of several stereo-electroencephalography (SEEG) depth electrodes. TI stimulation was applied to anesthetized monkeys using two pairs of surface electrodes at differing stimulation parameters. Model-based simulations were also conducted and subsequently compared with actual recordings. Additionally, TI stimulation was administered to patients with motor disorders to validate its effects on motor symptoms. Through the integration of computational electric field simulation with empirical measurements, it was determined that the temporally interfering electric fields in the deep central regions are capable of attaining a magnitude sufficient to induce a subthreshold modulation effect on neural signals. Additionally, an improvement in movement disorders was observed as a result of TI stimulation. This study is the first to systematically measure the TI electric field in living non-human primates, offering empirical evidence that TI holds promise as a more focal and precise method for modulating neural activities in deep regions of a large brain. This advancement paves the way for future applications of TI in treating neuropsychiatric disorders.
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Affiliation(s)
- Ruobing Liu
- CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, PR China; Department of Psychology, University of Chinese Academy of Sciences, Beijing, PR China
| | - Guanyu Zhu
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, PR China
| | - Zhengping Wu
- School of Innovations, Sanjiang University, Nanjing, PR China
| | - Yifei Gan
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, PR China
| | - Jianguo Zhang
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, PR China
| | - Jiali Liu
- CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, PR China; Department of Psychology, University of Chinese Academy of Sciences, Beijing, PR China
| | - Liang Wang
- CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, PR China; Department of Psychology, University of Chinese Academy of Sciences, Beijing, PR China.
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Mojiri Z, Akhavan A, Rouhani E, Zahabi SJ. Quantitative analysis of noninvasive deep temporal interference stimulation: A simulation and experimental study. Heliyon 2024; 10:e29482. [PMID: 38655334 PMCID: PMC11035070 DOI: 10.1016/j.heliyon.2024.e29482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Revised: 04/07/2024] [Accepted: 04/08/2024] [Indexed: 04/26/2024] Open
Abstract
Background Deep brain stimulation (DBS) is a method for stimulating deep regions of the brain for the treatment of various neurological and psychiatric disorders such as depression, obsessive-compulsive disorder, addiction, and Parkinson's disease. Generally, DBS can be performed using both invasive and non-invasive approaches. Invasive DBS is associated with several problems, including intracranial bleeding, infection, and changes in the position of the electrode tip. Temporal interference (TI) stimulation is a non-invasive technique used to stimulate deep regions of the brain by applying two high-frequency sinusoidal currents with slightly different frequencies. New method This paper presents insights into the response of the spiking in the Hodgkin-Huxley (HH) neuron model of the rat somatosensory cortex by changing the parameters carrier frequency, current ratio, and difference frequency of TI stimulation. Furthermore, in order to experimentally evaluate the effect of TI stimulation on the activation of the left motor cortex, an experiment was conducted to measure the motion induced by the balanced and unbalanced TI stimulation. In the experiment, a three-axis accelerometer was attached to the right hand of the animal to determine the position of the hand. Results Simulation results of the HH model showed that the frequency of the envelope of the TI stimulation is identical to the fundamental frequency of the neuron spikes. This result was obtained for difference frequencies of 6 Hz and 9 Hz in balanced and unbalanced TI stimulations. Moreover specifically, when the difference frequency is set to zero, the carrier frequency is within the range of 1300-1400 Hz, and the current range is between 140 and 250 μA/cm2, the firing rate reached to its highest value. In the experimental result, the maximum range of movement at a difference frequency of Δf = 6 Hz was approximately 1.6 mm and 5.3 mm in the z and y directions respectively. Comparison with existing method The results of the spatial spectrum of the rat hand movement were consistent with the spectrum information of the simulation results. Additionally, steering the interfering region to the left motor cortex leads to noticeable contralateral movement of the right hand while no movement was observed in the right hand during the stimulation of the right motor cortex. Conclusion This technique of stimulation for the deep regions of the brain is a promising tool to noninvasively treat various neurological and psychiatric disorders such as morphine dependence in addicted rats.
