Sleep-mediated memory consolidation depends on the level of integration at encoding.

There is robust evidence that sleep facilitates declarative memory consolidation. Integration of newly acquired memories into existing neocortical knowledge networks has been proposed to underlie this effect. Here, we test whether sleep affects memory retention for word-picture associations differently when it was learned explicitly or using a fast mapping strategy. Fast mapping is an incidental form of learning that references new information to existing knowledge and possibly allows neocortical integration already during encoding. If the integration of information into neocortical networks is a main function of sleep-dependent memory consolidation, material learned via fast mapping should therefore benefit less from sleep. Supporting this idea, we find that sleep has a protective effect on explicitly learned associations. In contrast, memory for associations learned by fast mapping does not benefit from sleep and remains stable regardless of whether sleep or wakefulness follows learning. Our results thus indicate that the need for sleep-mediated consolidation depends on the strategy used for learning and might thus be related to the level of integration of newly acquired memory achieved during encoding.

Genetic adaptation to levels of dietary selenium in recent human history.

As humans migrated around the world, they came to inhabit environments that differ widely in the soil levels of certain micronutrients, including selenium (Se). Coupled with cultural variation in dietary practices, these migrations have led to a wide range of Se intake levels in populations around the world. Both excess and deficiency of Se in the diet can have adverse health consequences in humans, with severe Se deficiency resulting in diseases of the bone and heart. Se is required by humans mainly due to its function in selenoproteins, which contain the amino acid selenocysteine as one of their constituent residues. To understand the evolution of the use of this micronutrient in humans, we surveyed the patterns of polymorphism in all selenoprotein genes and genes involved in their regulation in 50 human populations. We find that single nucleotide polymorphisms from populations in Asia, particularly in populations living in the extreme Se-deficient regions of China, have experienced concerted shifts in their allele frequencies. Such differentiation in allele frequencies across genes is not observed in other regions of the world and is not expected under neutral evolution, being better explained by the action of recent positive selection. Thus, recent changes in the use and regulation of Se may harbor the genetic adaptations that helped humans inhabit environments that do not provide adequate levels of Se in the diet.

Pancreas divisum: a differentiated surgical approach in symptomatic patients.

BACKGROUND: Some patients with pancreas divisum (PD) develop symptoms of recurrent pancreatitis. This is probably caused by insufficient drainage of the pancreatic duct. We report the results of our follow-up of patients who underwent surgery for symptomatic pancreas divisum according to an individualized surgical approach. METHODS: Between October 2001 and April 2009, 28 patients with symptomatic pancreas divisum were operated at the University Hospital of Heidelberg. According to the localization and type of morphological changes of the pancreas, patients received a reinsertion of the papilla (SP; n=11), duodenum-preserving pancreatic head resection (DPPHR; n=10), pylorus-preserving Whipple (ppWhipple; n=4), or other pancreatic resections (n=3). Hospitalization, morbidity, mortality, pain course, and patient satisfaction were analyzed. RESULTS: Before surgery, patients received a median of three endoscopic interventions and were hospitalized for 77 days. The median postoperative follow-up was 4.1 years. Surgical morbidity was 11% and mortality 0%. We performed an SP when the pancreas was soft (n=10). When the pancreas was inflammatory altered, a DPPHR was performed in ten, ppW in four, segmental resection in two, and SP and pancreatic left resection in one case. A redo operation for persisting symptoms was needed in six patients (3 soft and 3 altered pancreas). Compared with the preoperative situation, pain was significantly reduced in the follow-up (median Visual Analogue Scale 0 vs. 10). Ninety-six percent of patients were without symptoms during the follow-up. CONCLUSIONS: The individualized surgical approach for patients with symptomatic PD achieves significant reduction of pain in all patients. Reinsertions of the papilla should be performed as a first surgical intervention in patients with a soft pancreas when symptoms persist despite adequate endoscopic treatment. DPPHR should be performed when fibrotic alterations of the pancreas are present.