Steroid Hormone Interaction with Dendritic Spines: Implications for Neuropsychiatric Disease.

Dendritic spines, key sites for neural plasticity, are influenced by gonadal steroids. In this chapter, we review the effects of gonadal steroids on dendritic spine density in areas important to cognitive function, the hippocampus, and prefrontal cortex. Most of these animal model studies investigated the effects of estrogen in females, but we also include more recent data on androgen effects in both males and females. The underlying genomic and non-genomic mechanisms related to gonadal steroid-induced spinogenesis are also reviewed. Subsequently, we discuss possible reasons for the observed sex differences in many neuropsychiatric diseases, which appear to be caused, in part, by aberrant synaptic connections that may involve dendritic spine pathology. Overall, knowledge concerning the regulation of dendritic spines by gonadal hormones has grown since the initial discoveries in the 1990s, and current research points to a potential role for aberrant spine functioning in many neuropsychiatric disorders.

Teaching and Learning Neuroanatomy with Gestures: A Description of Two Simple Hand Models.

Neuroanatomy ranks highly among the most difficult topics to master in medical school. We describe two gesture-based techniques aimed at simplifying the anatomy of two complex intracranial nervous structures: the trigeminal nerve and the cerebral fornix.

Consolidation Carnival: A Case-Based Approach to Reviewing Musculoskeletal Anatomy in an Undergraduate Medical Curriculum.

Introduction: Recent changes in undergraduate medical curricula have resulted in time constraints that are particularly challenging, especially when students must learn large blocks of musculoskeletal anatomy content. Consequently, students have resorted to rote memorization to cope, which counteracts our established collaborative self-directed learning model. Methods: For a 6-week musculoskeletal anatomy course, two structured case-based review sessions are described, each following the completion of two five-hour lab sessions, two on the upper extremities and two on the lower extremities. These largely self-directed review sessions consisted of 6 students rotating through 7 to 8 stations every 10 minutes where clinical cases with follow-up questions were projected on large screens. The students were expected to work collaboratively to solve the cases utilizing the prosected specimens provided and discuss the accompanying answers at the end of each case. Results: Ninety-four per cent of the students who participated in this study agreed that the case-based review sessions provided a helpful overview of musculoskeletal anatomy content. Student performance on the open-ended, case-based musculoskeletal examination questions showed no significant difference in performance on shoulder, hand, hip, thigh, and leg questions. There was, however, a statistically significant decrease in the students' scores on a forearm question in 2021 compared to 2019. Conclusion: This paper describes our integrated, collaborative musculoskeletal course, including case-based review sessions, which was positively received by students as having value in reviewing the musculoskeletal content though it was not found to improve examination performance.

Organ- and function-specific anatomical organization of vagal fibers supports fascicular vagus nerve stimulation.

Vagal fibers travel inside fascicles and form branches to innervate organs and regulate organ functions. Existing vagus nerve stimulation (VNS) therapies activate vagal fibers non-selectively, often resulting in reduced efficacy and side effects from non-targeted organs. The transverse and longitudinal arrangement of fibers inside the vagal trunk with respect to the functions they mediate and organs they innervate is unknown, however it is crucial for selective VNS. Using micro-computed tomography imaging, we tracked fascicular trajectories and found that, in swine, sensory and motor fascicles are spatially separated cephalad, close to the nodose ganglion, and merge caudad, towards the lower cervical and upper thoracic region; larynx-, heart- and lung-specific fascicles are separated caudad and progressively merge cephalad. Using quantified immunohistochemistry at single fiber level, we identified and characterized all vagal fibers and found that fibers of different morphological types are differentially distributed in fascicles: myelinated afferents and efferents occupy separate fascicles, myelinated and unmyelinated efferents also occupy separate fascicles, and small unmyelinated afferents are widely distributed within most fascicles. We developed a multi-contact cuff electrode to accommodate the fascicular structure of the vagal trunk and used it to deliver fascicle-selective cervical VNS in anesthetized and awake swine. Compound action potentials from distinct fiber types, and physiological responses from different organs, including laryngeal muscle, cough, breathing, and heart rate responses are elicited in a radially asymmetric manner, with consistent angular separations that agree with the documented fascicular organization. These results indicate that fibers in the trunk of the vagus nerve are anatomically organized according to functions they mediate and organs they innervate and can be asymmetrically activated by fascicular cervical VNS.

Strategies for precision vagus neuromodulation.

The vagus nerve is involved in the autonomic regulation of physiological homeostasis, through vast innervation of cervical, thoracic and abdominal visceral organs. Stimulation of the vagus with bioelectronic devices represents a therapeutic opportunity for several disorders implicating the autonomic nervous system and affecting different organs. During clinical translation, vagus stimulation therapies may benefit from a precision medicine approach, in which stimulation accommodates individual variability due to nerve anatomy, nerve-electrode interface or disease state and aims at eliciting therapeutic effects in targeted organs, while minimally affecting non-targeted organs. In this review, we discuss the anatomical and physiological basis for precision neuromodulation of the vagus at the level of nerve fibers, fascicles, branches and innervated organs. We then discuss different strategies for precision vagus neuromodulation, including fascicle- or fiber-selective cervical vagus nerve stimulation, stimulation of vagal branches near the end-organs, and ultrasound stimulation of vagus terminals at the end-organs themselves. Finally, we summarize targets for vagus neuromodulation in neurological, cardiovascular and gastrointestinal disorders and suggest potential precision neuromodulation strategies that could form the basis for effective and safe therapies.

A Game-Based Approach to Teaching and Learning Anatomy of the Liver and Portal Venous System.

Introduction: The use of games and game elements as teaching tools has received increasing attention in the medical education literature. Used formatively, games promote student engagement and satisfaction, and encourage collaboration and teamwork among students. They may also help students retain knowledge, although research supporting this notion is limited. This resource contains a 30-minute interactive lab station involving two different game-based activities aimed at teaching functional anatomy of the liver and portal venous system. Methods: The first activity is a flipped version of a traditional pinned anatomy practical, wherein students place their own pins on a body donor in response to application-level prompts. The second activity is an outlay-type card game where students assemble cards to depict the venous drainage of gut organs in a healthy patient versus one with portal hypertension. Results: In end-of-session reviews, several students volunteered feedback that the activities were effective and enjoyable. Additionally, average student scores on two subject exam questions increased by approximately 13% and 4%, compared with students who took the exam before the game elements were introduced. Discussion: These game-based activities may serve as a starting point for others wishing to deal with historically difficult topics in a more engaging way. The tools presented are low-cost, low-tech, and easy to modify for use with different student populations.