Single versus double retrograde intramedullary nail technique for treatment of displaced proximal humeral fractures in children: A retrospective cohort study.

Background: Highly displaced proximal humeral fractures in children with low remodeling potential need to be reduced and fixed. The use of two flexible retrograde nails became the most popular fixation technique due to the excellent functional outcome, the low complication rates, and the possibility of early mobilization. A modified single retrograde technique has been suggested by the authors to address the main disadvantage of this technique, the long operative duration. The aim of this study was to compare these techniques in terms of efficacy, and clinical and radiological outcomes. Methods: We performed a retrospective, monocentric study. Two groups of patients were defined: One was treated with the standard flexible retrograde double nail technique and the other with the modified single nail technique. The demographic and fracture characteristics were similar in both groups and the postoperative immobilization with a simple sling for 2 weeks. We compared the surgical duration for the initial fixation and hardware removal procedures. The Quick Disabilities of the Arm, Shoulder, and Hand score, the secondary displacement at 1-week follow-up, the radiological union at 6-week follow-up, and the perioperative and short-term complications were also assessed for both groups. Results: The surgical duration of the initial fixation procedure was significantly shorter in single nail technique group (p = 0.005). The percentage of excellent Quick Disabilities of the Arm, Shoulder, and Hand score (0) was similar in the two groups (p = 0.98). No secondary displacement was reported for the double nail technique group. In only one patient from the single nail technique group, we detected a secondary displacement at the first week control which did not need reoperation. In both groups, fractures were healed on the 6-week radiologic control. No cases of infection, superficial skin irritation, neurological damage, or complications related to implant removal were reported in both groups. Conclusions: The single nail technique of fixation proximal humeral fractures in children addresses the disadvantage of long surgical times, described until today, with the double nail technique without compromising the excellent functional and radiological short-term outcomes. Level of evidence: level III.

Sleep promotes T-cell migration towards CCL19 via growth hormone and prolactin signaling in humans.

Sleep strongly supports the formation of adaptive immunity, e.g., after vaccination. However, the underlying mechanisms remain largely obscure. Here we show in healthy humans that sleep compared to nocturnal wakefulness specifically promotes the migration of various T-cell subsets towards the chemokine CCL19, which is essential for lymph-node homing and, thus, for the initiation and maintenance of adaptive immune responses. Migration towards the inflammatory chemokine CCL5 remained unaffected. Incubating the cells with plasma from sleeping participants likewise increased CCL19-directed migration, an effect that was dependent on growth hormone and prolactin signaling. These findings show that sleep selectively promotes the lymph node homing potential of T cells by increasing hormonal release, and thus reveal a causal mechanism underlying the supporting effect of sleep on adaptive immunity in humans.

Sleep shapes the associative structure underlying pattern completion in multielement event memory.

Sleep supports the consolidation of episodic memory. It is, however, a matter of ongoing debate how this effect is established, because, so far, it has been demonstrated almost exclusively for simple associations, which lack the complex associative structure of real-life events, typically comprising multiple elements with different association strengths. Because of this associative structure interlinking the individual elements, a partial cue (e.g., a single element) can recover an entire multielement event. This process, referred to as pattern completion, is a fundamental property of episodic memory. Yet, it is currently unknown how sleep affects the associative structure within multielement events and subsequent processes of pattern completion. Here, we investigated the effects of post-encoding sleep, compared with a period of nocturnal wakefulness (followed by a recovery night), on multielement associative structures in healthy humans using a verbal associative learning task including strongly, weakly, and not directly encoded associations. We demonstrate that sleep selectively benefits memory for weakly associated elements as well as for associations that were not directly encoded but not for strongly associated elements within a multielement event structure. Crucially, these effects were accompanied by a beneficial effect of sleep on the ability to recall multiple elements of an event based on a single common cue. In addition, retrieval performance was predicted by sleep spindle activity during post-encoding sleep. Together, these results indicate that sleep plays a fundamental role in shaping associative structures, thereby supporting pattern completion in complex multielement events.

Sleep consolidates stimulus-response learning.