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Affiliation(s)
- Zohre Mojiri
- Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran
| | - Amir Akhavan
- Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran
| | - Ehsan Rouhani
- Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran
| | - Sayed Jalal Zahabi
- Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran
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Qi S, Liu X, Yu J, Liang Z, Liu Y, Wang X. Temporally interfering electric fields brain stimulation in primary motor cortex of mice promotes motor skill through enhancing neuroplasticity. Brain Stimul 2024; 17:245-257. [PMID: 38428583 DOI: 10.1016/j.brs.2024.02.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 02/09/2024] [Accepted: 02/21/2024] [Indexed: 03/03/2024] Open
Abstract
Temporal interference (TI) electric field brain stimulation is a novel neuromodulation technique that enables the non-invasive modulation of deep brain regions, but few advances about TI stimulation effectiveness and mechanisms have been reported. Conventional transcranial alternating current stimulation (tACS) can enhance motor skills, whether TI stimulation has an effect on motor skills in mice has not been elucidated. In the present study, TI stimulation was proved to stimulating noninvasively primary motor cortex (M1) of mice, and that TI stimulation with an envelope wave frequency of 20 Hz (Δ f = 20 Hz) once a day for 20 min for 7 consecutive days significantly improved the motor skills of mice. The mechanism of action may be related to regulating of neurotransmitter metabolism, increasing the expression of synapse-related proteins, promoting neurotransmitter release, increasing dendritic spine density, enhancing the number of synaptic vesicles and the thickness of postsynaptic dense material, and ultimately enhance neuronal excitability and plasticity. It is the first report about TI stimulation promoting motor skills of mice and describing its mechanisms.
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Affiliation(s)
- Shuo Qi
- Key Laboratory of Exercise and Health Sciences of Ministry of Education, Shanghai University of Sport, Shanghai, China; School of Exercise and Health, Shanghai University of Sport, Shanghai, China; School of Sport and Health, Shandong Sport University, Jinan, China
| | - Xiaodong Liu
- Key Laboratory of Exercise and Health Sciences of Ministry of Education, Shanghai University of Sport, Shanghai, China; School of Exercise and Health, Shanghai University of Sport, Shanghai, China
| | - Jinglun Yu
- Key Laboratory of Exercise and Health Sciences of Ministry of Education, Shanghai University of Sport, Shanghai, China; School of Exercise and Health, Shanghai University of Sport, Shanghai, China
| | - Zhiqiang Liang
- Key Laboratory of Exercise and Health Sciences of Ministry of Education, Shanghai University of Sport, Shanghai, China; School of Exercise and Health, Shanghai University of Sport, Shanghai, China
| | - Yu Liu
- Key Laboratory of Exercise and Health Sciences of Ministry of Education, Shanghai University of Sport, Shanghai, China; School of Exercise and Health, Shanghai University of Sport, Shanghai, China.
| | - Xiaohui Wang
- Key Laboratory of Exercise and Health Sciences of Ministry of Education, Shanghai University of Sport, Shanghai, China; School of Exercise and Health, Shanghai University of Sport, Shanghai, China.
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Guo W, He Y, Zhang W, Sun Y, Wang J, Liu S, Ming D. A novel non-invasive brain stimulation technique: "Temporally interfering electrical stimulation". Front Neurosci 2023; 17:1092539. [PMID: 36777641 PMCID: PMC9912300 DOI: 10.3389/fnins.2023.1092539] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 01/17/2023] [Indexed: 01/30/2023] Open
Abstract
For decades, neuromodulation technology has demonstrated tremendous potential in the treatment of neuropsychiatric disorders. However, challenges such as being less intrusive, more concentrated, using less energy, and better public acceptance, must be considered. Several novel and optimized methods are thus urgently desiderated to overcome these barriers. In specific, temporally interfering (TI) electrical stimulation was pioneered in 2017, which used a low-frequency envelope waveform, generated by the superposition of two high-frequency sinusoidal currents of slightly different frequency, to stimulate specific targets inside the brain. TI electrical stimulation holds the advantages of both spatial targeting and non-invasive character. The ability to activate deep pathogenic targets without surgery is intriguing, and it is expected to be employed to treat some neurological or psychiatric disorders. Recently, efforts have been undertaken to investigate the stimulation qualities and translation application of TI electrical stimulation via computational modeling and animal experiments. This review detailed the most recent scientific developments in the field of TI electrical stimulation, with the goal of serving as a reference for future research.
