Methods and apparatuses for amplitude-modulated ensemble waveforms for neurostimulation

A method of modulating a user's cognitive state by transdermal electrical stimulation, the method comprising:

• delivering an ensemble current waveform for application between two or more electrodes, wherein the ensemble current waveform comprises a series of component waveforms that are sequentially delivered, wherein the component waveforms comprise biphasic pulses and wherein each component waveform in the series is different from a component waveform immediately before it and/or immediately after it in the series by one or more of:
• a duration, a current amplitude, a frequency, a percent charge imbalance, and a percent duty cycle;
• wherein, prior to delivery, one or more of the component waveforms of the ensemble current waveform is modulated by setting the current amplitude to zero at a modulation frequency for a modulation duration that does not result in truncated pulses in the delivered waveform;
• wherein the modulation duration is the inverse of the modulation frequency, and comprises a bursting duty cycle divided by the modulation frequency, further wherein the modulation duration is adjusted to prevent truncation of pulses in the delivered waveform.