Performing a motor response to a sensory stimulus creates a memory trace whose behavioral correlates are classically investigated in terms of repetition priming effects. Such stimulus-response learning entails two types of associations that are partly independent: (1) an association between the stimulus and the motor response and (2) an association between the stimulus and the classification task in which it is encountered. Here, we tested whether sleep supports long-lasting stimulus-response learning on a task requiring participants (1) for establishing stimulus-classification associations to classify presented objects along two different dimensions ("size" and "mechanical") and (2) as motor response (action) to respond with either the left or right index finger. Moreover, we examined whether strengthening of stimulus-classification associations is preferentially linked to nonrapid eye movement (non-REM) sleep and strengthening of stimulus-action associations to REM sleep. We tested 48 healthy volunteers in a between-subjects design comparing postlearning retention periods of nighttime sleep versus daytime wakefulness. At postretention testing, we found that sleep supports consolidation of both stimulus-action and stimulus-classification associations, as indicated by increased reaction times in "switch conditions"; that is, when, at test, the acutely instructed classification task and/or correct motor response for a given stimulus differed from that during original learning. Polysomnographic recordings revealed that both kinds of associations were correlated with non-REM spindle activity. Our results do not support the view of differential roles for non-REM and REM sleep in the consolidation of stimulus-classification and stimulus-action associations, respectively.

Pediatric phalanx fractures: A retrospective study and review of the literature.

Purpose: Conventional radiography is frequently performed in pediatric patients in whom finger fractures are suspected. However, until now, the rate of positive findings of finger radiographic examinations in pediatric patients is unknown. This study aimed to evaluate the number of positive findings in the standard radiographic examinations of finger injuries in pediatric patients in a Level 1 trauma center systematically. Methods: We conducted a retrospective study on all children 0-16 years old admitted for acute finger injury in the Emergency Department of a University Hospital during the first semester of 2019 and received a radiographic examination. Their demographic characteristics, fracture pattern, and treatment were then analyzed and interpreted. Results: Out of 478 finger injuries reviewed in this cohort, 160 X-rays revealed positive for a fracture giving a fracture rate of 33.5%. More than half of them (51.9%) occurred in the age group of adolescents (11-16 years). Among all finger fractures, only 3.8% of them treated surgically. Conclusion: In this study, a relevant amount of standard finger radiographs revealed a low fracture rate and a rare operative indication of 3.8%. Therefore, indications for X-rays should be reviewed properly and alternative procedures should be discussed. Clinical decision rules should be developed and the necessary pathways must be implemented to minimize radiation exposure, waiting time, and costs.Level of evidence: level IV.

Clinical and financial impacts of flexible intramedullary nailing in pediatric diaphyseal forearm fractures: A case-control study.

Purpose: Flexible intramedullary nailing is regularly applied for pediatric displaced unstable forearm fractures. When compared to closed reduction and casting (orthopedic treatment), flexible intramedullary nailing decreases malalignment, shortens immobilization time, and should decrease follow-up controls. Comparing flexible intramedullary nailing and orthopedic treatment in the clinical, radiological, and financial managements of these fractures was performed. Methods: Retrospective 5 years study of pediatric cases in two pediatric orthopedic university departments. Treatment method, post-operative course, and radiological follow-up were reviewed. Number of radiographs, follow-up controls, type and duration of immobilization, final bone angulation, and reported complications were compared. Extensive financial analysis was completed. Results: Of 73 girls and 168 boys included in the study, 150 were treated by flexible intramedullary nailing and 91 by orthopedic treatment. No difference was noted with regard to total number of radiographs (7.3 vs 7.2, respectively). Total number of follow-ups was 6.4 and 5.5, respectively. Malalignment occurred in two flexible intramedullary nailing and sixteen orthopedic treatments. The least expensive cost was ambulatory orthopedic treatment. Conclusion: Flexible intramedullary nailing treated children had similar numbers of radiographs or follow-up consultation, but less malunion when compared to orthopedic treatment. Orthopedic management was systematically cheaper than flexible intramedullary nailing. Unless post-operative management guidelines decreasing the number of radiographs and follow-ups are implemented, flexible intramedullary nailing will remain a costly procedure when compared to conventional orthopedic treatment. Level of evidence: level III case-control retrospective study.

