Feedback Neuro-Modulation Technology

Neuro Monitoring Technology

A closed-loop smart DBS technology supporting all in one neuromonitoring and neuromodulation could be built around neurophysiological or neurochemical sensing feedback to maintain therapeutic efficacy. Because the brain communicates both electrically and chemically, the most effective treatments for many neurological and psychiatric disorders may involve returning both electrical firing patterns and neurotransmitter release levels back

i. Electrophysiological Monitoring Technique

Early exploration of neural systems focused on understanding how neural systems work at the cellular, tissue, and system levels, and engineering methodologies were developed to detect, process, and model these neural signals. Recently, tremendous progress has been made in the field of neural engineering, not only understanding the mechanism, detection, and processing of the neural signals, but also on restoring the impaired neural systems functions and interfacing the neural systems with artificial devices and machines.

The aim of Neural Engineering team is to develop neurotechnology for restoration & augmentation of human functions via interaction between nervous system and artificial devices.
The Major Two Topics are rewiring the brain and develop next-generation deep brain stimulator.

    Focus in
  • Understanding the coding and processing of information in the brain
  • Quantifying how the coding and processing are altered in the pathological state
  • Developing neuro tech including brain interfaces with artificial devices
    Details of the research
  • Neural Recording and Stimulation in vivo
  • Multichannel Neural Signal Processing and Analysis in vivo
  • Mechanism and Plasticity in vivo
  • Neural Feedback Algorithm and System with DSP chips
ii. Electrochemical Monitoring Technique

The improvement of Deep Brain Stimulation (DBS) has been used for the treatment of the neuro-degenerative disease and neuropsychiatry disease. After DBS surgery, the neurologist occasionally adjusts stimulation parameters to obtain the best therapeutic response in the patient with trial-and-error process.
In order to improve this framework, recently, closed-loop DBS has been suggested with monitoring electrophysiological and neurochemical responses to the stimulation. Our goals in this study are to develop advanced fast-scan cyclic voltammetry (FSCV) measuring neurotransmitters in the brain and to investigate optimized feedback techniques by applying it to animal model of Parkinson's disease.

Fast-scan cyclic voltammetry (FSCV)

Fast-scan cyclic voltammetry (FSCV) is widely used in neuroscience applications. By using simple chemical reaction, oxidation and reduction, it is able to detect certain chemical substances change. As the name implies, the potential is swept from an initial potential to a final potential and then returned to the initial potential, usually at the same sweep rate (Figure 1a, b). The current measured continuously during the sweep is reported against the applied potential (Figure 1c, blue). If a kind of reactive chemical substrate is added in some way, the current is changed at particular voltage point(Figure 1c, red). Hence, the technique provides voltammetric information (current vs. potential) about the substance being detected.

Figure 1 (a) A series of applied waveform through carbon fiber electrode, red bar represents existence of Dopamine (b) Diagram of a potential waveform used in linear sweep (cyclic) voltammetry.
From -0.4V (holding potential) to 1V peak point and back to 0.4V with 400V per second gradient. (c) A cyclic voltammogram before Dopamine releases (blue) and after (red).

This is useful for the purposes of qualitative identification as the voltammograms of a substance is generally unique in its position along the potential axis and its shape. For example, the cyclic voltammogram (CV) of dopamine is easily distinguished from the voltammogram of ascorbate. With a small electrode that rapidly charges to the new applied potential, sweep rates of several hundred volts per second are quite feasible, so the entire CV can be recorded in a matter of milliseconds. This is interesting because the entire CV can be completed in about the same amount of time that it takes to record a single.

Figure 2 Advantages of Fast Scan Cyclic Voltammetry comparing to conventional ways of detecting neurotransmitter in brain.

Interleave FSCV

FSCV technique is powerful measuring method because of its higher time resolution and tinier size of electrode than any other method. Also, it is possible to detect a specific substrate by applying specialized scan-waveform for the substrate. In other words, FSCV have a defect in distinguishing more than 2 substrates at the same time. We propose interleave FSCV that might be a solution of those problems. Conventionally, triangular waveform (-0.4V > 1V > -0.4V, 400V/s) is used to detect dopamine and N-shape waveform (0.2V > 1V > -0.1V > 0.2V) is for serotonin detection. Interleave FSCV is a modified FSCV which is consist of different two scan waveforms. Mixing two other waveforms shows two different voltammograms at one cycle so without changing parameters we can possibly detect different substrate at the same time. It is not only has extended voltammograms, but also shows different characteristic from previously FSCV.

Figure 3. The conventional FSCV waveforms and proposed interleave FSCV waveform. Conventional triangular scan waveform (A) and N-shaped scan waveform for 5-HT (B). Scheme of interleave FSCV scan waveform that we propose (C) and one cycle of its waveform (D).

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