ABSTRACT
OBJECTIVE: Repetitive transcranial magnetic stimulation (rTMS) is a potential therapeutic tool to rehabilitate chronic stroke patients. In this study, the safety of high-frequency rTMS in stroke was investigated (Phase I). METHODS: The safety of 20 and 25 Hz rTMS over the motor cortex (MC) of the affected hemisphere, with intensities of 110-130% of the motor threshold (MT), was evaluated using surface electromyography (EMG) of hand and arm muscles. RESULTS: Brief EMG bursts, possibly representing peripheral manifestations of after discharges, and spread of excitation to proximal muscles are considered to be associated with a high risk of seizure occurrence. These events were recorded after the rTMS trains. Neither increased MC excitability nor improved pinch force dynamometry was found after rTMS. CONCLUSIONS: Stimulation parameters for rTMS, which are safe for healthy volunteers, may lead to a higher risk for seizure occurrence in chronic stroke patients. SIGNIFICANCE: rTMS at rates of 20 and 25 Hz using above threshold stimulation potentially increases the risk of seizures in patients with chronic stroke.
Subject(s)
Stroke Rehabilitation , Transcranial Magnetic Stimulation/adverse effects , Adult , Aged , Arm , Chronic Disease , Electromyography , Evoked Potentials, Motor , Female , Hand , Humans , Male , Middle Aged , Motor Cortex/physiopathology , Muscle Strength Dynamometer , Muscle, Skeletal/physiopathology , Risk Assessment , Seizures/etiology , Stroke/physiopathologyABSTRACT
BACKGROUND: Data from the human motor cortex suggest that, depending on polarity, direct current (DC) brain polarization can depress or activate cortical neurons. Activating effects on the frontal lobe might be beneficial for patients with frontal lobe disorders. This phase 1 study tested the safety of frontal DC, including its effects on frontal and other brain functions. METHODS: The authors applied 20 minutes of anodal, cathodal, or sham DC to the left prefrontal cortex in three groups of right-handed subjects and looked for effects on global measures of processing and psychomotor speed, emotion, and verbal fluency, a measure of local cortical function. In one experiment (n = 30), the authors tested before and after 1 mA DC and monitored EEG in 9 subjects. In two other experiments using 1 mA (n = 43) and 2 mA (n = 30), the authors tested before and then starting 5 minutes after the onset of DC. RESULTS: All subjects tolerated DC well. There were no significant effects on performance with 1 mA DC. At 2 mA, verbal fluency improved significantly with anodal and decreased mildly with cathodal DC. There were no clinically significant effects on the other measures. CONCLUSIONS: Limited exposure to direct current polarization of the prefrontal cortex is safe and can enhance verbal fluency selectively in healthy subjects. As such, it deserves consideration as a procedure to improve frontal lobe function in patients.
Subject(s)
Cognition/physiology , Electric Stimulation Therapy/adverse effects , Electric Stimulation Therapy/methods , Mental Disorders/therapy , Prefrontal Cortex/physiology , Adult , Aged , Electrodes , Electroencephalography , Female , Humans , Language Tests , Male , Mental Disorders/physiopathology , Middle Aged , Neuropsychological Tests , Prefrontal Cortex/physiopathology , Reference Values , Verbal Behavior/physiologyABSTRACT
Previous studies using BOLD fMRI to examine age-related changes in cortical activation used tasks that relied on peripheral systems to activate the brain. They were unable to distinguish between alterations due to age-related changes in the periphery and actual changes in cortical physiology. Transcranial magnetic stimulation (TMS), which allows direct, noninvasive stimulation of cortical neurons, was interleaved with BOLD fMRI to study 6 young and 5 old subjects. Three different tasks were compared: direct stimulation by TMS, indirect active stimulation produced by a motor task, and indirect passive stimulation produced by hearing the TMS coil discharge. Direct neuronal stimulation by TMS produced similar fMRI signal increases in both groups, suggesting that cortical physiology itself may not necessarily decline with age.
