CREB1 and insomnia measurement: In the suprachiasmatic nucleus (SCN), EGFR shows pronounced circadian transcriptional responses and regulates rhythm-related pathways through transcription factors such as CREB, AP1, and Rorα, providing a molecular basis for the SCN to integrate environmental signals with the intrinsic biological clock.[56] Dysregulation of this mechanism may lead to circadian rhythm disturbances and insomnia.