System on Chip for Closed Loop Neuromodulation Based on Dual Mode Biosignals

Abstract

Closed loop neuromodulation, where the stimulation is controlled autonomously based on physiological events, has been more effective than open loop techniques. In the few existing closed loop implementations which have a feedback, indirect non-neurophysiological biomarkers have been typically used (e.g. heart rate, stomach distension). Although these biomarkers enable automatic initiation of neural stimulation, they do not enable intelligent control of stimulation dosage. In this paper, we present a novel closed loop neuromodulation System-on-Chip (SoC) based on a dual signal mode that is detecting both electrical and chemical signatures of neural activity. We use vagus nerve stimulation (VNS) as a design case here. Vagal chemical (pH) signal is detected and used for initiating VNS and vagal compound action potential (CAP) signals are used to determine the stimulation dosage and pattern. Although we used the paradigm of appetite control and neurometabolic therapies for developing the algorithms for neurostimulation control, the SoC described here can be utilised for other types of closed loop neuromodulation implants.

Closed-Loop Implantable Therapeutic Neuromodulation Systems Based on Neurochemical Monitoring

“…Recently, an electrode was developed by Vajari et al (2018), which incorporates the ability to record both neurochemical, neuro-electrical recording and electrical stimulation. This is a desirable addition for CNS based therapy, but is necessary for complete closed-loop in a PNS based closed-loop neuromodulation system (Mirza et al, 2017, 2019).…”

“…Both decision making and stimulation dose selection algorithms have to undergo a training phase to enable autonomous operation. The training phase can be conducted on in vivo data (Behrend et al, 2009; Trevathan et al, 2015; Bozorgzadeh et al, 2016; Mirza et al, 2019), by recording the neurochemical response to different stimulation parameters. This is followed by cross validation to judge the precision of decision making and stimulation model control algorithms.…”

Iridium Oxide-Based Potassium Sensitive Microprobe With Anti-Fouling Properties

“…Such sensory capability can be combined with a signal processing and decision algorithm, and stimulation module. These technologies together with the attractive possibility to form a novel closed-loop stimulation system will allow the opportunity to answer two main questions for closed-loop stimulation, that is, when to stimulate as well as the type of stimulation dosage invoked [16,17,18]. The sensor can be readily extended into sensor arrays [19,20].…”

A Convolutional Neural Network for Classification of Nerve Activity Based on Action Potential Induced Neurochemical Signatures

“…It has also been shown to offer better therapeutic outcome [1], [2]. However, a significant step towards achieving an effective closed-loop system is selection of an appropriate symptomatic biomarker [3].…”

“…The latter is generally observed in CNS, more specifically in the presence of cell bodies where inter-neuron response transmission occurs. More research has been performed in observing neurotransmitters compared to ionic responses with the primary reason being difficulty in fabricating implantable, penetrating, ion-selective microelectrodes until recently [3]. Fig.…”