Kingella kingae Spinal Infections in Children.

Nowadays, Kingella kingae is considered an important cause of primary spinal infections in children aged between 6 and 48 months. The presentation of the disease is often characterized by mild clinical features and a moderate biological inflammatory response, requiring a high index of suspicion. Performing magnetic resonance imaging (MRI) and obtaining an oropharyngeal specimen and subjecting it to a K. kingae-specific nucleic acid amplification test are recommended for its diagnosis. Most patients respond promptly to conservative treatment after administration of antibiotic therapy, which is prolonged for up to 3 months according to the individual clinical and biological response. Invasive surgical procedures are not required except for children who do not improve with antibiotic treatment, develop signs of cord compression, or if the presence of atypical microorganisms is suspected. Kingella kingae spinal infections usually run an indolent and benign clinical course, living no permanent sequelae.

Pilot Study and Preliminary Results of Biodegradable Intramedullary Nailing of Forearm Fractures in Children.

(1) Background: Diaphyseal forearm fractures are a common injury in children and adolescents. When operative treatment is needed, elastic stable intramedullary nailing (ESIN) is the most common surgical procedure. Although there is no clear evidence, hardware removal after fracture healing is performed in many patients. Often, the primary minimal invasive incision needs to be widened during implant removal. In order to decrease the burden of care of pediatric fractures, significant efforts were made to develop biodegradable implants, which make hardware removal unnecessary. Our study will conduct an observational trial on the clinical use of the Activa IM-Nail™ in forearm fractures in children between 3 and 13 years of age. The objective of this trial is to evaluate the risks and benefits of the Activa IM-Nail™. Among other objectives, the rate of refracture will be determined. (2) Methods: An international Europe-based, multicenter, prospective, single-arm, open-label study will be performed to ascertain the rate of refracture and to determine the subjective benefits of Activa IM-Nail™ for patients, parents and other caregivers. The study will include clinical follow-up including early post-operative complication, radiographs until bony healing and an additional follow-up after 1 year. At this stage, preliminary results and early complications on 76 patients are analyzed in this study and presented. (3) Results: As of April 2022, 76 patients were enrolled as per study protocol. There were 31 girls (40.8%) and 45 boys (59.2%). The mean age at the time of inclusion was 8.9 years (±2.4 years). The mean operation time was 58.9 ± 22.9 min (range, 15-119 min). The mean follow-up time was 8.9 ± 5.1 months (range, 0.2-18.6). Up to now, one refracture has occurred in one child falling from a height of about one meter 7 months after index surgery (1/76; 1.3%). (4) Conclusion: The research project assesses the safety and effectiveness of Activa IM-Nails™ as part of the surgical treatment of dislocated forearm fractures in children in the context of a PMCF study. The use of Activa IM-Nails™ with regard to various objectives, including postoperative complications and refracture rate, seems to be equal to the standard titan ESIN procedure compared to the literature. Preliminary results are encouraging and are made available.

Determining the development stage of the ossification centers around the elbow may aid in deciding whether to use ESIN or not in adolescents' forearm shaft fractures.

Background and purpose - Elastic stable intramedullary nailing (ESIN) is the preferred method of operative stabilization of unstable pediatric forearm shaft fractures. However, the decision whether to use ESIN or open reduction and internal fixation (ORIF) in older children or teenagers is not always straightforward. We hypothesized that the development stage of the elbow would aid in evaluating the eligibility of the patient for ESIN.Patients and methods - All eligible children, aged <16 years who were treated with ESIN in Oulu University Hospital, during 2010-2019 were included (N = 70). The development stages of 4 ossification centers were assessed according to the Sauvegrain and Diméglio scoring. The proportion of impaired union vs. union was analyzed according to bone maturity, by using the optimal cutoff-points determined with receiver operating characteristics (ROC).Results - Development stage ≥ 6 in the olecranon was associated with impaired union in 20% of patients, compared with none in stages 1-5 (95% CI of difference 8% to 24%). Trochlear ossification center ≥ 4 was associated with impaired union in 17% of patients (CI of difference 7% to 36%) and lateral condyle ≥ 6 in 13% of patients (CI of difference 3.4% to 30%). Proximal radial head ≥ 5.5 was associated with impaired union in 18% of patients (CI of difference 7% to 39%).Interpretation - Recognizing the rectangular or fused olecranon ossification center, referring to stage ≥ 6, was in particular associated with impaired fracture healing. This finding may aid clinicians to consider between ESIN and plating, when treating forearm shaft fracture of an older child or teenager.

