4、Stimulation microelectrode technologies[edit]

  Fig 7 Utah microelectrode array   Microelectrodes are one of the key components of the  neurostimulation, which deliver

the current to neurons。 Typical microelectrodes have  three main  components:  a  substrate (the carrier), a conductive metal layer, and an insulation material。 In cochlear implants, microelectrodes are formed from platinum-iridium alloy。 State-of-the-art electrodes include deeper insertion to better match the tonotopic place of stimulation to the frequency band assigned to each electrode channel, improving efficiency of stimulation, and reducing insertion related trauma。 These cochlear implant electrodes are either straight or spiral such as Med El Combi 40+ and Advanced Bionics Helix microelectrodes respectively。 In visual implants, there are two types of electrode arrays called planar type or three  dimensional needle or pillar type, where needle type array such as Utah array is mostly used for cortical

and optic nerve stimulations and rarely used in retinal implants due to the possible damage of retina。 However, a pillar-shaped gold electrode array on thin-film polyimide has been used in an extraocular implant。 On the other hand, planar electrode arrays are formed from flexible polymers, such as silicone, polyimide, andparylene as candidates for retinal implants。 Regarding to DBS microelectrodes an array, which can be controlled independently, distributed throughout the target nucleus would permit precise control of the spatial distribution of the stimulation, and thus, allow better personalized DBS。 There are several requirements for DBS microelectrodes that include long lifetime without injury to the tissue or    degradation    of    the    electrodes,    customized    for    different     brain  sites, long-term biocompatibility of the material, mechanically durable in order to reach the target without being damaged during handling by the implant surgeon, and finally uniformity of performance across the microelectrodes in a particular array。 Tungsten microwire, iridium microwires, and platinum–iridium microelectrodes are the examples of microelectrode used inDBS。[6]  Silicon   Carbide is   a   potential   interesting   material   for   realizing biocompatible

semiconductor devices。[26]文献综述

三、Migraine therapy[edit]

In March 2014, the FDA approved Cefaly, a device  that  stimulates  the  trigeminal nerve with an externally applied electrode。 While it does not relieve migraines when they are in progress, users who wear the device for 20 minutes a day suffer fewer migraines a month, according to clinical trials。[27]

四、Non-clinical(laboratory) stimulation applications[edit]

In addition to the enormous usage of neurostimulation for clinical applications, it is also used widely in laboratories started dates back to 1920s by people link Delgado who used stimulation as an experimental manipulation to study basics of how the brain works。 The primary works were on the reward center of the brain in which stimulation of those structures led to pleasure that requested more stimulation。 Another most recent example is the electrical stimulation of the MT area of primary visual cortex to bias perception。 In particular, the directionality of motion is represented in a regular way in the MT area。 They presented monkeys with moving images on screen and monkey throughput was to determine what the direction  is。  They  found  that  by  systematically  introducing  some  errors  to  the monkey's

responses, by stimulating the MT area which is responsible for perceiving the motion in another direction, the monkey responded to somewhere in between the actual motion and the stimulated one。 This was an elegant use of stimulation to show that MT area is essential in the actual perception of motion。 Within the memory field, stimulation is used very frequently to test the strength of the connection between one bundle of cells to another by applying a small current in one cell which  results  in  the  release  of  neurotransmitters  and  measuring the postsynaptic potential。Generally, a short but high-frequency current in the range of 100 Hz helps  strengthening the  connection  known as long-term potentiation。  However, longer    but