[3] The OT is a composite structure that receives direct input from the olfactory bulb and contains the morphological and histochemical characteristics of the ventral pallidum and the striatum of the forebrain.

The olfactory tubercle differs in location and relative size between humans, other primates, rodents, birds, and other animals.

[7] In humans and other primates, visual identification of the olfactory tubercle is not easy because the basal forebrain bulge is small in these animals.

These cell clusters, called the islands of Calleja, are innervated by dopaminergic projections from the nucleus accumbens and the substantia nigra, suggesting the role that the olfactory tubercle plays in the reward system.

Due to its many innervations from other brain regions, the olfactory tubercle is involved in merging information across the senses, such as olfactory/audition and olfactory/visual integrations, possibly in a behaviorally relevant manner.

Unilateral lesions in the olfactory tubercle have been shown to alter attention, social and sensory responsiveness, and even locomotor behavior.

Rats have been shown to administer cocaine into the olfactory tubercle more than the nucleus accumbens and ventral pallidum, other reward centers in the brain.

Thus, it may link perception of odor with action through its connections with attention, reward, and motivation systems of the basal forebrain.

[3] Functional imaging data from this same group also shows that the olfactory tubercle is highly activated during tasks that engage attention, thus playing a large role in arousal-related systems.

Because the olfactory tubercle is a component of the ventral striatum, it is heavily interconnected with several affective-, reward-, and motivation-related centers of the brain.

[8] Other than the islands of Calleja, which are characteristic of the tubercle,[15] it is also noted for the being innervated by dopaminergic neurons from the ventral tegmental area.

The olfactory tubercle also consists of heterogeneous elements, such as medial forebrain bundle, and has a ventral extension of the striatal complex.

[20] Olfactory tubercle neurons originate as early as embryonic day 13 (E13), and the cell development occurs in a layer specific manner.

[2] These stereotyped inhibitions may have been caused by the removal of central neuronal processes other than the dopaminergic cells in the olfactory tubercle.

Many studies have found reduced olfactory sensitivity in patients with major depressive disorders (MDD) and dementia and schizophrenia.

Rupp, et al.[9] found that in patients with schizophrenia olfactory sensitivity and discrimination as well as higher order identification abilities are reduced.

As mentioned earlier, the olfactory tubercle may be involved in the perception of odors due to the inputs received from the bulb and thus, by extension, may play a role in these psychiatric disorders.

Since then, there have been several histological and histochemical studies;[2][8] done in this area to identify it in other rodents, cats, humans, non-human primates, and other species.

[35][36] Improvements in technology have made it possible to now place multiple electrodes in the olfactory tubercle and record from anesthetized and even awake animals participating in behavioral tasks.