A Single Retrograde Intramedullary Nail Technique for Treatment of Displaced Proximal Humeral Fractures in Children: Case Series and Review of the Literature.

Displaced proximal humeral fractures in older children with low remodeling potential need to be reduced and fixed. There are many options for stabilization, including external fixation, rigid internal fixation with screws and plates, percutaneous pinning, and flexible intramedullary nailing. The use of 2 flexible retrograde nails, originated at the University of Nancy, France, became the most popular technique in Europe. The aim of this study was to describe and assess a modified, single retrograde nail technique to treat fractures of the proximal part of the humerus. METHODS: We performed a retrospective monocentric study. From June 2016 to May 2019, a modified retrograde nail technique with 1 prebent nail was used for the management of 21 consecutive children with a closed displaced proximal humeral fracture. Demographic and surgical data were collected. The surgical technique is similar to the classic elastic stable intramedullary nailing, but only 1 nail is used. The average surgical time and perioperative complications were used as criteria for the feasibility of this technique. Radiographs were obtained preoperatively; at 1, 4, and 6 weeks postoperatively; and after implant removal at an average of 4.2 months postoperatively. The clinical outcomes were assessed on the basis of the shoulder range of motion documented in the medical records and by using the French edition of the QuickDASH (shortened version of the Disabilities of the Arm, Shoulder and Hand [DASH] questionnaire) evaluation scale at the time of implant removal. RESULTS: Nineteen patients with a mean age of 12.6 years and a mean follow-up of 6 months were included in the study. The mean surgical time was 49 minutes. The single intramedullary nail technique provided a satisfactory reduction of all fractures. No perioperative complication occurred. In 1 case, partial loss of reduction was observed on the first-week control radiograph. All patients had a healed fracture, no deficits, excellent results according to the QuickDASH score, a normal range of motion, and excellent strength of the shoulder joint at the time of implant removal (at a mean of 4.2 months). CONCLUSIONS: The current study confirms the feasibility and efficacy of the single retrograde intramedullary nail technique to treat displaced proximal humeral fractures in children. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Occipital sleep spindles predict sequence learning in a visuo-motor task.

STUDY OBJECTIVES: The brain appears to use internal models to successfully interact with its environment via active predictions of future events. Both internal models and the predictions derived from them are based on previous experience. However, it remains unclear how previously encoded information is maintained to support this function, especially in the visual domain. In the present study, we hypothesized that sleep consolidates newly encoded spatio-temporal regularities to improve predictions afterwards. METHODS: We tested this hypothesis using a novel sequence-learning paradigm that aimed to dissociate perceptual from motor learning. We recorded behavioral performance and high-density electroencephalography (EEG) in male human participants during initial training and during testing two days later, following an experimental night of sleep (n = 16, including high-density EEG recordings) or wakefulness (n = 17). RESULTS: Our results show sleep-dependent behavioral improvements correlated with sleep-spindle activity specifically over occipital cortices. Moreover, event-related potential (ERP) responses indicate a shift of attention away from predictable to unpredictable sequences after sleep, consistent with enhanced automaticity in the processing of predictable sequences. CONCLUSIONS: These findings suggest a sleep-dependent improvement in the prediction of visual sequences, likely related to visual cortex reactivation during sleep spindles. Considering that controls in our experiments did not fully exclude oculomotor contributions, future studies will need to address the extent to which these effects depend on purely perceptual versus oculomotor sequence learning.

