To investigate the real-time biological effects of 2650 MHz radiofrequency radiation (RFR) on learning and memory as well as calcium activity patterns of hippocampal CA1 pyramidal neurons of mice.

Adult male C57BL/6N mice were randomly assigned to control (CON) and RFR groups before being exposed to 2650 MHz RFR for 3 hours in an electromagnetic reverberation chamber. Within 1 hour after exposure, changes in learning and memory were assessed using novel object recognition (NOR), object location recognition (OLR), and temporal order recognition (TOR) tests. Calcium activity of CA1 pyramidal neurons was monitored before, during, and after exposure using genetically encoded calcium imaging combined with fiber photometry. Neuronal activation was evaluated by c-Fos immunofluorescence staining.

Compared with the CON group, RFR-exposed mice showed significantly reduced preference indices for target objects in the NOR (P < 0.001), OLR (P < 0.01), and TOR (P < 0.01) tests within 1 hour post-exposure. During RFR exposure, neuronal calcium signals exhibited an abnormal high-frequency but low-amplitude pattern, characterized by increased event frequency (P < 0.05) and decreased single-event amplitude (P < 0.05). Furthermore, the immunofluorescence intensity of c-Fos in the hippocampal CA1 region was significantly reduced (P < 0.05).

2650 MHz radiofrequency radiation exposure can induce immediate effects, such as abnormalities in calcium signaling patterns and suppressed excitability of pyramidal neurons in the hippocampal CA1 region, ultimately leading to impaired learning and memory functions.