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Affiliation(s)
- Wanting Guo
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Yuchen He
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Wenquan Zhang
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Yiwei Sun
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Junling Wang
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Shuang Liu
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China,*Correspondence: Shuang Liu,
| | - Dong Ming
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China,Department of Biomedical Engineering, College of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin, China,Tianjin International Joint Research Center for Neural Engineering, Tianjin, China,Dong Ming,
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11
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Neuroprotection and Non-Invasive Brain Stimulation: Facts or Fiction? Int J Mol Sci 2022; 23:ijms232213775. [PMID: 36430251 PMCID: PMC9692544 DOI: 10.3390/ijms232213775] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 11/02/2022] [Accepted: 11/05/2022] [Indexed: 11/11/2022] Open
Abstract
Non-Invasive Brain Stimulation (NIBS) techniques, such as transcranial Direct Current Stimulation (tDCS) and repetitive Magnetic Transcranial Stimulation (rTMS), are well-known non-pharmacological approaches to improve both motor and non-motor symptoms in patients with neurodegenerative disorders. Their use is of particular interest especially for the treatment of cognitive impairment in Alzheimer's Disease (AD), as well as axial disturbances in Parkinson's (PD), where conventional pharmacological therapies show very mild and short-lasting effects. However, their ability to interfere with disease progression over time is not well understood; recent evidence suggests that NIBS may have a neuroprotective effect, thus slowing disease progression and modulating the aggregation state of pathological proteins. In this narrative review, we gather current knowledge about neuroprotection and NIBS in neurodegenerative diseases (i.e., PD and AD), just mentioning the few results related to stroke. As further matter of debate, we discuss similarities and differences with Deep Brain Stimulation (DBS)-induced neuroprotective effects, and highlight possible future directions for ongoing clinical studies.
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Safety Evaluation of Employing Temporal Interference Transcranial Alternating Current Stimulation in Human Studies. Brain Sci 2022; 12:brainsci12091194. [PMID: 36138930 PMCID: PMC9496688 DOI: 10.3390/brainsci12091194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 08/31/2022] [Accepted: 09/02/2022] [Indexed: 01/20/2023] Open
Abstract
Temporal interference transcranial alternating current stimulation (TI-tACS) is a new technique of noninvasive brain stimulation. Previous studies have shown the effectiveness of TI-tACS in stimulating brain areas in a selective manner. However, its safety in modulating human brain neurons is still untested. In this study, 38 healthy adults were recruited to undergo a series of neurological and neuropsychological measurements regarding safety concerns before and after active (2 mA, 20/70 Hz, 30 min) or sham (0 mA, 0 Hz, 30 min) TI-tACS. The neurological and neuropsychological measurements included electroencephalography (EEG), serum neuron-specific enolase (NSE), the Montreal Cognitive Assessment (MoCA), the Purdue Pegboard Test (PPT), an abbreviated version of the California Computerized Assessment Package (A-CalCAP), a revised version of the Visual Analog Mood Scale (VAMS-R), a self-assessment scale (SAS), and a questionnaire about adverse effects (AEs). We found no significant difference between the measurements of the active and sham TI-tACS groups. Meanwhile, no serious or intolerable adverse effects were reported or observed in the active stimulation group of 19 participants. These results support that TI-tACS is safe and tolerable in terms of neurological and neuropsychological functions and adverse effects for use in human brain stimulation studies under typical transcranial electric stimulation (TES) conditions (2 mA, 20/70 Hz, 30 min).
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Ma R, Xia X, Zhang W, Lu Z, Wu Q, Cui J, Song H, Fan C, Chen X, Zha R, Wei J, Ji GJ, Wang X, Qiu B, Zhang X. High Gamma and Beta Temporal Interference Stimulation in the Human Motor Cortex Improves Motor Functions. Front Neurosci 2022; 15:800436. [PMID: 35046771 PMCID: PMC8761631 DOI: 10.3389/fnins.2021.800436] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Accepted: 11/29/2021] [Indexed: 12/14/2022] Open
Abstract
Background: Temporal interference (TI) stimulation is a new technique of non-invasive brain stimulation. Envelope-modulated waveforms with two high-frequency carriers can activate neurons in target brain regions without stimulating the overlying cortex, which has been validated in mouse brains. However, whether TI stimulation can work on the human brain has not been elucidated. Objective: To assess the effectiveness of the envelope-modulated waveform of TI stimulation on the human primary motor cortex (M1). Methods: Participants attended three sessions of 30-min TI stimulation during a random reaction time task (RRTT) or a serial reaction time task (SRTT). Motor cortex excitability was measured before and after TI stimulation. Results: In the RRTT experiment, only 70 Hz TI stimulation had a promoting effect on the reaction time (RT) performance and excitability of the motor cortex compared to sham stimulation. Meanwhile, compared with the sham condition, only 20 Hz TI stimulation significantly facilitated motor learning in the SRTT experiment, which was significantly positively correlated with the increase in motor evoked potential. Conclusion: These results indicate that the envelope-modulated waveform of TI stimulation has a significant promoting effect on human motor functions, experimentally suggesting the effectiveness of TI stimulation in humans for the first time and paving the way for further explorations.
