Optogenetic Brain-Computer Interfaces

Abstract

The brain-computer interface (BCI) is one of the most powerful tools in neuroscience and generally includes a recording system, a processor system, and a stimulation system. Optogenetics has the advantages of bidirectional regulation, high spatiotemporal resolution, and cell-specific regulation, which expands the application scenarios of BCIs. In recent years, optogenetic BCIs have become widely used in the lab with the development of materials and software. The systems were designed to be more integrated, lightweight, biocompatible, and power efficient, as were the wireless transmission and chip-level embedded BCIs. The software is also constantly improving, with better real-time performance and accuracy and lower power consumption. On the other hand, as a cutting-edge technology spanning multidisciplinary fields including molecular biology, neuroscience, material engineering, and information processing, optogenetic BCIs have great application potential in neural decoding, enhancing brain function, and treating neural diseases. Here, we review the development and application of optogenetic BCIs. In the future, combined with other functional imaging techniques such as near-infrared spectroscopy (fNIRS) and functional magnetic resonance imaging (fMRI), optogenetic BCIs can modulate the function of specific circuits, facilitate neurological rehabilitation, assist perception, establish a brain-to-brain interface, and be applied in wider application scenarios.

Keywords: brain–computer interface; electrode; multimodal; optogenetic.

Figure 2

Examples of optogenetic BCI applications. In an example of enhancing cognitive function, optogenetic stimulation of firing inhibition on the troughs of endogenous theta rhythms in the mouse hippocampus increased the probability of correct selection when the mice were in the retrieval arm [90]. In an example of neurotherapy, detecting the onset of epilepsy and providing optogenetic stimulation can be effective in alleviating it [8]. In an assisted perception example, the primary somatosensory cortex (vS1) was given light stimulus feedback along with a water reward, while the mouse controlled the primary motor cortex (vM1) firing rate within a certain range, that is, mouse-specific whisker movement [101]. After training, the mouse’s licking behavior relied on the feedback of artificial light stimulation provided in vS1, which proved that the light stimulation made the mice feel that they were in contact with the virtual stick that provided water. In a brain–computer–brain interface example, calcium imaging signals related to locomotion velocity in the brainstem nuclei (NI) of autonomously moving mice were used to encode optogenetic stimuli in controlled mice, modulating their locomotor patterns so that they closely mimicked the movements of the active locomotor mice [102]. Blue arrows indicate brain-machine information flow and pink arrows indicate machine-brain information flow.

Figure 1

(a) Upper half: mechanism of ChR2. When irradiated with blue light, ion channels open, leading to sodium inward flow, causing depolarization. Lower half: NpHR mechanism. When irradiated with yellow light, the ion channel opens, leading to chloride ion inward flow, resulting in hyperpolarization. (b) Upper half: open-loop system. The output is generated directly through the processing and stimulation systems with no feedback control. Lower half: closed-loop system. Outputs are generated through the processing system, the stimulation system, and the recording system, using the recording system as a feedback control to modulate the outputs. (c) Frame diagram of the EEG-based optogenetic BCI. The recording system reads signals from the animal’s brain through electrodes, performs a series of pre-processing, and then transfers the data to the processing system. The processing system analyzes and decodes the signal read by the recording system and encodes the signal according to the analysis results. After the encoding is completed, the stimulus system is controlled to output the signal. The stimulus system gives corresponding optogenetic stimulation to the animal according to the encoding of the processing system.

Figure 3

(a) Future development trends. (b) Spatial and temporal resolutions of different neural interface technologies.