How are memories transferred from short-term to long-term storage? Systems-level memory consolidation is thought to be dependent on the coordinated interplay of cortical slow waves, thalamo-cortical sleep spindles and hippocampal ripple oscillations. However, it is currently unclear how the selective interaction of these cardinal sleep oscillations is organized to support information reactivation and transfer. Here, using human intracranial recordings, we demonstrate that the prefrontal cortex plays a key role in organizing the ripple-mediated information transfer during non-rapid eye movement (NREM) sleep. We reveal a temporally precise form of coupling between prefrontal slow-wave and spindle oscillations, which actively dictates the hippocampal-neocortical dialogue and information transfer. Our results suggest a model of the human sleeping brain in which rapid bidirectional interactions, triggered by the prefrontal cortex, mediate hippocampal activation to optimally time subsequent information transfer to the neocortex during NREM sleep.

Object Many patients undergoing elective thoracic or lumbar fusion procedures are obese, but the contribution of obesity to complications in spine surgery has not been defined. The authors retrospectively assessed the prevalence of obesity in a cohort of patients undergoing thoracic and lumbar fusion and correlate the presence of obesity with the incidence of operative complications. Methods A retrospective review of consecutive patients treated by a single surgeon (J.K.R.) over a 36-month period at either Rush University Medical Center or the Neurological and Orthopedic Institute of Chicago was performed. The authors identified 332 elective thoracic and lumbar spine surgery cases; the cohort was restricted to include only patients with symptomatic degenerative conditions in need of an anterior, posterior, or combined anterior–posterior fusion. Cases of trauma, tumor, and infection and any case in which the procedure was performed for emergency indications were excluded. A total of 97 cases were identified; of these 86 procedures performed in 84 patients had adequate follow-up material for inclusion in the present study. A broad definition of complications was used. Complications were divided into adverse events (minor) and significant complications (major) based on their impact on patient outcome. Stepwise multivariate logistic regression was used to identify which variables had a significant effect on the risk of complications. Variables considered were body mass index (BMI), height, weight, age, sex, presence or absence of diabetes mellitus (DM) and/or hypertension, number of levels fused (single compared with multiple), and type of surgery performed. The mean BMI for the cohort was 28.8 (95% confidence interval 24.4–30.3); 60 patients (71.4%) were considered overweight or obese (BMI ≥ 25). There were 42 complications in 31 patients (36.9%); this included 19 significant complications in 17 patients (20.2%). Logistic regression revealed that the probability of a significant complication was related to BMI (p < 0.04); the chance of a significant complication was 14% with a BMI of 25, 20% with a BMI of 30, and 36% with a BMI of 40. Positioning-related palsies were only found in extremely obese patients (BMI ≥ 40). The probability of minor complication occurrence increased with age (p < 0.02), not BMI. The rate of complications was independent of sex as well as the presence of DM or hypertension. A standard collection of complications occurred, including wound infection (three cases), cerebrospinal fluid leakage (eight cases, one requiring reoperation), deep vein thrombosis (two cases), cardiac events (four cases), symptomatic pseudarthrosis (one case), pneumonia (three cases), prolonged intubation (two cases), urological issues (eight cases), positioning-related palsy (two cases), and neuropathic pain (two cases). Conclusions Obesity is a prevalent condition in patients undergoing elective fusion for degenerative spinal conditions and may increase the prevalence and incidence of perioperative complications. In their analysis, the authors correlated increasing BMI and increased risk of significant postoperative complications. The correlation of obesity and perioperative complications may assist in the preoperative evaluation and selection of patients for surgery.

Background Recently, van Walraven developed a weighted summary score (VW) based on the 30 comorbidities from the Elixhauser comorbidity system. One of the 30 comorbidities, cardiac arrhythmia, is currently excluded as a comorbidity indicator in administrative datasets such as the Nationwide Inpatient Sample (NIS), prompting us to examine the validity of the VW score and its use in the NIS. Methods Using data from the 2009 Maryland State Inpatient Database, we derived weighted summary scores to predict in-hospital mortality based on the full (30) and reduced (29) set of comorbidities and compared model performance of these and other comorbidity summaries in 2009 NIS data. Results Weights of our derived scores were not sensitive to the exclusion of cardiac arrhythmia. When applied to NIS data, models containing derived summary scores performed nearly identically (c statistics for 30 and 29 variable-derived summary scores: 0.804 and 0.802, respectively) to the model using all 29 comorbidity indicators (c = 0.809), and slightly better than the VW score (c = 0.793). Each of these models performed substantially better than those based on a simple count of Elixhauser comorbidities (c = 0.745) or a categorized count (0, 1, 2, or ≥3 comorbidities; c = 0.737). Conclusions The VW score and our derived scores are valid in the NIS and are statistically superior to summaries using simple co-morbidity counts. Researchers wishing to summarize the Elixhauser comorbidities with a single value should use the VW score or those derived in this study.

