THREE-DIMENSIONAL RECONSTRUCTION OF THE ANTERIOR OLFACTORY NUCLEUS IN THE HUMAN OLFACTORY BULB AND PEDUNCLE. Reconstrucción tridimiensional del núcleo olfatorio anterior en el bulbo y pedúnculo olfatorio humano

Abstract

El bulbo y pedúnculo olfatorio humano contienen muchos grupos celulares más o menos separados que habitualmente son considerados como parte del núcleo olfatorio anterior retro-bulbar (AON). La presunción que estos grupos celulares sean considerados como extensión rostral del AON en el hemisferio rostral retrocede a la descripción de un único caso por Crosby y Humphrey (1941). Para mejorar nuestra comprensión de la anatomía del AON bulbar y peduncular humano investigamos la morfología, forma y tamaño de estas partes en este núcleo en tejido post-mortem de individuos de edades conocidas. Se obtuvieron seis bulbos y pedúnculos olfatorios, incluyendo la sustancia perforada anterior (SPA), de cerebros donados; se realizaron cortes seriales horizontales a 40µm y se tiñó con substancia de Nissl. Las neuronas de tamaño mediano a grande de esta parte del AON se tiñeron intensamente y tenían un diámetro promedio de 16µm. La reconstruc-ción tridimensional demostró que en todos los casos, excepto uno, el AON bulbar y peduncular consistieron en una cadena discontinua de grupos celulares conectados por puentes de neuropilas pobres o libres de células. El número de grupos celulares y de puentes conectores difiere en cada individuo. Concluimos que las porciones bulbar y peduncular del AON humano debería ser considerado como una especialización humana más que como una extensión rostral del área AON retro-bulbar. Esto es acorde con las propiedades neuro-clínicas previamente publicadas y la degeneración temprana selectiva, pre-clínica, de estos nichos celulares en la enfermedad neuro-degenerativa. The human olfactory bulb and peduncle contain several more or less separated cell groups that are usually regarded to be part of the retrobulbar anterior olfactory nucleus (AON). The assumption that these cell groups are to be considered as the rostral extension of the AON in the rostral hemisphere goes back to the description of one single case by Crosby and Humphrey (1941). To improve our understanding of the anatomy of the human bulbar and peduncular AON, we investigated the morphology, size and shape of these parts of this nucleus in postmortem tissue of aged individuals. Six olfactory bulbs and peduncles including the substantia perforata anterior (SPA) were obtained from donor brains and 40µm horizontal serial sections were cut and stained with Nissl substance. The medium to large sized neurons of these parts of the AON were intensely stained and had an average diameter of 16µm. Three dimensional reconstruction demonstrated that in all but one of the cases the bulbar and peduncular AON consisted on a discontinuous chain of cell groups connected by cell poor to cell free bridges of neuropile. The number of cell groups and the connecting bridges differ in every individual. We arrived at the conclusion that the bulbar and peduncular parts of the human AON should be regarded a human specialization rather than just being rostral extensions of the retrobulbar AON area. This is in line with previously published neurochemical properties and the selective early, preclinical degener-ation of these cell clusters in neurodegenerative diseases.

α-synuclein inclusions are abundant in non-neuronal cells in the anterior olfactory nucleus of the Parkinson’s disease olfactory bulb

“…The size and location of the AON can vary between sections within the same OFB and therefore significantly between different OFB cases. It also remains unclear whether the different AON segments are connected or have functionally distinctive roles 36 . In this study, we used four cellular markers to target different structures of the OFB to more accurately delineate the AON, however, we did not make a distinction between the AON subdivisions (Fig.…”

The olfactory striae: A historical perspective on the inconsistent anatomy of the bulbar projections

“…The superior stria corresponds to what Crosby and Humphrey (1941) called the pars dorsalis of the AON. In humans, such a subdivision is not obvious, and other subdivisions of the AON have been proposed (Berendsen et al, 2015; Kundu et al, 2013; Lane et al, 2020; Ubeda‐Banon et al, 2010).…”