Detection of neuronal defensive discharge information transmission and characteristics in periaqueductal gray double-subregions using PtNP/PEDOT:PSS modified microelectrode arrays

Threatened animals respond with appropriate defensive behaviors to survive.It has been accepted that midbrain periaqueductal gray(PAG)plays an essential role in the circuitry system and organizes defensive behavioral responses.However,the role and correlation of different PAG subregions in the expression of different defensive behaviors remain largely unexplored.Here,we designed and manufactured a microelectrode array(MEA)to simultaneously detect the activities of dPAG and vPAG neurons in freely behaving rats.To improve the detection performance of the MEAs,PtNP/PEDOT:PSS nanocomposites were modified onto the MEAs.Subsequently,the predator odor was used to induce the rat’s innate fear,and the changes and information transmission in neuronal activities were detected in the dPAG and vPAG.Our results showed that the dPAG and vPAG participated in innate fear,but the activation degree was distinct in different defense behaviors.During flight,neuronal responses were stronger and earlier in the dPAG than the vPAG,while vPAG neurons responded more strongly during freezing.By applying high-performance MEA,it was revealed that neural information spread from the activated dPAG to the weakly activated vPAG.Our research also revealed that dPAG and vPAG neurons exhibited different defensive discharge characteristics,and dPAG neurons participated in the regulation of defense responses with burst-firing patterns.The slow activation and continuous firing of vPAG neurons cooresponded with the regulation of long-term freezing responses.The results demonstrated the important role of PAG neuronal activities in controlling different aspects of defensive behaviors and provided novel insights for investigating defense from the electrophysiological perspective.

Grid cell remapping under three-dimensional object and social landmarks detected by implantable microelectrode arrays for the medial entorhinal cortex

Grid cells with stable hexagonal firing patterns in the medial entorhinal cortex(MEC)carry the vital function of serving as a metric for the surrounding environment.Whether this mechanism processes only spatial information or involves nonspatial information remains elusive.Here,we fabricated an MEC-shaped microelectrode array(MEA)to detect the variation in neural spikes and local field potentials of the MEC when rats forage in a square enclosure with a planar,three-dimensional object and social landmarks in sequence.The results showed that grid cells exhibited rate remapping under social conditions in which spike firing fields closer to the social landmark had a higher firing rate.Furthermore,global remapping showed that hexagonal firing patterns were rotated and scaled when the planar landmark was replaced with object and social landmarks.In addition,when grid cells were activated,the local field potentials were dominated by the theta band(5–8 Hz),and spike phase locking was observed at troughs of theta oscillations.Our results suggest the pattern separation mechanism of grid cells in which the spatial firing structure and firing rate respond to spatial and social information,respectively,which may provide new insights into how the brain creates a cognitive map.