Cross-regional phase amplitude coupling supports the encoding of episodic memories.

Phase amplitude coupling (PAC) between theta and gamma oscillations represents a key neurophysiological mechanism that promotes the temporal organization of oscillatory activity. For this reason, PAC has been implicated in item/context integration for episodic processes, including coordinating activity across multiple cortical regions. While data in humans has focused principally on PAC within a single brain region, data in rodents has revealed evidence that the phase of the hippocampal theta oscillation modulates gamma oscillations in the cortex (and vice versa). This pattern, termed cross-regional PAC (xPAC), has not previously been observed in human subjects engaged in mnemonic processing. We use a unique dataset with intracranial electrodes inserted simultaneously into the hippocampus and seven cortical regions across 40 human subjects to (1) test for the presence of significant cross-regional PAC (xPAC), (2) to establish that the magnitude of xPAC predicts memory encoding success, (3) to describe specific frequencies within the broad 2-9 Hz theta range that govern hippocampal-cortical interactions in xPAC, and (4) compare anterior versus posterior hippocampal xPAC patterns. We find that strong functional xPAC occurs principally between the hippocampus and other mesial temporal structures, namely entorhinal and parahippocampal cortices, and that xPAC is overall stronger for posterior hippocampal connections. We also show that our results are not confounded by alternative factors such as inter-regional phase synchrony, local PAC occurring within cortical regions, or artifactual theta oscillatory waveforms.

Sex Differences in Postoperative Complications and Functional Status After Deformity Correction Surgery: Do Men Fare Better Than Women?

OBJECTIVE: We investigated whether a sex-related difference exists in the postoperative complication risk and health-related quality of life measures after surgery for adult spinal deformity. METHODS: We performed a retrospective study of 156 adult patients with a diagnosis of adult spinal deformity who had undergone spinal surgery. The primary outcome variables included the postoperative complication rates and changes in the health-related quality of life measures. Adjusted odds ratios were estimated by multivariate logistic regression with the inclusion of covariate terms for sex, smoking, preoperative optimization, American Society of Anesthesiologists grade, depression, osteoporosis, invasiveness of surgery (number of vertebral levels fused), and baseline functional disability. RESULTS: At presentation, the women were more likely to be smokers (74 women [71.15%]; 23 men [42.31%]; P = 0.01) and to have a greater prevalence of depression (36 women [34.62%]; 10 men [19.23%]; P = 0.06). The women had also presented with more severe baseline pain (visual analog scale for back pain score, 7.24 vs. 6.00 [P = 0.02]; visual analog scale for leg pain score, 5.87 vs. 5.59 [P = 0.07]) and worse functional disability (patient-reported outcomes measurement information system score, 6.82 vs. 5.65 [P = 0.01]; Oswestry disability index, 45.42 vs. 37.07 [P = 0.01]). However, postoperatively, the women experienced greater improvement in pain and disability compared with the men. The unadjusted odds of a postoperative complication was greater for the women (odds ratio, 1.14; 95% confidence interval, 0.55-2.33). On multivariate logistic regression analysis, the association between sex and postoperative complications was attenuated after controlling for other baseline variables. CONCLUSIONS: In the present study, after adjustment for important baseline prognostic factors, no differences were found in the postoperative complication rates or extent of functional improvement when stratified by sex. Both sexes responded equally well to corrective surgery for symptomatic adult spinal deformity.