Impact of Sleep Apnea on Nocturnal Parasympathetic Activity in Atrial Fibrillation Patients After Catheter Ablation　- Implications for Heart Rate Variability Analysis.

BACKGROUND: The impact of sleep apnea (SA) on heart rate variability (HRV) in atrial fibrillation (AF) patients has not been investigated. METHODS AND RESULTS: Of 94 patients who underwent AF ablation between January 2021 and September 2022, 76 patients who had a nocturnal Holter electrocardiography and polysomnography conducted simultaneously were included in the analysis. A 15-min duration of HRV, as determined by an electrocardiogram during apnea and non-apnea time, were compared between patients with and without AF recurrence at 12 months' postoperatively. Patients had a mean age of 63.4±11.6 years, 14 were female, and 20 had AF recurrence at 12 months' follow-up. The root mean square of the difference between consecutive normal-to-normal intervals (RMSSD, ms) an indicator of a parasympathetic nervous system, was more highly increased in patients with AF recurrence than those without, during both apnea and non-apnea time (apnea time: 16.7±4.5 vs. 13.5±3.3, P=0.03; non-apnea time: 20.9±9.5 vs. 15.5±5.9, P<0.01). However, RMSSD during an apneic state was decreased more than that in a non-apneic state in both groups of patients with and without AF recurrence (AF recurrence group: 16.7±4.5 vs. 20.9±9.5, P<0.01; non-AF recurrence group; 13.5±3.3 vs. 15.5±5.9, P=0.03). Consequently, the effect of AF recurrence on parasympathetic activity was offset by SA. Similar trends were observed for other parasympathetic activity indices; high frequency (HF), logarithm of HF (lnHF) and the percentage of normal-to-normal intervals >50 ms (pNN50). CONCLUSIONS: Without considering the influence of SA, the results of nocturnal HRV analysis might be misinterpreted. Caution should be taken when using nocturnal HRV as a predictor of AF recurrence.

Supranormal orientation selectivity of visual neurons in orientation-restricted animals.

Altered sensory experience in early life often leads to remarkable adaptations so that humans and animals can make the best use of the available information in a particular environment. By restricting visual input to a limited range of orientations in young animals, this investigation shows that stimulus selectivity, e.g., the sharpness of tuning of single neurons in the primary visual cortex, is modified to match a particular environment. Specifically, neurons tuned to an experienced orientation in orientation-restricted animals show sharper orientation tuning than neurons in normal animals, whereas the opposite was true for neurons tuned to non-experienced orientations. This sharpened tuning appears to be due to elongated receptive fields. Our results demonstrate that restricted sensory experiences can sculpt the supranormal functions of single neurons tailored for a particular environment. The above findings, in addition to the minimal population response to orientations close to the experienced one, agree with the predictions of a sparse coding hypothesis in which information is represented efficiently by a small number of activated neurons. This suggests that early brain areas adopt an efficient strategy for coding information even when animals are raised in a severely limited visual environment where sensory inputs have an unnatural statistical structure.