Synaptic depression and short-term habituation are located in the sensory part of the mammalian startle pathway

BACKGROUND: Short-term habituation of the startle response represents an elementary form of learning in mammals. The underlying mechanism is located within the primary startle pathway, presumably at sensory synapses on giant neurons in the caudal pontine reticular nucleus (PnC). Short trains of action potentials in sensory afferent fibers induce depression of synaptic responses in PnC giant neurons, a phenomenon that has been proposed to be the cellular correlate for short-term habituation. We address here the question whether both this synaptic depression and the short-term habituation of the startle response are localized at the presynaptic terminals of sensory afferents. If this is confirmed, it would imply that these processes take place prior to multimodal signal integration, rather than occurring at postsynaptic sites on PnC giant neurons that directly drive motor neurons. RESULTS: Patch-clamp recordings in vitro were combined with behavioral experiments; synaptic depression was specific for the input pathway stimulated and did not affect signals elicited by other sensory afferents. Concordant with this, short-term habituation of the acoustic startle response in behavioral experiments did not influence tactile startle response amplitudes and vice versa. Further electrophysiological analysis showed that the passive properties of the postsynaptic neuron were unchanged but revealed some alterations in short-term plasticity during depression. Moreover, depression was induced only by trains of presynaptic action potentials and not by single pulses. There was no evidence for transmitter receptor desensitization. In summary, the data indicates that the synaptic depression mechanism is located presynaptically. CONCLUSION: Our electrophysiological and behavioral data strongly indicate that synaptic depression in the PnC as well as short-term habituation are located in the sensory part of the startle pathway, namely at the axon terminals of sensory afferents in the PnC. Our results further corroborate the link between synaptic depression and short-term habituation of the startle response

Longterm-habituation of the startle response in mice is stimulus modality, but not context specific

In mice, the specificity of longterm-habituation (LTH) of startle was tested in two experiments. In two strains of mice (C57Bl/6 and C3H) there was pronounced LTH over 10 days of acoustic stimulation in two different contexts of startle measurement. (We found LTH to be greater after stimulation with 14 kHz sine stimuli compared to noise or tactile stimuli). A change of context showed LTH to be independent of context, i.e., startle LTH in mice is a non-associative learning process. In the second experiment, 9 days of acoustic or tactile stimulation were given to C57B/6 mice. Both stimulus modalities produced LTH. When on the 10th day stimuli of the other modality were given, in both cases the long term habituated group showed no lower startle amplitude than a non-stimulated control group. This indicates LTH is stimulus-modality specific. Altogether, our results show that in mice—very similar to rats—LTH of startle is stimulus modality, but not context specific. In addition we found two indications that the LTH action site is on the sensory branch of the startle circuit

Synaptic depression and short-term habituation are located in the sensory part of the mammalian startle pathway

Abstract Background Short-term habituation of the startle response represents an elementary form of learning in mammals. The underlying mechanism is located within the primary startle pathway, presumably at sensory synapses on giant neurons in the caudal pontine reticular nucleus (PnC). Short trains of action potentials in sensory afferent fibers induce depression of synaptic responses in PnC giant neurons, a phenomenon that has been proposed to be the cellular correlate for short-term habituation. We address here the question whether both this synaptic depression and the short-term habituation of the startle response are localized at the presynaptic terminals of sensory afferents. If this is confirmed, it would imply that these processes take place prior to multimodal signal integration, rather than occurring at postsynaptic sites on PnC giant neurons that directly drive motor neurons. Results Patch-clamp recordings in vitro were combined with behavioral experiments; synaptic depression was specific for the input pathway stimulated and did not affect signals elicited by other sensory afferents. Concordant with this, short-term habituation of the acoustic startle response in behavioral experiments did not influence tactile startle response amplitudes and vice versa. Further electrophysiological analysis showed that the passive properties of the postsynaptic neuron were unchanged but revealed some alterations in short-term plasticity during depression. Moreover, depression was induced only by trains of presynaptic action potentials and not by single pulses. There was no evidence for transmitter receptor desensitization. In summary, the data indicates that the synaptic depression mechanism is located presynaptically. Conclusion Our electrophysiological and behavioral data strongly indicate that synaptic depression in the PnC as well as short-term habituation are located in the sensory part of the startle pathway, namely at the axon terminals of sensory afferents in the PnC. Our results further corroborate the link between synaptic depression and short-term habituation of the startle response.</p

Academic education of midwives in Germany (part 1): Requirements for bachelor of science programmes in midwifery education. Position paper of the Midwifery Science Committee (AHW) in the DACH Association for Medical Education (GMA)

The current situation in Germany is characterised by significant differences between the two types of higher education institutions offering bachelor's degree programmes in midwifery at both universities of applied sciences and universities. These differences are noticeable in admission procedures, resource allocation, content focus and competence assessment at the respective institutions, which in turn result in heterogeneous study experiences. This article highlights the challenges currently facing bachelor degree programmes and the academic qualification of midwives, and identifies future requirements for the development of degree programmes in theory and practice as well as theory-practice transfer, and assessment formats. Furthermore, this article covers the content-related and structural-organisational requirements to develop in-depth academic skills grounded in theory teaching, the facilitation of clinical placements at an academic level, the training of qualified practical instructors and the development of applicable competence-based assessment formats, especially for the state exam.The development of a standardised, high-quality academic education for midwives in Germany requires networking of the different academic sites/locations to exchange experiences in teaching/learning and assessment formats. Furthermore, it can facilitate the development of a standardised competence-oriented model and core curriculum as well as the definition of quality criteria and standards for study programmes of midwifery science. The Midwifery Science Committee (AHW) in the DACH Assoviation for Medical Education (GMA) offers an optimal platform for cooperation between the different universities. The existing challenges for the further professional development of midwives can only be overcome by collaboration and pooled expertise

Academic education of midwives in Germany (part 2): Opportunities and challenges for the further development of the profession of midwifery. Position paper of the Midwifery Science Committee (AHW) in the DACH Association for Medical Education (GMA)

The objective of academic training is to prepare midwives as independent healthcare professionals to make a substantial contribution to the healthcare of women in their reproductive years as well as to the health of their children and families. This article therefore describes the professional and educational requirements derived from the legal midwifery competencies within the new midwifery act. Furthermore, it identifies the conditions that need to be established to enable midwives in Germany to practise to their full scope in compliance with statutory responsibilities. Educational science, academic efforts, policymaking and accompanying research should work in synergy. This in turn enables midwives to achieve the maximum scope of their skills, with the objective of promoting physiological pregnancies and births. Consequently, it can strengthen early parenthood in alignment with the national health objectives of “health around childbirth”.The academisation of the midwifery profession presents a profound opportunity for professional development in Germany. It is essential that midwives receive training based on the principles of educational science and care structures that are yet to be developed. This can enable them to perform within the wide range of their professional tasks to the highest standards, thereby ensuring the optimal care of their clients. Moreover, there is a chance to implement sustainable improvements in healthcare provision for women and their families during the reproductive phase and the period of parenthood in Germany