A system for monitoring includes: multiple EEG sensors spatially positioned on a layer of tissue for capturing EEG signals of a patient； multiple amplifiers coupled with the EEG sensors for amplifying the captured signals； and a low frequency oscillator for generating a synchronizing signal which is distributed to the amplifiers for synchronizing the digitization of the captured signals； wherein each amplifier includes: a voltage controlled oscillator for an adjustable frequency reference； an analog to digital converter for converting the amplified signal to a digital value； and a microcontroller for controlling the frequency of the voltage controlled oscillator and operation of the analog to digital converter by using the synchronizing signal.