Object Despite its long-reported successful record, with almost 60 years of clinical use, the technical complexity regarding the placement of stereoelectroencephalography (SEEG) depth electrodes may have contributed to the limited widespread application of the technique in centers outside Europe. The authors report on a simplified and novel SEEG surgical technique in the extraoperative mapping of refractory focal epilepsy. Methods The proposed technique was applied in patients with medically refractory focal epilepsy. Data regarding general demographic information, method of electrode implantation, time of implantation, number of implanted electrodes, seizure outcome after SEEG-guided resections, and complications were prospectively collected. Results From March 2009 to April 2012, 122 patients underwent SEEG depth electrode implantation at the Cleveland Clinic Epilepsy Center in which the authors' technique was used. There were 65 male and 57 female patients whose mean age was 33 years (range 5–68 years). The group included 21 pediatric patients (younger than 18 years). Planning and implantations were performed in a single stage. The time for planning was, on average, 33 minutes (range 20–47 minutes), and the time for implantation was, on average, 107 minutes (range 47–150 minutes). Complications related to the SEEG technique were observed in 3 patients. The calculated risk of complications per electrode was 0.18%. The seizure-free rate after SEEG-guided resections was 62% in a mean follow-up period of 12 months. Conclusions The authors report on a safe, simplified, and less time-consuming method of SEEG depth electrode implantation, using standard and widely available surgical tools, making the technique a reasonable option for extraoperative monitoring of patients with medically intractable epilepsy in centers lacking the Talairach stereotactic armamentarium.

Recognizing motivationally salient information is critical to guiding behaviour. The amygdala and hippocampus are thought to support this operation, but the circuit-level mechanism of this interaction is unclear. We used direct recordings in the amygdala and hippocampus from human epilepsy patients to examine oscillatory activity during processing of fearful faces compared with neutral landscapes. We report high gamma (70–180 Hz) activation for fearful faces with earlier stimulus evoked onset in the amygdala compared with the hippocampus. Attending to fearful faces compared with neutral landscape stimuli enhances low-frequency coupling between the amygdala and the hippocampus. The interaction between the amygdala and hippocampus is largely unidirectional, with theta/alpha oscillations in the amygdala modulating hippocampal gamma activity. Granger prediction, phase slope index and phase lag analysis corroborate this directional coupling. These results demonstrate that processing emotionally salient events in humans engages an amygdala-hippocampal network, with the amygdala influencing hippocampal dynamics during fear processing.

Early resection may improve seizure outcomes of FLE surgery, particularly in children.

Obesity is a prevalent condition in patients undergoing elective fusion for degenerative spinal conditions and may increase the prevalence and incidence of perioperative complications. In their analysis, the authors correlated increasing BMI and increased risk of significant postoperative complications. The correlation of obesity and perioperative complications may assist in the preoperative evaluation and selection of patients for surgery.

SUMMARY How do we remember emotional events? While emotion often leads to vivid recollection, the precision of emotional memories can be degraded, especially when discriminating among overlapping experiences in memory (i.e., pattern separation). Communication between the amygdala and the hippocampus has been proposed to support emotional memory, but the exact neural mechanisms remain unclear. Here, we used intracranial recordings in pre-surgical epilepsy patients to show that successful pattern separation of emotional stimuli is associated with theta band (3–7 Hz)-coordinated bidirectional interactions between the amygdala and the hippocampus. In contrast, discrimination errors (i.e., failure to discriminate similar stimuli) were associated with alpha band (7–13 Hz)-coordinated unidirectional influence from the amygdala to the hippocampus. These findings imply that alpha band synchrony may impair discrimination of similar emotional events via the amygdala-hippocampal directional coupling, which suggests a target for treatments of psychiatric conditions such as posttraumatic stress disorder, in which aversive experiences are often overgeneralized.