Anterior olfactory nucleus
Encyclopedia
The anterior olfactory nucleus (AON; also called the anterior olfactory cortex) is a portion of the forebrain of vertebrate
s.
It is involved in olfaction
.
and in front of the piriform cortex
(laterally) and olfactory tubercle
(medially) in a region often referred to as the olfactory peduncle or retrobulbar area. The peduncle contains the AON as well as two other much smaller regions, the tenia tecta (or dorsal hippocampal rudiment) and the dorsal peduncular cortex.
Odors enter the nose (or olfactory rosette in fishes) and interact with the cilia of olfactory receptor neurons. The information is sent via the olfactory nerve (Cranial Nerve I) to the olfactory bulb. After the processing in the bulb the signal is transmitted caudally via the axons of mitral and tufted cells in the lateral olfactory tract. The tract forms on the ventrolateral surface of the brain and passes through the AON, continuing on to run the length of the piriform cortex, while synapsing in both regions. The AON distributes the information to the contralateral olfactory bulb and piriform cortex as well as engaging in reciprocal interactions with the ipsilateral bulb and cortex. Therefore, the AON is positioned to regulate information flow between nearly every region where odor information processing occurs.
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s.
It is involved in olfaction
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
.
Location
The AON is found behind the olfactory bulbOlfactory bulb
The olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors.-Anatomy:In most vertebrates, the olfactory bulb is the most rostral part of the brain. In humans, however, the olfactory bulb is on the inferior side of the brain...
and in front of the piriform cortex
Piriform cortex
In anatomy of animals, the piriform cortex, or pyriform cortex is a region in the brain.-Anatomy and function:The piriform cortex is part of the rhinencephalon situated in the telencephalon....
(laterally) and olfactory tubercle
Olfactory tubercle
The olfactory tubercle is a structure involved in Olfaction.It is present in humans, but much smaller than it is in some other animals.It is a frequent subject of research.-External links:...
(medially) in a region often referred to as the olfactory peduncle or retrobulbar area. The peduncle contains the AON as well as two other much smaller regions, the tenia tecta (or dorsal hippocampal rudiment) and the dorsal peduncular cortex.
Function
The AON plays a pivotal but relatively poorly understood role in the processing of odor information.Odors enter the nose (or olfactory rosette in fishes) and interact with the cilia of olfactory receptor neurons. The information is sent via the olfactory nerve (Cranial Nerve I) to the olfactory bulb. After the processing in the bulb the signal is transmitted caudally via the axons of mitral and tufted cells in the lateral olfactory tract. The tract forms on the ventrolateral surface of the brain and passes through the AON, continuing on to run the length of the piriform cortex, while synapsing in both regions. The AON distributes the information to the contralateral olfactory bulb and piriform cortex as well as engaging in reciprocal interactions with the ipsilateral bulb and cortex. Therefore, the AON is positioned to regulate information flow between nearly every region where odor information processing occurs.
Components
The AON is composed of two separate structures:- a) a thin ring of cells encircling the rostral end of the olfactory peduncle known as “pars externa”,
- b) the large “pars principalis”, seen in coronal sections of most mammalian brains as a two-layered structure.
- The deepest (Layer II) is a thick ring of pyramidal and other-shaped cells surrounding the anterior limb of the anterior commissure.
- The outer, cell-poor layer, is often subdivided into a superficial zone (Layer Ia, which contains the output axons from the olfactory bulb) and a deeper area (Layer Ib).
- Many divide pars principalis on the basis of the ‘compass points,’ yielding pars dorsalis, pars ventralis, pars medialis, pars lateralis, and pars posterioralis (often combined with pars ventralis to form “pars ventroposterioralis”).
External links
- NIF Search - Anterior Olfactory Nucleus via the Neuroscience Information FrameworkNeuroscience Information FrameworkThe Neuroscience Information Framework is a repository of global neuroscience web resources, including experimental, clinical, and translational neuroscience databases, knowledge bases, atlases, and genetic/genomic resources.-Description:...