# Physiological properties of brain-machine interface input signals

###### tags: `論文摘要` `穩定性` `訊號介紹`

- Link: [https://doi.org/10.1152/jn.00070.2017](https://doi.org/10.1152/jn.00070.2017)
- MLA: Slutzky, Marc W., and Robert D. Flint. "Physiological properties of brain-machine interface input signals." Journal of neurophysiology 118.2 (2017): 1329-1343.
- 年分: 2017
- 期刊: Journal of neurophysiology

## 主旨

全面介紹各類型BCI

## BCI分類

- Motor BMIs
- Rreactive BMIs
using evoked potentials
- Passive BMIs
do not attempt direct control
- sensory/afferent BMIs

## BCI領域問題 - 訊號

1. 維持時間
2. 穩定性
3. 訊號中帶有的資訊量

## 訊號類別

1. action potentials (spikes)
2. intracortical local field potentials (LFPs)
3. subdural signals (electrocorticography, or ECoG)
4. epidural field potentials (EFPs)
5. EEG
6. blood flow near-infrared spectroscopy (NIRS)
7. functional magnetic resonance imaging (fMRI)
8. calcium imaging
9. magnetoencephalography (MEG)

## 侵入式電極訊號介紹

These recordings can be bandpass filtered at around 0.5–300 Hz, to extract local field potentials (LFPs), or filtered in a higher band (300 Hz−12 kHz) to extract action potentials, or spikes.

Spikes can be sorted into single units or simply thresholded, also called multiunit spikes (MSPs).

## 侵入式電極訊號相關性 Movement-Related Information

During reaching and grasping, SUA from motor cortex provides a great deal of information about both the intended movement direction, arm and hand kinematics, joint torques, and arm muscle activity.

Multiunit spikes have been shown to provide essentially equivalent decoding performance to single units, with one study showing a small improvement from sorting.

Recent studies have shown that LFPs are very informative, with nearly as much information as spikes about kinematics and muscle activity during reaching and grasping.The largest amount of this information is contained within the power of the high-gamma band (~70–300 Hz) of the LFP.

## 侵入式電極長期使用問題

大多數問題是在電極設計上面

- 剛性電極(microwire, silicon)會導致腦組織發炎，進而造成阻抗增加
- 阻抗增加可能不是由於膠質瘢痕所造成，而是由於黏著在電極上的其他蛋白引起
- 電極本身會導致慢性出血，最終導致細胞死亡
- 材料老化導致損壞
- 電極斷裂導致損壞

LFP因為是來自於多個神經細胞的群體反映，因此一般認為穩定性會比SUA好

## 侵入式電極穩定性問題

電極的穩定性能夠使得使用者能夠**熟悉控制**，也能**減少重新校準**的需要

- 定義方式
1. waveform characteristics of the spikes themselves

> Dickey, Adam S., et al. "Single-unit stability using chronically implanted multielectrode arrays." Journal of neurophysiology 102.2 (2009): 1331-1339.

2. the stability of a signal’s movement-related information over time

> Chestek, Cynthia A., et al. "Long-term stability of neural prosthetic control signals from silicon cortical arrays in rhesus macaque motor cortex." Journal of neural engineering 8.4 (2011): 045005.

- (Fig A) correlations between decoded and actual velocity remained stable for 1–2 days
- (Fig B) unit對方向的偏好持續時間