Neuroimaging Techniques

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The functioning of the human mind has been one of the main incentives for philosophers throughout the ages. The need to examine and measure different aspects of the brain anatomy has enhanced the recent developments in neuroimaging techniques. As these techniques have become more affordable and accessible for research, they have allowed an increasingly questioning attitude in making use of neuroimaging methods. Several neuroimaging techniques have provided correlational maps of cognitive processes in the adult human brain at different levels of temporal and spatial detail. Moving beyond a correlational description of the relationship between brain and the behavior was the fresh approach offered by transcranial magnetic stimulation [1], [2], …show more content…

The discharge current flows through the stimulating coil to generate the necessary magnetic pulse. This pulse induces current in electrically conductive regions of the human body. If the induced current is of high amplitude and duration it will stimulate neuromuscular tissue in the same way as with conventional electrical stimulation. The first commercial magnetic stimulators originated from Sheffield in 1985 [16-21]. A typical magnetic stimulator consists of a capacitor charging or discharging alternatively with the appropriate control and safety electronics. Using the charging circuitry the energy storage system (capacitor) is charged to a level which can be up to a maximum of 3000 volts (kV) depending on the device. When the device receives an input signal as a trigger, the energy stored in the capacitor is discharged into the stimulating coil. The stored energy, with the exception of the energy lost in the wiring and capacitor, is transferred to the coil and then returned to the instrument to reduce coil heating. The discharge system consists of a switch and an electronic device, either a power metal oxide semiconductor field effect transistor (MOSFET) or insulated gate bipolar transistor (IGBT) or silicon controlled rectifier (Thyristor), and is capable of switching large currents in a few microseconds. Power MOSFETs, IGBTs and Thyristor conduct current only in one direction. As indicated in Figure 1 there are two types of waveforms: monophasic or biphasic which is commonly found in magnetic stimulation

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