Subject(s)
Aging/physiology , Cerebral Cortex/physiology , Electric Stimulation , Electromagnetic Fields , Magnetic Resonance Imaging , Acoustic Stimulation , Adult , Aged , Female , Humans , Male , Middle Aged , Motor Activity/physiology , Motor Cortex/physiologyABSTRACT
Over the past 5 years, and especially within the last year, there has been a rapid expansion of vagus nerve stimulation (VNS)-related preclinical research, as well as clinical studies in indications other than epilepsy. The research advances in understanding VNS are occurring in the midst of a blossoming of other forms of therapeutic brain stimulation, such as electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), and deep brain stimulation (DBS). In general, improved understanding of the neurobiological effects of VNS therapy as a function of the different use parameters (frequency, intensity, pulse width, duration, dose) is beginning to guide clinical use and help determine which diseases, in addition to epilepsy, VNS might treat.
Subject(s)
Depression/therapy , Electric Stimulation Therapy , Epilepsy/therapy , Vagus Nerve/physiology , Anxiety/therapy , Humans , Obesity/therapy , Pain ManagementABSTRACT
Transcranial magnetic stimulation (TMS) administered over the prefrontal cortex has been shown to subtly influence neuropsychological tasks, and has antidepressant effects when applied daily for several weeks. Prefrontal TMS does not, however, produce an immediate easily observable effect, making it hard to determine if one has stimulated the cortex. Most prefrontal TMS studies have stimulated using intensity relative to the more easily determined motor threshold (MT) over motor cortex. Five healthy adults were studied in a 1.5 T MRI scanner during short trains of 1 Hz TMS delivered with a figure eight MR compatible TMS coil followed by rest epochs. In a randomized manner, left prefrontal TMS was delivered at 80%, 100% and 120% of MT interleaved with BOLD fMRI acquisition. Compared to rest, all TMS epochs activated auditory cortex, with 80% MT having no other areas of significant activation. 100% MT showed contralateral activation and 120% MT showed bilateral prefrontal activation. Higher intensity TMS, compared to lower, in general produced more activity both under the coil and contralaterally. Higher prefrontal TMS stimulation intensity produces greater local and contralateral activation. Importantly, unilateral prefrontal TMS produces bilateral effects, and TMS at 80% MT produces only minimal prefrontal cortex activation.
Subject(s)
Functional Laterality/physiology , Magnetic Resonance Imaging , Prefrontal Cortex/anatomy & histology , Prefrontal Cortex/physiology , Transcranial Magnetic Stimulation , Adult , Auditory Cortex/physiology , Brain Mapping , Feasibility Studies , Female , Humans , Male , Oxygen/blood , Physical StimulationABSTRACT
RATIONALE AND OBJECTIVES: Left cervical vagus nerve stimulation (VNS) by use of an implanted neurocybernetic prosthesis (NCP) system is effective in treating epilepsy, with open data suggesting effectiveness in depression, yet the mechanisms of action are unknown. Our objective was to develop a methodology for performing VNS-synchronized functional magnetic resonance imaging (VNS-fMRI) and then to demonstrate its feasibility for studying VNS effects. METHODS: In nine patients implanted for treatment of intractable depression, a Macintosh computer was used to detect the signal from the implanted VNS stimulator and then to synchronize fMRI image acquisition with its regular firing. RESULTS: With our VNS-fMRI methodology, the blood oxygenation level-dependent response to VNS was shown in brain regions regulated by the vagus nerve: orbitofrontal and parieto-occipital cortex bilaterally, left temporal cortex, the hypothalamus, and the left amygdala. CONCLUSIONS: Vagus nerve stimulation pulses from an NCP system can be detected externally to determine its firing pattern, thus allowing VNS-fMRI studies of VNS-induced brain activity.
