Portion of the forebrain of vertebrates
The anterior olfactory nucleus (AON) also called the anterior olfactory cortex, is a major early processing area for olfaction located behind the olfactory bulb, and in the olfactory tract (olfactory peduncle). The AON connects the olfactory processing centres of both hemispheres. 
It is involved in the sense of smell (olfaction), and has influence on other olfactory areas including the olfactory bulb and the piriform cortex. The AON is one of the major secondary structures of olfaction.
Structure.
The AON is found behind the olfactory bulb and in front of the piriform cortex (laterally) and olfactory tubercle (medially) in the olfactory tract (also olfactory peduncle) or retrobulbar area. The peduncle contains the AON as well as two other much smaller regions, the ventral and dorsal tenia tecta.
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 (CNI) to the olfactory bulb. After processing in the bulb the signal is transmitted caudally via the axons of mitral cells, 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:
References.
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