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Affiliation(s)
- Ru Ma
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China
| | - Xinzhao Xia
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China
| | - Wei Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China
| | - Zhuo Lu
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China
| | - Qianying Wu
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China.,Division of the Humanities and Social Sciences, California Institute of Technology, Pasadena, CA, United States
| | - Jiangtian Cui
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China.,School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Hongwen Song
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China
| | - Chuan Fan
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China
| | - Xueli Chen
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China
| | - Rujing Zha
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China
| | - Junjie Wei
- Department of Neurology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Gong-Jun Ji
- Department of Neurology, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Xiaoxiao Wang
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China
| | - Bensheng Qiu
- Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China
| | - Xiaochu Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Science and Medicine, Department of Radiology, The First Affiliated Hospital of USTC, School of Life Science, University of Science and Technology of China, Hefei, China.,Centers for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei, China.,Department of Psychology, School of Humanities and Social Science, University of Science and Technology of China, Hefei, China.,Biomedical Sciences and Health Laboratory of Anhui Province, University of Science and Technology of China, Hefei, China
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14
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Wang C, Deng H, Kuang S. Restoring Vision Naturally and Noninvasively. Neurosci Bull 2021; 37:1642-1644. [PMID: 34383235 DOI: 10.1007/s12264-021-00760-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 05/29/2021] [Indexed: 11/26/2022] Open
Affiliation(s)
- Chundi Wang
- Department of Psychology and Research Centre of Aeronautic Psychology and Behavior, Beihang University, Beijing, 100191, China
- Peking University HuiLongGuan Clinical Medical School, Beijing HuiLongGuan Hospital, Beijing, 100096, China
| | - Hu Deng
- Peking University HuiLongGuan Clinical Medical School, Beijing HuiLongGuan Hospital, Beijing, 100096, China.
| | - Shenbing Kuang
- State Key Laboratory of Brain and Cognitive Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, 100101, China.
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Gomez-Tames J, Asai A, Hirata A. Multiscale Computational Model Reveals Nerve Response in a Mouse Model for Temporal Interference Brain Stimulation. Front Neurosci 2021; 15:684465. [PMID: 34276293 PMCID: PMC8277927 DOI: 10.3389/fnins.2021.684465] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 06/08/2021] [Indexed: 12/24/2022] Open
Abstract
There has been a growing interest in the non-invasive stimulation of specific brain tissues, while reducing unintended stimulation in surrounding regions, for the medical treatment of brain disorders. Traditional methods for non-invasive brain stimulation, such as transcranial direct current stimulation (tDCS) or transcranial magnetic stimulation (TMS), can stimulate brain regions, but they also simultaneously stimulate the brain and non-brain regions that lie between the target and the stimulation site of the source. Temporal interference (TI) stimulation has been suggested to selectively stimulate brain regions by superposing two alternating currents with slightly different frequencies injected through electrodes attached to the scalp. Previous studies have reported promising results for TI applied to the motor area in mice, but the mechanisms are yet to be clarified. As computational techniques can help reveal different aspects of TI, in this study, we computationally investigated TI stimulation using a multiscale model that computes the generated interference current pattern effects in a neural cortical model of a mouse head. The results indicated that the threshold increased with the carrier frequency and that the beat frequency did not influence the threshold. It was also found that the intensity ratio between the alternating currents changed the location of the responding nerve, which is in agreement with previous experiments. Moreover, particular characteristics of the envelope were investigated to predict the stimulation region intuitively. It was found that regions with high modulation depth (| maximum| − | minimum| values of the envelope) and low minimum envelope (near zero) corresponded with the activation region obtained via neural computation.
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Affiliation(s)
- Jose Gomez-Tames
- Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology, Nagoya, Japan.,Center of Biomedical Physics and Information Technology, Nagoya Institute of Technology, Nagoya, Japan
| | - Akihiro Asai
- Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology, Nagoya, Japan
| | - Akimasa Hirata
- Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology, Nagoya, Japan.,Center of Biomedical Physics and Information Technology, Nagoya Institute of Technology, Nagoya, Japan
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Wu L, Liu T, Wang J. Improving the Effect of Transcranial Alternating Current Stimulation (tACS): A Systematic Review. Front Hum Neurosci 2021; 15:652393. [PMID: 34163340 PMCID: PMC8215166 DOI: 10.3389/fnhum.2021.652393] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 04/26/2021] [Indexed: 11/15/2022] Open
Abstract
With the development of electrical stimulation technology, traditional transcranial alternating current stimulation (tACS) technology has been found to have the drawback of not targeting a specific area accurately. Studies have shown that optimizing the number and position of electrodes during electrical stimulation has a very good effect on enhancing brain stimulation accuracy. At present, an increasing number of laboratories have begun to optimize tACS. However, there has been no study summarizing the optimization methods of tACS. Determining whether different optimization methods are effective and the optimization approach could provide information that could guide future tACS research. We describe the results of recent research on tACS optimization and integrate the optimization approaches of tACS in recent research. Optimization approaches can be classified into two groups: high-definition electrical stimulation and interference modulation electrical stimulation. The optimization methods can be divided into five categories: high-definition tACS, phase-shifted tACS, amplitude-modulated tACS, the temporally interfering (TI) method, and the intersectional short pulse (ISP) method. Finally, we summarize the latest research on hardware useful for tACS improvement and outline future directions.
