Table 1 Comparison of different methods for motor decoding
| Â | Cortical | Peripheral | |||
|---|---|---|---|---|---|
| Â | EEG | ECoG | Intra-cortical | Peripheral nerves | EMG |
Decoding site | Scalp | On the surface of the brain | Penetrated into cortical tissues (e.g. PPC, M1) | Peripheral nerves (e.g. ulna, median, radial nerves) | Muscles |
Types of electrode | Disk electrodes | Flexible electrode array | Utah array | Cuff, intra-neural electrodes | Surface electrodes,needle electrodes |
5-9 cm | <5 mm | 3-5 μm | 0.5-2 mm | >10 mm | |
Frequency spectrum | 0.5-100Hz | 0-500Hz | 100Hz-20kHz | 0.1-10kHz | 0.1Hz-10kHz |
Decodable intention | Movement of different body parts, 2D and 3D direction of movement, different movements of the same limb, individual finger movement | Movement of different body parts, different hand gestures, 2D position and velocity of movement, continous finger position | 2D direction of movement, different hand gestures | Different hand gestures | Different hand gestures, proportional control of grasps |
Signal-to-noise ratio | Low | Medium | High | Low | High |
Signal feature | Bandpower, ERS/ERD | Bandpower, LMP | Spike firing rate, LFP | Action potential firing rate | Various signal features (e.g. RMS, variance, mean absolute value etc.) |
Invasiveness | Low | High | Very high | Medium | Low |
Advantages | Non-invasive, easily deployable | Fine-grained and robust feature, mature surgical procedures as part of epilepsy treatment | Fine-grained and robust feature | Less invasive, potentially contains detailed information about muscle activations | Non-invasive, mature technology, easily deployable |
Disadvantages | Low signal-to-noise ratio, high variability of features between sessions, time-consuming to setup | Invasive, long-term implantation not common | Very invasive, require implantation surgery | Low signal-to-noise ratio | Limited DoF, exessive cross-talk between different channels |