PMC:2940414 / 17397-19366
Annnotations
{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/2940414","sourcedb":"PMC","sourceid":"2940414","source_url":"https://www.ncbi.nlm.nih.gov/pmc/2940414","text":"Because the NeuroRighter stimulator monitors both the delivered voltage and current, and because it can deliver arbitrary waveforms, including sine waves that sweep across a wide frequency range (temporal resolution of 1 μs), the system can be used to monitor electrode impedance spectra. Impedance (Z, in Ohms) is the opposition to the flow of alternating current at a particular frequency. Measuring microelectrode impedance is important for three reasons – noise, stimulation, and the information that impedance spectroscopy provides about changes in biological tissue. The higher the impedance, the greater is the Johnson–Nyquist noise. Because electrode impedance is largely influenced by electrode surface area, impedance has become associated with tip diameter in neuroscience. It is important to note that impedance is not actually a function of the spatial extent of an electrode, but of its area. That is, it is possible to vary the surface area without varying the diameter, as our group has recently shown (Arcot Desai et al., 2010). Ultimately, the most sensitive, lowest noise microelectrode (for recording single cells) would have the smallest physical extent and an impedance of zero (Ross et al., 2004). Regarding stimulation, with lower electrode impedance, more current can be delivered at lower voltages to evoke a given response (thanks to Ohm's law). This results in smaller stimulation artifacts and potentially less tissue damage, depending on whether such reductions are achieved by increasing capacitance, as in Arcot Desai et al. (2010), or by increasing the current carried via Faradic reactions (Merrill et al., 2005; Cogan, 2008). With electrode impedance spectroscopy (EIS), NeuroRighter can help determine physical and biological reactions to implanted electrodes (Merrill and Tresco, 2005; Lempka et al., 2009). Stimuli can be normalized across an array with electrodes of varying impedance, or as electrode impedance changes over time.","tracks":[{"project":"2_test","denotations":[{"id":"20859448-17271206-38126421","span":{"begin":1214,"end":1218},"obj":"17271206"},{"id":"20859448-15661300-38126422","span":{"begin":1641,"end":1645},"obj":"15661300"},{"id":"20859448-18429704-38126423","span":{"begin":1654,"end":1658},"obj":"18429704"}],"attributes":[{"subj":"20859448-17271206-38126421","pred":"source","obj":"2_test"},{"subj":"20859448-15661300-38126422","pred":"source","obj":"2_test"},{"subj":"20859448-18429704-38126423","pred":"source","obj":"2_test"}]},{"project":"TEST0","denotations":[{"id":"20859448-168-176-173711","span":{"begin":1214,"end":1218},"obj":"[\"17271206\"]"},{"id":"20859448-232-240-173712","span":{"begin":1641,"end":1645},"obj":"[\"15661300\"]"},{"id":"20859448-235-243-173713","span":{"begin":1654,"end":1658},"obj":"[\"18429704\"]"}],"attributes":[{"subj":"20859448-168-176-173711","pred":"source","obj":"TEST0"},{"subj":"20859448-232-240-173712","pred":"source","obj":"TEST0"},{"subj":"20859448-235-243-173713","pred":"source","obj":"TEST0"}]},{"project":"0_colil","denotations":[{"id":"20859448-17271206-173711","span":{"begin":1214,"end":1218},"obj":"17271206"},{"id":"20859448-15661300-173712","span":{"begin":1641,"end":1645},"obj":"15661300"},{"id":"20859448-18429704-173713","span":{"begin":1654,"end":1658},"obj":"18429704"}],"attributes":[{"subj":"20859448-17271206-173711","pred":"source","obj":"0_colil"},{"subj":"20859448-15661300-173712","pred":"source","obj":"0_colil"},{"subj":"20859448-18429704-173713","pred":"source","obj":"0_colil"}]}],"config":{"attribute types":[{"pred":"source","value type":"selection","values":[{"id":"2_test","color":"#94ec93","default":true},{"id":"TEST0","color":"#ec93ae"},{"id":"0_colil","color":"#93c8ec"}]}]}}