Brain Stimulation

Wednesday, 06 de November de 2019

              

 
  Brain stimulation involves techniques that modulate brain activity through physical agents such as electric current or electromagnetic induction in order to treat some neurological pathology or restore the central nervous system. The techniques can be invasive like DBS (Deep Brain Stimulation) or non-invasive like TMS (Transcranial Magnetic Stimulation) or tDCS (transcranial Direct Current Stimulation)

   
 DBS (Blackrock microsystems) is the stimulation method that involves surgery to microelectrode implant a device that sends electrical signals to brain areas responsible for body movement. Electrodes are placed deep in the brain and are connected to a stimulator device. Similar to a heart pacemaker, a neurostimulator uses electric pulses to regulate brain activity. Depending on the type of parameters used, such as wavelength, amplitude, frequency, and type of current, for example, it is possible to stimulate or inhibit specific areas of the brain. As we saw in our blog " Intracerebral microelectrode implantation: present, future, and challenges.", DBS can be used in patients with Parkinson's disease, where dopaminergic neurons die in the region known as the nigrostriatal pathway, causing a disorder in the passage of signal from the motor cortex to the rest of the CNS, causing the patient has motor deficits, such as rest tremor and difficulty in walking. However, with deep brain stimulation (Micro brain electrode implantation), the patient has a significant improvement in these signs and symptoms (Video below). In addition to microelectrode implantation, this method also includes the implantation of a generator responsible for providing electrical stimulation. Also, Electrostimulation can also be used to induce brain injury in animal models to simulate some kind of disease. For this, the current parameters are changed to harmful cellular parameters.

      

 TMS is rapidly developing as a powerful, non-invasive tool for studying the human brain. A pulsed magnetic field creates current flow in the brain and can temporarily excite or inhibit specific areas. TMS of the motor cortex can produce a muscle twitch or block movement; TMS of the occipital cortex can produce visual phosphenes or scotomas. TMS can also alter the functioning of the brain beyond the time of stimulation, offering the potential for therapy and can be used to demonstrate causal brain-behavior relations by either temporarily disrupting information processing in a brain region, generating a short-lived “virtual lesion”, or by entraining resonant stimulation to elicit TMS-induced replay of a stimulus. It's typically a good choice for depression, is used when other depression treatments haven't been effective. 

   tDCS is a popular brain stimulation method that is used to modulate cortical excitability, producing facilitatory or inhibitory effects upon a variety of behaviors, using magnetic field is used to cause an electric current at a specific area of the brain through electromagnetic induction. Two electrodes (positive and negative) are used noninvasively in areas of the brain that will be inhibited or stimulated, respectively. A plastic-enclosed coil of wire is held next to the skull and when activated, produces a magnetic field oriented orthogonal to the plane of the coil. The magnetic field can then be directed to induce an inverted electric current in the brain that activates nearby nerve cells in a manner similar to a current applied superficially at the cortical surface. 

                                    

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Brain StimulationTMS researchElectrodes EPHYSTMS EEGSmall Animal ResearchNeuroscience of ConsciousnessIonic MovementsPriming Effect