Subject(s)
Brain Mapping/methods , Depression/physiopathology , Depression/therapy , Electric Stimulation/methods , Magnetic Resonance Imaging/methods , Vagus Nerve/physiology , Adult , Electrodes , Feasibility Studies , Female , Humans , Image Processing, Computer-Assisted , Male , Middle Aged , Oxygen/blood , Pilot ProjectsABSTRACT
We built a low-cost system for monitoring human skin conductance responses (SCRs) in a clinical magnetic resonance (MR) scanner during functional imaging. The average scanner-induced conductance noise level was suppressed sufficiently to allow SCR measurements over the full range of SCR amplitudes, and functional image signal-to-noise ratio was unaffected by the skin conductance apparatus. The system may be useful for a variety of imaging studies.
Subject(s)
Galvanic Skin Response , Magnetic Resonance Imaging , Humans , Magnetic Resonance Imaging/instrumentation , Monitoring, Physiologic/instrumentationABSTRACT
Five healthy volunteers were studied using interleaved transcranial magnetic stimulation/functional magnetic resonance imaging (TMS/fMRI) and an averaged single trial (AST) protocol. Blood oxygenation level-dependent (BOLD)-fMRI response to single TMS pulses over the motor cortex was detectable in both the ipsilateral motor cortex under the TMS coil and the contralateral motor cortex, as well as bilaterally in the auditory cortex. The associated BOLD signal increase showed the typical fMRI hemodynamic response time course. The brain's response to a single TMS pulse over the motor cortex at 120% of the level required to induce thumb movement (1.0%-1.5% signal increase) was comparable in both level and duration to the auditory cortex response to the sound accompanying the TMS pulse (1.5% -2.0% signal increase).
Subject(s)
Electromagnetic Phenomena , Evoked Potentials, Motor/physiology , Magnetic Resonance Imaging/methods , Motor Cortex/physiology , Reaction Time/physiology , Adult , Brain Mapping , Humans , Magnetic Resonance Imaging/instrumentation , Male , Reference Values , Sensitivity and SpecificityABSTRACT
Although the vagus nerve has traditionally been considered to perform efferent functions, in reality it performs significant afferent functions as well, carrying information from the body, head, and neck to the brain. Preliminary studies examining this afferent activity led to the theory that vagus nerve stimulation (VNS) could successfully control seizure activity in persons who are refractory to antiepileptic medications. Unlike other forms of brain stimulation, VNS is unable to directly stimulate multiple discrete areas of the brain; however, through several pathways, it is able to relay sensory information to higher brain regions. An implantable VNS device known as the VNSTM NeuroCybernetic Prosthesis (NCP) System has been used in approximately 9,000 epilepsy patients in Europe and the United States since 1994. The implant has reduced seizure frequency by an average of 25% to 30%, with minimal side effects. Studies underway are also showing some degree of success in the management of treatment-refractory depression. The future efficacy of the implantable system in other disorders may depend on whether the implant can be more precisely focused to affect different brain regions. Research in this area is underway.
ABSTRACT
Transcranial magnetic stimulation (TMS) was applied in combination with psychotherapy in patients with neurotic depression, including 15 patients of the experimental group and 14 patients of the control one. 10 sessions of daily TMS for the patients from the experimental group (0.015 T, 40 pulses per sec) were performed at the same time for 20 min (twice for 10 min with 5-min interval) in a room which excluded any external stimulation. TMS was performed by contact method: 5 cm coil was applied to the left prefrontal area. The control group received the imitation of TMS-procedure stimulation. The improvement of mental state was in 13 patients of experimental group and in 3 of control one. The course of TMS resulted in a significant attenuation of depression by the Hamilton Depression Rating scale (from 22.9 to 8.6) and the Anxiety Inventory (from 39.4 to 26.6), that was significantly higher in comparison with the control. There weren't found any TMS-related changes in blood pressure and pulse rate as well as any pathological EEG symptoms.
