Fig. 2.

Example of wave forms and parametric manipulations used for brain stimulation in ICSS. (A) Alternating sine-wave current was often used in early ICSS studies, and monophasic square-wave current is typical of more recent ICSS studies. Square-wave current permits greater control over stimulus onset and offset, and monophasic square waves are typically used when only the cathode is implanted in brain. Biphasic square-wave current is also commonly used with twisted electrodes, in which both the cathode and anode are implanted in brain. (B) Changes in pulse amplitude produce changes in the identity of the activated neurons, such that increased amplitude activates neurons of progressively smaller diameter located progressively farther from the electrode tip. Changes in pulse frequency alter the firing rate of activated neurons.