Association Between Objectively Assessed Sleep and Depressive Symptoms During Pregnancy and Post-partum.

INTRODUCTION: Sleep problems are common in pregnancy but many studies have relied only on self-reported sleep measures. We studied the association between objectively measured sleep and peripartum depressive symptoms in pregnant women. MATERIAL AND METHODS: Sleep was assessed using Actiwatch accelerometers in a sample of 163 pregnant women in the late first (weeks 11-15) or early second trimester (weeks 16-19). Depressive symptoms were assessed in gestational weeks 17, 32 and at 6 weeks post-partum using the Edinburgh Postnatal Depression Scale (EPDS). Multiple linear regression and logistic regression analyses, adjusting for age, BMI, pre-pregnancy smoking, ongoing mental health problems, trimester and season of sleep assessment were carried out to test the association between sleep and depression. Sleep was measured by total sleep time and sleep efficiency, whereas depression was indicated by depressive symptoms and depression caseness. Results are presented as unstandardized beta (B) coefficients or adjusted odds ratios (AOR) and 95% confidence intervals (CI). RESULTS: Total sleep time ranged from 3 to 9 h (mean 7.1, SD 0.9) and average sleep efficiency was 83% (SD 6.0). Women with the shortest total sleep time, i.e., in the lowest quartile (<6.66 h), reported higher depressive symptoms during pregnancy (week 17, B = 2.13, 95% CI 0.30-3.96; week 32, B = 1.70, 95% CI 0.03-3.37) but not post-partum. Their probability to screen positive for depression in gestational week 17 was increased more than 3-fold (AOR = 3.46, 95% CI 1.07-11.51) but unchanged with regards to gestational week 32 or 6 weeks post-partum. Sleep efficiency was not associated with depressive symptoms at any stage of pregnancy or post-partum. DISCUSSION: In one of the few studies to use objective sleep measures to date, mental health of pregnant women appeared to be affected by shortened sleep, with total sleep time being negatively associated with depressive symptoms in the early second and third trimester. This finding highlights the relevance of identifying and treating sleep impairments in pregnant women early during antenatal care to reduce the risk of concomitant depression.

Patella Osteomyelitis Mimicking Sinding-Larsen and Johansson Apophysitis: A Pitfall Not to Miss.

BACKGROUND: Diagnosis of bony infection remains difficult during childhood. Osteomyelitis of the patella (OMP) is rare and produces few symptoms and no fever. A high level of suspicion is needed to avoid missing this uncommon type of bone infection. METHODS: /. RESULTS: We report an acute osteomyelitis of the patella treated by joint and patella puncture aspiration followed by antibiotics in a 12-year-old healthy boy. Clinical and radiological findings, orthopedic follow-up, and clinical outcome are presented. CONCLUSION: Making a diagnosis of acute osteomyelitis of the patella can be challenging especially in the pediatric population, as it produces few specific symptoms with mostly nonspecific biologic anomalies. The paucity in specific signs and symptoms, accompanied by the rare occurrence, often leads to incorrect initial diagnosis, such as overuse injury or apophysitis. Clinical examination with high suspicion for patella infection is key. Radiological exams including MRI are the main components of the adequate imaging studies. Computed tomography may be an excellent addendum to better visualize any bony lesion within the patella. Bone aspiration or biopsy is essential to confirm the diagnosis and offers a first step in the treatment of this infection, which can then be successfully treated with a normal course of antibiotics.

The Association of Metal Frame Construct of ESIN and radiographic bone healing of pediatric forearm fractures.

