Disruption of NREM sleep and sleep-related spatial memory consolidation in mice lacking adult hippocampal neurogenesis.

Cellular plasticity at the structural level and sleep at the behavioural level are both essential for memory formation. The link between the two is not well understood. A functional connection between adult neurogenesis and hippocampus-dependent memory consolidation during NREM sleep has been hypothesized but not experimentally shown. Here, we present evidence that during a three-day learning session in the Morris water maze task a genetic knockout model of adult neurogenesis (Cyclin D2-/-) showed changes in sleep macro- and microstructure. Sleep EEG analyses revealed a lower total sleep time and NREM fraction in Cyclin D2-/- mice as well as an impairment of sleep specific neuronal oscillations that are associated with memory consolidation. Better performance in the memory task was associated with specific sleep parameters in wild-type, but not in Cyclin D2-/- mice. In wild-type animals the number of proliferating cells correlated with the amount of NREM sleep. The lack of adult neurogenesis led to changes in sleep architecture and oscillations that represent the dialog between hippocampus and neocortex during sleep. We suggest that adult neurogenesis-as a key event of hippocampal plasticity-might play an important role for sleep-dependent memory consolidation and modulates learning-induced changes of sleep macro- and microstructure.

Impact of aerobic exercise training during chemotherapy on cancer related cognitive impairments in patients suffering from acute myeloid leukemia or myelodysplastic syndrome - Study protocol of a randomized placebo-controlled trial.

Cancer related cognitive impairments (CRCI) are frequently reported by patients prior to, during and after medical treatment. Although this cognitive decline severely affects patients' quality of life, little is known about effective treatments. Exercise programs represent a promising supportive strategy in this field. However, evidence is sparse and existing studies display methodological limitations. In the planned study, 83 men and women newly diagnosed with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) will be randomized into one of three treatment groups. During 4weeks of induction chemotherapy with Anthracycline and Cytarabin patients allocated to exercise group will cycle 3×/week for 30min at moderate to vigorous intensity on an ergometer. Patients allocated to placebo group will receive a supervised myofascial release training (3×/week, approx. 30min) and patients at control group will get usual care. As primary endpoints a cognitive test battery will be conducted measuring performances depending on verbal/spatial memory and executive functioning. Secondary endpoints will be self-perceived cognitive functioning, as well as neurotrophic and inflammatory serum markers. All assessments will be conducted immediately after hospitalization and before chemotherapy is commenced, immediately before discharge of hospital after 4-5weeks as well as before continuing medical treatment 3-4weeks after discharge. This will be the first study investigating the impact of an aerobic exercise training on CRCI in AML/MDS patients. We hope that the study design and the state-of-the-art assessments will help to increase knowledge about CRCI in general and exercise as potential treatment option in this under investigated population.

Not all water mazes are created equal: cyclin D2 knockout mice with constitutively suppressed adult hippocampal neurogenesis do show specific spatial learning deficits.

Studies using the Morris water maze to assess hippocampal function in animals, in which adult hippocampal neurogenesis had been suppressed, have yielded seemingly contradictory results. Cyclin D2 knockout (Ccnd2(-/-)) mice, for example, have constitutively suppressed adult hippocampal neurogenesis but had no overt phenotype in the water maze. In other paradigms, however, ablation of adult neurogenesis was associated with specific deficits in the water maze. Therefore, we hypothesized that the neurogenesis-related phenotype might also become detectable in Ccnd2(-/-) mice, if we used the exact setup and protocol that in our previous study had revealed deficits in mice with suppressed adult neurogenesis. Ccnd2(-/-) mice indeed learned the task and developed a normal preference for the goal quadrant, but were significantly less precise for the exact goal position and were slower in acquiring efficient and spatially more precise search strategies. Upon goal reversal (when the hidden platform was moved to a new position) Ccnd2(-/-) mice showed increased perseverance at the former platform location, implying that they were less flexible in updating the previously learned information. Both with respect to adult neurogenesis and behavioral performance, Ccnd2(+/-) mice ranged between wild types and knockouts. Importantly, hippocampus-dependent learning was not generally impaired by the mutation, but specifically functional aspects relying on precise and flexible encoding were affected. Whether ablation of adult neurogenesis causes a specific behavioral phenotype thus also depends on the actual task demands. The test parameters appear to be important variables influencing whether a task can pick up a contribution of adult neurogenesis to test performance.