Implantable microsystem for concurrent measurement of brain's action potential and neurotransmitter

Thanks to technological advancements in recent decades, outstanding progress has been made in the field of neuroscience and neural engineering. Although the information processing in the brain is mostly done through neuron's electrical activities, there might be significant information in presynaptic neurochemicals. Recent studies suggest concurrent measurement of interrelated brain's electrical and neurochemical activity may lead to better understanding of brain function in addition to developing optimal neural prosthetics. We present a power efficient implantable CMOS microsystem for simultaneous measurement of Action Potential (AP) and neurotransmitter concentration. It consist of a nano-power neural amplifier for action potential detection and amplification; a nano-power current conveyor potentiostat which senses picoscale to microscale current that corresponds to micromolar neurotransmitter concentration; and a micro-power ΣΔ Analog to Digital Convertor (ADC) to convert the analog signal (AP or neurotransmitter concentration) to digital code. This microsystem is fabricated in CMOS 0.18 μ technology and tested using recorded signals from dorsal premotor cortex (PMd) area of a macaque monkey in our lab.