INTRODUCTION: The gold-standard surgical procedure of both-bone forearm shaft fracture repair is elastic stable intramedullary nailing (ESIN). Disadvantages effects of ESIN have suggested to be a consequence of inappropriate surgical techniques, while recommendations are not always followed. The purpose of the study was to analyze the effect of inadequate metal frame construct on impaired fracture healing, refracture and changing alignment. MATERIALS AND METHODS: It is a population-based study including all consecutive patients, aged less than 16 years, who had been treated for forearm shaft fracture by ESIN during the ten-year period 2009-2018. Altogether 71 patients were included. Non-union, delayed union, and re-fracture during the following 12 months were taken as the main outcome, while inferior metal frame construct of ESIN and the surgical technique characteristics were taken the explanatory factors. Radiographic loss of reduction was a secondary outcome and a change >5° in alignment at any postoperative follow-up exam was recognized. RESULTS: Two out of 71 fractures (3%) failed to unite, and ossifying operation was needed. Five cases (7%) showed delayed bone healing, but they ossified in five months without any intervention. These seven patients (10%) had been treated more often with larger nails (> 0.7x MCD) (p = 0.027) and by open reduction (p = 0.02), compared with thinner nails and closed reduction, respectively. Two (3%) patients had a second fracture; however, they happened 2 years after the initial injury. Other surgery or fracture related factors didn't associate with impaired ossifying. Regarding the secondary outcome, altogether 24 (35%) of the analyzed 67 patients showed >5° change in alignment during the postoperative follow-up but only one patient had clinically significant instability that required re-reduction. The alignment changed more usually in distal-third fractures, compared with middle or proximal third fractures (p = 0.019). CONCLUSIONS: ESIN resulted in good radiographic bone healing in the vast majority (90%) of the patients and completely perfect metal frame construct was not required.

[Ankle sprain in youth athlete]. / Entorse de la cheville chez le jeune sportif.

Lateral ankle sprain is the most frequent musculoskeletal injury in the young athlete. Myths, dogma and common belief are regularly encountered when discussing this injury, for which the scientific literature does not prevail yet. In the youth, the growing skeleton further influences the diagnosis and therapeutic processes, as well as the healing potential. For the athlete, a fast recovery and return to sports without recurrence are a priority. In this specific context, an integrated management of the ankle sprain in the young athlete must be based on an adequate diagnosis, a sound knowledge of pediatrics pitfalls and peer-reviewed physiotherapy recommendations and consensus statements.

Lésion musculosquelettique la plus fréquente chez le jeune sportif, l'entorse de la cheville n'en reste pas moins un sujet médical où foisonnent les idées reçues, les dogmes et les mythes que la science a du mal à faire disparaître. Lorsqu'elle affecte un jeune, les pièges du squelette en croissance et le potentiel de guérison sont des éléments supplémentaires influençant le processus diagnostique et thérapeutique. Chez le sportif, le retour rapide à l'entraînement en évitant tout risque de récidive est une priorité. Dans ce contexte, la prise en charge intégrée de l'entorse de la cheville chez le jeune sportif doit être basée sur un bon diagnostic, une connaissance des pièges pédiatriques et des recommandations physiothérapeutiques basées sur l'évidence et les avis de consensus.

Paediatric musculoskeletal infections with Panton-Valentine leucocidin.

AIMS OF THE STUDY: Paediatric musculoskeletal infections by Panton-Valentine leucocidin (PVL)-producing Staphylococcus aureus constitute a rare, but highly critical event. They are characterised by a rapid course of marked inflammation, worsening under conservative therapy and a high rate of recurrence. This study aimed to illustrate the importance of paediatric PVL-producing S. aureus musculoskeletal infections in western Switzerland. METHODS: Case records, clinical parameters and biological assessments of children with musculoskeletal infections due to PVL-producing S. aureus who attended the University Hospitals of Lausanne and Geneva from 2008 to 2016 were studied retrospectively. RESULTS: Of the nine cases (seven male), four presented with haematogenous acute osteomyelitis, two with septic arthritis, and three with skin and soft tissue infections. Laboratory analysis revealed mean values for white blood cell count of 12,700/mm3, C-reactive protein (CRP) 171mg/l, erythrocyte sedimentation rate (ESR) 62 mm/h and platelet count 241,000/mm3. Notably, fever and laboratory values were higher for osteoarticular infections. PVL was produced by methicillin-sensitive S. aureus (MSSA) in eight cases and by community-acquired methicillin-resistant S. aureus (CA-MRSA) in one case. PVL was identified in blood cultures (six cases), operative samples (seven cases) and an oral swab (one case). Treatment relied on surgical procedures, endorsed by two-agent antimicrobial therapy for up to 9 weeks. Complications included recurrent infections (five cases), pathological fracture (one case) and growth arrest (two cases), as well as an important psychological impact (one case). CONCLUSION: The results of this study highlight the low prevalence of PVL-producing S. aureus musculoskeletal infections in the paediatric population in our region. Nevertheless, given the importance of complications, the recurrence rate and the duration of treatment, clinicians caring for children need to be especially well versed with the peculiarity of this entity. Retrospective case series. LEVEL OF EVIDENCE: IV.

