The hippocampus is essential for the formation and retrieval of memories and is a crucial neural structure sub-serving complex cognition. Adult hippocampal neurogenesis, the birth, migration and integration of new neurons, is thought to contribute to hippocampal circuit plasticity to augment function. We evaluated hippocampal volume in relation to brain volume in 375 mammal species and examined 71 mammal species for the presence of adult hippocampal neurogenesis using immunohistochemistry for doublecortin, an endogenous marker of immature neurons that can be used as a proxy marker for the presence of adult neurogenesis. We identified that the hippocampus in cetaceans (whales, dolphins and porpoises) is both absolutely and relatively small for their overall brain size, and found that the mammalian hippocampus scaled as an exponential function in relation to brain volume. In contrast, the amygdala was found to scale as a linear function of brain volume, but again, the relative size of the amygdala in cetaceans was small. The cetacean hippocampus lacks staining for doublecortin in the dentate gyrus and thus shows no clear signs of adult hippocampal neurogenesis. This lack of evidence of adult hippocampal neurogenesis, along with the small hippocampus, questions current assumptions regarding cognitive abilities associated with hippocampal function in the cetaceans. These anatomical features of the cetacean hippocampus may be related to the lack of postnatal sleep, causing a postnatal cessation of hippocampal neurogenesis.

Sleep plays an important role in maintaining neuronal circuitry, signalling and helps maintain overall health and wellbeing. Sleep deprivation (SD) disturbs the circadian physiology and exerts a negative impact on brain and behavioural functions. SD impairs the cellular clearance of misfolded neurotoxin proteins like α-synuclein, amyloid-β, and tau which are involved in major neurodegenerative diseases like Alzheimer’s disease and Parkinson’s disease. In addition, SD is also shown to affect the glymphatic system, a glial-dependent metabolic waste clearance pathway, causing accumulation of misfolded faulty proteins in synaptic compartments resulting in cognitive decline. Also, SD affects the immunological and redox system resulting in neuroinflammation and oxidative stress. Hence, it is important to understand the molecular and biochemical alterations that are the causative factors leading to these pathophysiological effects on the neuronal system. This review is an attempt in this direction. It provides up-to-date information on the alterations in the key processes, pathways, and proteins that are negatively affected by SD and become reasons for neurological disorders over a prolonged period of time, if left unattended.

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Anatomy departments across Africa were surveyed regarding the type of curriculum and method of delivery of their medical courses. While the response rate was low, African anatomy departments appear to be in line with the rest of the world in that many have introduced problem based learning, have hours that are within the range of western medical schools and appear to be well resourced. Human body dissection is a constant and strong aspect of the majority of the courses surveyed. The staff to student ratio appears to be relatively high in Africa, but in many of the responding African institutions, there appears to be little difficulty in attracting suitable faculty (including those who are medically qualified) to teach anatomy. Retaining this faculty, in some cases, may be difficult because of a global demand for anatomy educators.

Here, we describe the superficial appearance of the brain of the rarely studied tree pangolin. Phylogenetic analyses have placed the pangolins, order Pholidota, as a sister group to the order Carnivora. The majority of features visible on the surface of the tree pangolin brain, and its overall appearance can be described as typically mammalian. The pattern of sulci and gyri, while simple, appears very similar to that observed in carnivores. Two derived features of the Pholidota were observed, the first being the rostral decussation of the pyramidal tract, which instead of occurring at the spinomedullary junction, decussates at the level of the caudal pole of the facial nerve nucleus in the rostral medulla oblongata. This appears to be related to the need for voluntary control of the tongue, with a potentially enlarged corticobulbar tract ending in the hypoglossal nucleus. The second derived feature is the very short spinal cord, which terminates midway along the thoracic vertebrae before giving rise to a long and extensive cauda equina. This foreshortened spinal cord appears to be related to anisotropic growth of the somatic and neural elements following early development of the central nervous system. The olfactory system appears to be generally enlarged and is likely the predominant sense used in foraging. Vision and hearing do not appear specialized based on the relative size of the superior and inferior colliculi, but potential somatic specializations indicate that the somatosensory system is heavily relied upon for food consumption and prehensile tail usage.

This study employed a range of neuroanatomical stains to determine the organization of the main and accessory olfactory systems within the brain of the tree pangolin. The tree pangolin has a typically mammalian olfactory system, but minor variations were observed. The main olfactory system is comprised of the layered main olfactory bulb (MOB), the anterior olfactory nucleus (AON), the rostral olfactory cortex (including the taenia tecta, anterior hippocampal continuation and induseum griseum), the olfactory tubercle (Tu), the lateral olfactory tract (lot) and the olfactory limb of the anterior commissure, the nucleus of the lateral olfactory tract (NLOT), the piriform cortex (PIR) and a typically mammalian rostral migratory stream (RMS). The accessory olfactory system included the layered accessory olfactory bulb (AOB) and the nucleus of the accessory olfactory tract (NAOT). Volumetric analysis of the relative size of the MOB and PIR indicate that the tree pangolin has an olfactory system that occupies a proportion of the brain typical for the majority of mammals. Within the MOB, the glomeruli of the tree pangolin, at 200 μm diameter, are larger than observed in most other mammalian species, and the MOB lacks a distinct internal plexiform layer. In addition, the laminate appearance of the NLOT was not observed in the tree pangolin. The accessory olfactory system appears to lack the posterior compartment of the accessory olfactory bulb. These observations are contextualized in relation to olfactory-mediated behaviors in pangolins.

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