Novel Mouse Model Reveals Distinct Activity-Dependent and –Independent Contributions to Synapse Development

The balanced action of both pre- and postsynaptic organizers regulates the formation of neuromuscular junctions (NMJ). The precise mechanisms that control the regional specialization of acetylcholine receptor (AChR) aggregation, guide ingrowing axons and contribute to correct synaptic patterning are unknown. Synaptic activity is of central importance and to understand synaptogenesis, it is necessary to distinguish between activity-dependent and activity-independent processes. By engineering a mutated fetal AChR subunit, we used homologous recombination to develop a mouse line that expresses AChR with massively reduced open probability during embryonic development. Through histological and immunochemical methods as well as electrophysiological techniques, we observed that endplate anatomy and distribution are severely aberrant and innervation patterns are completely disrupted. Nonetheless, in the absence of activity AChRs form postsynaptic specializations attracting motor axons and permitting generation of multiple nerve/muscle contacts on individual fibers. This process is not restricted to a specialized central zone of the diaphragm and proceeds throughout embryonic development. Phenotypes can be attributed to separate activity-dependent and -independent pathways. The correct patterning of synaptic connections, prevention of multiple contacts and control of nerve growth require AChR-mediated activity. In contrast, myotube survival and acetylcholine-mediated dispersal of AChRs are maintained even in the absence of AChR-mediated activity. Because mouse models in which acetylcholine is entirely absent do not display similar effects, we conclude that acetylcholine binding to the AChR initiates activity-dependent and activity-independent pathways whereby the AChR modulates formation of the NMJ

Adaptive teaching: Conceptual reflections

Der vorliegende Beitrag betrachtet den in Politik und Praxis populären Begriff der individuellen Förderung. Dazu wird zunächst erörtert, in welchen Kontexten und in welcher Form der Begriff bislang verwendet wurde. Anschließend werden im wissenschaftlichen Diskurs etablierte verwandte Konzepte von individueller Förderung und Erkenntnisse aus der kognitiven Lehr-Lern-Forschung und der Unterrichtsforschung dargestellt. Darauf aufbauend wird vorgeschlagen, individuelle Förderung im Sinne einer tiefgreifenden Gesamtunterrichtsstrategie zu verstehen, bei der die Lehrkraft den einzelnen Schülerinnen und Schülern ein an ihre spezifischen Lernvoraussetzungen angepasstes Lernangebot macht und das Ziel einer kontinuierlich zunehmenden Verantwortungsübernahme der Schülerinnen und Schüler für ihren eigenen Lernprozess verfolgt. Abschließend werden Implikationen dieser Konzeption für die Schulpraxis und die Bildungsforschung diskutiert. (DIPF/Orig.)The present paper deals with the German concept "Individuelle Förderung", which has been widely used in both policy and practice in recent years and may best be translated into "adaptive teaching" or "individualized instruction". The paper first addresses the contexts and ways in which the term has been used. Several related concepts used in educational research and findings from research on learning and instruction are presented. Using these insights, the author proposes to conceptualize "Individuelle Förderung" as an overarching teaching concept in which teachers adapt their instruction to each student\u27s needs and aim to increase students\u27 responsibility for their own learning process. The paper closes with implications of this conceptualization for practice and research. (DIPF/Orig.