The association between working memory precision and the nonlinear dynamics of frontal and parieto-occipital EEG activity.

Electrophysiological working memory (WM) research shows brain areas communicate via macroscopic oscillations across frequency bands, generating nonlinear amplitude modulation (AM) in the signal. Traditionally, AM is expressed as the coupling strength between the signal and a prespecified modulator at a lower frequency. Therefore, the idea of AM and coupling cannot be studied separately. In this study, 33 participants completed a color recall task while their brain activity was recorded through EEG. The AM of the EEG data was extracted using the Holo-Hilbert spectral analysis (HHSA), an adaptive method based on the Hilbert-Huang transforms. The results showed that WM load modulated parieto-occipital alpha/beta power suppression. Furthermore, individuals with higher frontal theta power and lower parieto-occipital alpha/beta power exhibited superior WM precision. In addition, the AM of parieto-occipital alpha/beta power predicted WM precision after presenting a target-defining probe array. The phase-amplitude coupling (PAC) between the frontal theta phase and parieto-occipital alpha/beta AM increased with WM load while processing incoming stimuli, but the PAC itself did not predict the subsequent recall performance. These results suggest frontal and parieto-occipital regions communicate through theta-alpha/beta PAC. However, the overall recall precision depends on the alpha/beta AM following the onset of the retro cue.

Cumulative live birth and surplus embryo incidence after frozen-thaw cycles in PCOS: how many oocytes do we need?

PURPOSE: This study aimed to evaluate the cumulative live birth rate (CLBR) and surplus embryo rate of polycystic ovarian syndrome (PCOS) patients during in vitro fertilization and embryo transfer (IVF-ET) treatment. METHODS: In this retrospective cohort study, we analyzed 1142 PCOS patients who underwent first IVF in our institution between January 2011 and December 2014. All patients were categorized into five groups according to the number of oocytes retrieved. Main outcomes include CLBR and surplus embryo rate. RESULTS: A strong correlation was observed between number of oocytes retrieved and CLBR as well as surplus embryo rate in PCOS patients. CLBR was elevated with the increasing number of oocytes and plateaued when oocyte number was up to ten, whereas the surplus embryo rate steadily increased in line with the increase of oocyte number. Patients transferred with frozen embryos showed higher CLBR and LBR during first ET than patients transferred with fresh embryos. CONCLUSIONS: For PCOS patients, retrieving more than ten oocytes leads to no significant benefit to CLBR but generates surplus embryos. Thus, moderate ovarian stimulation should be reconsidered during IVF treatment.