Rat Locomotion Detection Based on Brain Functional Directed Connectivity from Implanted Electroencephalography Signals

Abstract

Previous findings have suggested that the cortex involved in walking control in freely locomotion rats. Moreover, the spectral characteristics of cortical activity showed significant differences in different walking conditions. However, whether brain connectivity presents a significant difference during rats walking under different behavior conditions has yet to be verified. Similarly, whether brain connectivity can be used in locomotion detection remains unknown. To address those concerns, we recorded locomotion and implanted electroencephalography signals in freely moving rats performing two kinds of task conditions (upslope and downslope walking). The Granger causality method was used to determine brain functional directed connectivity in rats during these processes. Machine learning algorithms were then used to categorize the two walking states, based on functional directed connectivity. We found significant differences in brain functional directed connectivity varied between upslope and downslope walking. Moreover, locomotion detection based on brain connectivity achieved the highest accuracy (91.45%), sensitivity (90.93%), specificity (91.3%), and F1-score (91.43%). Specifically, the classification results indicated that connectivity features in the high gamma band contained the most discriminative information with respect to locomotion detection in rats, with the support vector machine classifier exhibiting the most efficient performance. Our study not only suggests that brain functional directed connectivity in rats showed significant differences in various behavioral contexts but also proposed a method for classifying the locomotion states of rat walking, based on brain functional directed connectivity. These findings elucidate the characteristics of neural information interaction between various cortical areas in freely walking rats.

Time-Varying Functional Connectivity of Rat Brain during Bipedal Walking on Unexpected Terrain

“…Some studies have shown that using raw EEG signals or whole-time functional network metrics as features can effectively detect the locomotion state of subjects [ 25 , 58 ]. Our results (Fig.…”

“…Additionally, the size of each electrode point was used to indicate the number of connections the electrode point has. It was worth mentioning that the edge threshold of the network was set to 50% of the strongest connections (i.e., only keep edges that are more than 50% of the strongest connections) [ 25 ]. Finally, the BrainNet Viewer toolbox [ 26 ] was used to visualize the brain functional network.…”

Unexpected Terrain Induced Changes in Cortical Activity in Bipedal-Walking Rats

“…Cats can also actively adjust their limbs to negotiate the obstacles on treadmill, and the motor cortex and posterior parietal cortex play an important role in this process [ 19 , 20 ]. A previous study on rodents has demonstrated that the motor cortex actively participates in the movement control of the hind limbs when rats walk freely on flat ground, a treadmill, or stairs [ 21 ] and the brain connectivity showed different changes when rats walk on slopes with different inclination angles [ 22 ]. In addition, the sensorimotor cortex of rats actively involved in the adjustment of gait during bipedal walking on a treadmill or stairs [ 23 ].…”