Sleep Strengthens Predictive Sequence Coding.

Predictive-coding theories assume that perception and action are based on internal models derived from previous experience. Such internal models require selection and consolidation to be stored over time. Sleep is known to support memory consolidation. We hypothesized that sleep supports both consolidation and abstraction of an internal task model that is subsequently used to predict upcoming stimuli. Human subjects (of either sex) were trained on deterministic visual sequences and tested with interleaved deviant stimuli after retention intervals of sleep or wakefulness. Adopting a predictive-coding approach, we found increased prediction strength after sleep, as expressed by increased error rates to deviant stimuli, but fewer errors for the immediately following standard stimuli. Sleep likewise enhanced the formation of an abstract sequence model, independent of the temporal context during training. Moreover, sleep increased confidence for sequence knowledge, reflecting enhanced metacognitive access to the model. Our results suggest that sleep supports the formation of internal models which can be used to predict upcoming events in different contexts.SIGNIFICANCE STATEMENT To efficiently interact with the ever-changing world, we predict upcoming events based on similar previous experiences. Sleep is known to benefit memory consolidation. However, it is not clear whether sleep specifically supports the transformation of past experience into predictions of future events. Here, we find that, when human subjects sleep after learning a sequence of predictable visual events, they make better predictions about upcoming events compared with subjects who stayed awake for an equivalent period of time. In addition, sleep supports the transfer of such knowledge between different temporal contexts (i.e., when sequences unfold at different speeds). Thus, sleep supports perception and action by enhancing the predictive utility of previous experiences.

The rod signaling pathway in marsupial retinae.

The retinal rod pathway, featuring dedicated rod bipolar cells (RBCs) and AII amacrine cells, has been intensely studied in placental mammals. Here, we analyzed the rod pathway in a nocturnal marsupial, the South American opossum Monodelphis domestica to elucidate whether marsupials have a similar rod pathway. The retina was dominated by rods with densities of 338,000-413,000/mm². Immunohistochemistry for the RBC-specific marker protein kinase Cα (PKCα) and the AII cell marker calretinin revealed the presence of both cell types with their typical morphology. This is the first demonstration of RBCs in a marsupial and of the integration of RBCs and AII cells in the rod signaling pathway. Electron microscopy showed invaginating synaptic contacts of the PKCα-immunoreactive bipolar cells with rods; light microscopic co-immunolabeling for the synaptic ribbon marker CtBP2 confirmed dominant rod contacts. The RBC axon terminals were mostly located in the innermost stratum S5 of the inner plexiform layer (IPL), but had additional side branches and synaptic varicosities in strata S3 and S4, with S3-S5 belonging to the presumed functional ON sublayer of the IPL, as shown by immunolabeling for the ON bipolar cell marker Gγ13. Triple-immunolabeling for PKCα, calretinin and CtBP2 demonstrated RBC synapses onto AII cells. These features conform to the pattern seen in placental mammals, indicating a basically similar rod pathway in M. domestica. The density range of RBCs was 9,900-16,600/mm2, that of AII cells was 1,500-3,260/mm2. The numerical convergence (density ratio) of 146-156 rods to 4.7-6.0 RBCs to 1 AII cell is within the broad range found among placental mammals. For comparison, we collected data for the Australian nocturnal dunnart Sminthopsis crassicaudata, and found it to be similar to M. domestica, with rod-contacting PKCα-immunoreactive bipolar cells that had axon terminals also stratifying in IPL strata S3-S5.