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Affiliation(s)
- Linyan Wu
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Institute of Health and Rehabilitation Science, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China.,National Engineering Research Center of Health Care and Medical Devices, Guangzhou, China.,The Key Laboratory of Neuro-informatics & Rehabilitation Engineering of Ministry of Civil Affairs, Xi'an, China
| | - Tian Liu
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Institute of Health and Rehabilitation Science, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China.,National Engineering Research Center of Health Care and Medical Devices, Guangzhou, China.,The Key Laboratory of Neuro-informatics & Rehabilitation Engineering of Ministry of Civil Affairs, Xi'an, China
| | - Jue Wang
- The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Institute of Health and Rehabilitation Science, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, China.,National Engineering Research Center of Health Care and Medical Devices, Guangzhou, China.,The Key Laboratory of Neuro-informatics & Rehabilitation Engineering of Ministry of Civil Affairs, Xi'an, China
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Su X, Guo J, Zhou M, Chen J, Li L, Chen Y, Sui X, Li H, Chai X. Computational Modeling of Spatially Selective Retinal Stimulation With Temporally Interfering Electric Fields. IEEE Trans Neural Syst Rehabil Eng 2021; 29:418-428. [PMID: 33507871 DOI: 10.1109/tnsre.2021.3055203] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Retinal electrical stimulation is a widely utilized method to restore visual function for patients with retinal degenerative diseases. Transcorneal electrical stimulation (TES) represents an effective way to improve the visual function due to its potential neuroprotective effect. However, TES with single electrode fails to spatially and selectively stimulate retinal neurons. Herein, a computational modeling method was proposed to explore the feasibility of spatially selective retinal stimulation via temporally interfering electric fields. An eyeball model with multiple electrodes was constructed to simulate the interferential electric fields with various electrode montages and current ratios. The results demonstrated that the temporal interference (TI) stimulation would gradually generate an increasingly localized high-intensity region on retina as the return electrodes moved towards the posterior of the eyeball and got closer. Additionally, the position of the convergent region could be modulated by regulating the current ratio of different electrode channels. The TI strategy with multisite and steerable stimulation can stimulate local retinal region with certain convergence and a relatively large stimulation range, which would be a feasible approach for the spatially selective retinal neuromodulation.
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Mirzakhalili E, Barra B, Capogrosso M, Lempka SF. Biophysics of Temporal Interference Stimulation. Cell Syst 2020; 11:557-572.e5. [PMID: 33157010 DOI: 10.1016/j.cels.2020.10.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 08/21/2020] [Accepted: 10/06/2020] [Indexed: 02/06/2023]
Abstract
Temporal interference (TI) is a non-invasive neurostimulation technique that utilizes high-frequency external electric fields to stimulate deep neuronal structures without affecting superficial, off-target structures. TI represents a potential breakthrough for treating conditions, such as Parkinson's disease and chronic pain. However, early clinical work on TI stimulation was met with mixed outcomes challenging its fundamental mechanisms and applications. Here, we apply established physics to study the mechanisms of TI with the goal of optimizing it for clinical use. We argue that TI stimulation cannot work via passive membrane filtering, as previously hypothesized. Instead, TI stimulation requires an ion-channel mediated signal rectification process. Unfortunately, this mechanism is also responsible for high-frequency conduction block in off-target tissues, thus challenging clinical applications of TI. In consequence, we propose a set of experimental controls that should be performed in future experiments to refine our understanding and practice of TI stimulation. A record of this paper's transparent peer review process is included in the Supplemental Information.
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Affiliation(s)
- Ehsan Mirzakhalili
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Beatrice Barra
- Department of Neuroscience and Movement Science, University of Fribourg, Fribourg, Switzerland; Rehab and Neural Engineering Labs, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Marco Capogrosso
- Rehab and Neural Engineering Labs, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA.
| | - Scott F Lempka
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA; Department of Anesthesiology, University of Michigan, Ann Arbor, MI 48109, USA.
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