Journal of Bionic Engineering (2024) 21:866–876 https://doi.org/10.1007/s42235-023-00464-5 

Movement Trend Alterations in the Periaqueductal Gray (PAG)?Employed Ratbot Navigation Are Correlated with Stimulation Parameters 

Sina Khajei1  · Abed Khorasani1,2 · Mohammad Reza Afarinesh1,2  · Vahid Sheibani1,2 

1 Faculty of Robot Science and Engineering, Northeastern University, Shenyang 110819, China 2 School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, China

AbstractIn previous studies, Periaqueductal Gray (PAG) stimulation was used to stop ratbots from moving. Due to the homology between the PAG and the intercollicular nucleus, which has been used for forward movement in birds, we investigated the possibility of PAG application to induce forward locomotion for the frst time. Using a corridor maze, the traveled distances via PAG electrical stimulation were examined in nine Wistar male rats during three sessions. A custom-designed stimulator was developed to apply the stimulation. The results showed reductions in responses to stimulation over time. Accordingly, the traveled distances had negative slopes during the consecutive trials (in 8 out of the 9 rats), and the slope mean was signifcantly diferent from zero. There was a strong correlation between the stimulation parameters (electric Charge per Phase (CPP) and the Number of Pulses (NP)) and the observed slopes. The negative Movement Slopes (MS) were highly correlated with the CPP and the NP, as the Pearson's linear correlation coefcients were ? 0.87 and ? 0.79, respectively. The MS-CPP coefcients of determination (R-squared) were also between 0.76 and 0.95. In addition, the MS-NP coefcients of determination were between 0.63 and 0.87. Thus, it is concluded that the electrical stimulation parameters infuence the behavioral outcomes directly. Furthermore, the PAG area may be considered a suitable candidate for forward locomotion control in the future if the area is harnessed efectively to prevent undesirable chaotic behaviors. 

Keywords Periaqueductal Gray (PAG) · Navigation · Ratbot · Animal-robot · Forward locomotion · Movement slope