Objective: neurocognitive effects of extremely low frequencies electromagnetic fields (ELF-EMF) are not known. Therefore, we evaluated the effects of ELF-EMF on cognitive functions specially working memory, serum levels of stress hormones, glucocorticoid receptor gene expression, and anatomical dimensions of the brain in nonhuman primates.

Materials and Methods: To this end, four rhesus monkeys were irradiated by 0.7 microtesla ELF-EMF either at 5 or 30 Hz (two animals per exposure condition), 4 h a day, for 30 days. Working memory was assessed by delayed response task, before and after the irradiation phase. Serum stress hormones were measured by enzyme-linked immunosorbent assay. Lymphocyte GR mRNA was measured using semi-quantitative reverse transcriptase polymerase chain reaction. The monkeys’ brains were scanned using magnetic resonance imaging before and after irradiation.

Results: Results showed that irradiation at 30 Hz disrupted working memory. This was associated with increases in serum cortisol and ACTH. Serum epinephrine and lymphocyte GR mRNA were not significantly influenced by 30 Hz irradiation. Irradiation at 5 Hz did not affect working memory, stress hormones, and GR gene expression. No anatomical changes were found in the PFA, hippocampus, and amygdala at either frequency.

Conclusion: Compared with the 5-Hz exposure condition, 30-Hz ELF-EMF exposure was associated with impaired working memory and increased serum cortisol and ACTH levels. These findings provide preliminary evidence of a frequency-dependent association between ELF-EMF exposure, stress-related hormonal responses, and working-memory performance.