BACKGROUND: Aneurysmal subarachnoid hemorrhage (aSAH) can lead to cognitive impairment (CI), but underlying neural mechanisms remain to be elucidated. MATERIALS AND METHODS: To predict long-term CI after aSAH, resting electroencephalography (EEG) was measured in 112 patients hospitalized with a diagnosis of aSAH ( n = 66) or unruptured intracranial aneurysms (controls) ( n = 46). A neuropsychological battery was administered 8-24 months after discharge. RESULTS: Power spectrum analysis in the parietal-occipital lobe showed significantly higher power theta vs. alpha oscillations in patients with CI after aSAH. The power of theta and alpha oscillations were significantly correlated with multiple cognitive scale scores on the neuropsychological battery. A neural model was established, which showed that connectivity between inhibitory and excitatory neurons in neural circuits contributed to changes in theta and alpha oscillations and CI in aSAH. CONCLUSION: The data collection, analysis, and computational model established in this study can serve as a new paradigm for other clinical studies investigating CI.