Due to the sparse encoding character of the human visual cortex and the scarcity of paired training samples for {images, fMRIs}, voxel selection is an effective means of reconstructing perceived images from fMRI. However, the existing data-driven voxel selection methods have not achieved satisfactory results.
Here, a novel deep reinforcement learning-guided sparse voxel (DRL-SV) decoding model is proposed to reconstruct perceived images from fMRI. We innovatively describe voxel selection as a Markov decision process (MDP), training agents to select voxels that are highly involved in specific visual encoding.
Experimental results on two public datasets verify the effectiveness of the proposed DRL-SV, which can accurately select voxels highly involved in neural encoding, thereby improving the quality of visual image reconstruction.
We qualitatively and quantitatively compared our results with the state-of-the-art (SOTA) methods, getting better reconstruction results. We compared the proposed DRL-SV with traditional data-driven baseline methods, obtaining sparser voxel selection results, but better reconstruction performance.
DRL-SV can accurately select voxels involved in visual encoding on few-shot, compared to data-driven voxel selection methods. The proposed decoding model provides a new avenue to improving the image reconstruction quality of the primary visual cortex.
With the arrival of the new generation of artificial intelligence wave, new human-robot interaction technologies continue to emerge. Brain–computer interface (BCI) offers a pathway for state monitoring and interaction control between human and robot. However, the unstable mental state reduce the accuracy of human brain intent decoding, and consequently affects the precision of BCI control.
This paper proposes a hybrid BCI-based shared control (HB-SC) method for brain-controlled robot navigation. Hybrid BCI fuses electroencephalogram (EEG) and electromyography (EMG) for mental state monitoring and interactive control to output human perception and decision. The shared control based on multi-sensory fusion integrates the special obstacle information perceived by humans with the regular environmental information perceived by the robot. In this process, valid BCI commands are screened by mental state assessment and output to a layered costmap for fusion.
Eight subjects participated in the navigation experiment with dynamically changing mental state levels to validate the effects of a hybrid brain-computer interface through two shared control modes. The results show that the proposed HB-SC reduces collisions by 37.50 %, improves the success rate of traversing obstacles by 25.00 %, and the navigation trajectory is more consistent with expectations.
The HB-SC method can dynamically and intelligently adjust command output according to different brain states, helping to reduce errors made by subjects in a unstable mental state, thereby greatly enhancing the system's safety.
In vitro models tailored for spinal cord ischemia-reperfusion injury are pivotal for investigation of the mechanisms underlying spinal cord injuries. We conducted a two-phased study to identify the optimal conditions for establishing an in vitro model of spinal cord ischemia–reperfusion injury using primary rat spinal motor neurons.
In the first phase, cell cultures were subjected to oxygen deprivation (OD) only, glucose deprivation (GD) only, or simultaneous deprivation of oxygen and glucose [oxygen-glucose deprivation (OGD)] for different durations (1, 2, and 6 h). In the second phase, different durations of re-oxygenation (1, 12, and 24 h) were applied after 1 h of OGD to determine the optimal duration simulating reperfusion injury.
GD for 6 h significantly reduced cell viability (91 % of control, P<0.001) and increase cytotoxicity (111 % of control, P<0.001). OGD for 1 h and 2 h, resulted in a significant decrease in cell viability (80 % of control P<0.001, respectively), and increase in cytotoxicity (130 % of control, P<0.001, respectively). Re-oxygenation for 1, 12, and 24 h worsened ischemic injury following 1 h of OGD (all P<0.05).
Our results may provide a valuable guide to devise in vitro models of spinal cord ischemia–reperfusion injury using primary spinal motor neurons.