Abstract: The septum pellucidum is a thin, translucent double-membrane structure located between the anterior horns of the lateral ventricles. This mini-review explores the gross and radiological anatomy, variations, and clinical significance of the septum pellucidum. The article elaborates on the different types of variations, including cavum septum pellucidum (CSP), cavum vergae (CV), and cavum veli interpositi (CVI). The CSP is a fluid-filled pocket located within the two leaflets of the SP. It forms during fetal development and gradually obliterates before birth. However, the fusion may be prolonged or persist into adulthood in some individuals. The CV is formed when the two commissural plates fail to fuse completely during foetal development. When associated with CSP, the CV is collectively known as the cavum septum pellucidum et vergae (CSPV). However, the isolated CV is rare. The CVI is a CSF-filled space between two tela choroidea layers and communicates with the quadrigeminal cistern, superior to the pineal gland. This article discusses the radiological features of these variations using imaging techniques such as ultrasound, magnetic resonance imaging (MRI), and computed tomography (CT). Ultrasonography is particularly useful for evaluating the SP in fetuses and infants, while MRI and CT scans provide detailed visualisation of the SP and its variations. The SP has the potential to be associated with cerebral anomalies, hydrocephalus, mental disorders, and neurological symptoms. Knowing the related anatomy and detecting variations using imaging modalities are crucial for accurately diagnosing and managing these conditions.

The medial septum (MS), as part of the basal forebrain, supports many physiological functions, from sensorimotor integration to cognition. With often reciprocal connections with a broad set of peers at all major divisions of the brain, the MS orchestrates oscillatory neuronal activities throughout the brain. These oscillations are critical in generating sensory and emotional salience, locomotion, maintaining mood, supporting innate anxiety, and governing learning and memory. Accumulating evidence points out that the physiological oscillations under septal influence are frequently disrupted or altered in pathological conditions. Therefore, the MS may be a potential target for treating neurological and psychiatric disorders with abnormal oscillations (oscillopathies) to restore healthy patterns or erase undesired ones. Recent studies have revealed that the patterned stimulation of the MS alleviates symptoms of epilepsy. We discuss here that stimulus timing is a critical determinant of treatment efficacy on multiple time scales. On-demand stimulation may dramatically reduce side effects by not interfering with normal physiological functions. A precise pattern-matched stimulation through adaptive timing governed by the ongoing oscillations is essential to effectively terminate pathological oscillations. The time-targeted strategy for the MS stimulation may provide an effective way of treating multiple disorders including Alzheimer’s disease, anxiety/fear, schizophrenia, and depression, as well as pain.

Seizure development relies on two factors. One is the existence of an overexcitable neuronal network and the other is a trigger that switches normal activity of that network into a paroxysmal state. While mechanisms of local overexcitation have been the focus of many studies, the process of triggering remains poorly understood. We suggest that, apart from the known exteroceptive sources of reflex epilepsy – visual, auditory or olfactory, there is a range of interoceptive triggers, relevant for seizure development in Temporal Lobe Epilepsy (TLE). The hypothesis proposed here aims to explain the prevalence of epileptic activity in sleep and in drowsiness states and provide a detailed mechanism of seizure triggering by interoceptive signals.

Hippocampus plays a crucial role in spatial and episodic memory. The acquisition of new memories is impossible without participation of the hippocampus. There are two main functional states or “modes” of the hippocampal activity, theta and non-theta state. They have different behavioral correlates and clearly different spectral content of the LFPs and neuronal spiking. Hippocampal theta state is present under active exploratory behavior, locomotion, cognitive situations requiring attention and REM sleep. Slow-wave sleep and quiet wakefulness (immobility, eating, grooming) represent the non-theta hippocampal state. The nodal point for the regulation of hippocampal activity is the MS. The activation or suppression of different types of MS cells appears to be responsible for controlling hippocampal theta and non-theta states. Functional coupling between MS neurons and hippocampal interneurons varies in a state-dependent manner.

Heart myocardia are critical to the facilitation of heart pumping and blood circulating around the body. The biaxial mechanical testing of the Left Ventricle (RV) is utilised to build the computa-tional model of the whole heart with little importance given to the unique mechanical properties of Right Ventricle (RV) and Mid-wall (MDW). Most of those studies focussed on the LV of the heart, and then apply the obtained characteristics with a few modifications to the right side of the heart. However, that view has been contested over time with the realisation that the right side of the heart possesses its own unique mechanical properties that are widely distinct from that of the left side of the heart. This paper is aimed at reporting and evaluating the passive mechanical property dif-ferences in the three main walls of the rat heart based on biaxial tensile test data. Fifteen mature Wistar rats weighing 225 ± 25 g were euthanised by inhalation of 5 % halothane. The hearts were excised after which all the top chambers comprising the two atria, pulmonary and vena cava trunks, aorta and valves are all dissected out. Then 5 x 5 mm sections from the middle of each wall were carefully dissected with a surgical knife to avoid over-prestraining the specimens. The specimens were subjected tensile test. The elastic moduli, peak stresses in the toe region and stresses at 40 % strain, anisotropy indices as well as the stored strain energy in the toe and linear region up to 40 % strain are used for statistical significance tests. The following are the main findings of this study: (1) LV and MDW tissues have relatively shorter toe regions of 10 - 15 % strain as compared to RV tissue whose toe region extends up to twice as much as that (2) LV tissues have higher strain energy storage in the linear region despite being lower in stiffness than the RV (3) the MDW has the highest strain energy storage along both directions which might be directly related to its high level of anisotropy. These findings, though for a specific animal species at similar age and around the same body mass, emphasize the importance of application of wall specific material parameters to obtain accurate ventricular hyperelastic models. The findings further enhance our understanding of the desired mechanical behaviour of the different ventricle walls.

The beating heart is subject to intrinsic mechanical factors, exerted by contraction of the myocardium (stretch and strain) and fluid forces of the enclosed blood (wall shear stress). The earliest contractions of the heart occur already in the 10-somite stage in the tubular as yet unsegmented heart. With development the looping heart becomes asymmetric providing varying diameters and curvatures resulting in unequal flow profiles. These flow profiles exert various wall shear stresses and as a consequence different expression patterns of shear responsive genes. In this paper we investigate the morphological changes of the heart after changes the blood flow by ligation of the right vitelline vein in a model chicken embryo and analyze the extended expression in the endocardial cushions of the shear responsive gene Tgfbeta receptor III. A major phenomenon is the diminished endocardial-mesenchymal transition resulting in hypoplastic (even absence of) atrioventricular and outflow tract endocardial cushions, that might be lethal in early phases. The surviving embryos exhibit several cardiac malformations including ventricular septal defects and malformed semilunar valves related to a malposition of the aortopulmonary septum and the enclosed neural crest cells. We discuss the results in the light of the interactions between several shear stress responsive signaling pathways including Vegf, Notch, Pdgf, Klf2, eNos, Endothelin and Tgfβ/Bmp/Smad.