Ammon's horn and the hippocampus

Gods and monsters: Greek mythology and Christian references in the neurosurgical lexicon

Background:

Myths and religion are belief systems centered around supernatural entities that attempt to explain the observed world and are of high importance to certain communities. The former is a collection of stories that belong to a cultural tradition and the latter are organized faiths that determine codes of ethics, rituals and philosophy. Deities or monstrous creatures in particular act as archetypes instructing an individual’s conduct. References to them in Greek mythology and Christianity are frequently manifested in the modern neurosurgical vernacular.

Methods:

A review of the medical literature was performed using the PubMed and MEDLINE bibliographic databases. Publications from 1875 to 2021 related to neurosurgery or neuroanatomy with the medical subject headings (MeSH) terms mythology, religion, Christianity and Catholicism were reviewed. References pertaining to supernatural beings were classified to either a deity or a monstrosity according to their conventional cultural context.

Results:

Twelve narratives associated with neurosurgery were identified, nine relating to Greek mythology and three associated with the Christian-Catholic faith. Eight accounts concerned deities and the remaining with monstrous creatures.

Conclusion:

This article explores the etymology of commonly utilized terms in daily neurosurgical practice in the context of mythology and religion. They reveal the ingenuity and creativity of early pioneers who strived to understand the brain.

Morris water maze: a versatile and pertinent tool for assessing spatial learning and memory

Since its development about 40 years ago (1981–2021), Morris water maze has turned into a very popular tool for assessing spatial learning and memory. Its many advantages have ensured its pertinence to date. These include its effectiveness in evaluating hippocampal-dependent learning and memory, exemption from motivational differences across diverse experimental manipulations, reliability in various cross-species studies, and adaptability to many experimental conditions with various test protocols. Nonetheless, throughout its establishment, several experimental and analysis loopholes have galvanized researchers to assess ways in which it could be improved and adapted to fill this gap. Therefore, in this review, we briefly summarize these developments since the early years of its establishment through to the most recent advancements in computerized analysis, offering more comprehensive analysis paradigms. In addition, we discuss the adaptability of the Morris water maze across different test versions and analysis paradigms, providing suggestions with regard to the best paradigms for particular experimental conditions. Hence, the proper selection of the experimental protocols, analysis paradigms, and consideration of the assay’s limitations should be carefully considered. Given that appropriate measures are taken, with various adaptations made, the Morris water maze will likely remain a relevant tool to assess the mechanisms of spatial learning and memory.

Neuroprotective effects of phytosterol esters against high cholesterol-induced cognitive deficits in aged rat

Accumulating epidemiological and experimental studies have confirmed that a high-cholesterol diet is detrimental to cognitive performance in animal models.

Julius Caesar Arantius (Giulio Cesare Aranzi, 1530–1589) and the hippocampus of the human brain: history behind the discovery

Julius Caesar Arantius is one of the pioneer anatomists and surgeons of the 16th century who discovered the different anatomical structures of the human body. One of his prominent discoveries is the hippocampus. At that time, Arantius originated the term hippocampus, from the Greek word for seahorse (hippos [“horse”] and kampos [“sea monster”]). Arantius published his description of the hippocampus in 1587, in the first chapter of his work titled De Humano Foetu Liber. Numerous nomenclatures of this structure, including “white silkworm,” “Ammon's horn,” and “ram's horn” were proposed by different scholars at that time. However, the term hippocampus has become the most widely used in the literature.

A comparative study on the effect of high cholesterol diet on the hippocampal CA1 area of adult and aged rats

Dementia is one of the most important problems nowadays. Aging is associated with learning and memory impairments. Diet rich in cholesterol has been shown to be detrimental to cognitive performance. This work was carried out to compare the effect of high cholesterol diet on the hippocampus of adult and aged male albino rats. Twenty adult and twenty aged male rats were used in this study. According to age, the rats were randomly subdivided into balanced and high cholesterol diet fed groups. The diet was 15 g/rat/day for adult rats and 20 g/rat/day for aged rats for eight weeks. Serial coronal sections of hippocampus and blood samples were taken from each rat. For diet effect evaluation, Clinical, biochemical, histological, immunohistochemical, and morphometric assessments were done. In compare to a balanced diet fed rat, examination of Cornu Ammonis 1 (CA 1) area in the hippocampus of the high cholesterol diet adult rats showed degeneration, a significant decrease of the pyramidal cells, attenuation and/or thickening of small blood vessels, apparent increase of astrocytes and apparent decrease of Nissl's granules content. Moreover, the high cholesterol diet aged rats showed aggravation of senility changes of the hippocampus together with Alzheimer like pathological changes. In conclusion, the high cholesterol diet has a significant detrimental effect on the hippocampus and aging might pronounce this effect. So, we should direct our attention to limit cholesterol intake in our food to maintain a healthy life style for a successful aging.

Novel functions of GABA signaling in adult neurogenesis

Neurotransmitter gamma-aminobutiric acid (GABA) through ionotropic GABA_A and metabotropic GABA_B receptors plays key roles in modulating the development, plasticity and function of neuronal networks. GABA is inhibitory in mature neurons but excitatory in immature neurons, neuroblasts and neural stem/progenitor cells (NSCs/NPCs). The switch from excitatory to inhibitory occurs following the development of glutamatergic synaptic input and results from the dynamic changes in the expression of Na⁺/K⁺/2Cl^- co-transporter NKCC1 driving Cl^- influx and neuron-specific K⁺/Cl^- co-transporter KCC2 driving Cl^- efflux. The developmental transition of KCC2 expression is regulated by Disrupted-in-Schizophrenia 1 (DISC1) and brain-derived neurotrophic factor (BDNF) signaling. The excitatory GABA signaling during early neurogenesis is important to the activity/experience-induced regulation of NSC quiescence, NPC proliferation, neuroblast migration and newborn neuronal maturation/functional integration. The inhibitory GABA signaling allows for the sparse and static functional networking essential for learning/memory development and maintenance.

A note on the sea-horse in the human brain

It is commonly believed that the term hippocampus represents a shining example of inappropriate and fanciful anatomical naming, because this brain structure supposedly does not display any resemblance, striking or remote, to the little sea-horse fish known as hippocampus. The aim of this short historical notice is to demonstrate that, in fact, the hippocampus looks very much like the little sea-horse fish, as demonstrated by Gustav Retzius more than a century ago. However, to note this striking resemblance, one has to apply a proper method of anatomical dissection.