Abstract

The medial part of the olfactory tubercle (OT) is a brain structure located at the interface of the reward and olfactory system. It is closely related to pheromone-rewards, natural reinforcement, addiction and many other behaviors. However, the structure of the anatomic circuitry of the medial part of the OT is still unclear. In the present study, the medial part of the OT was found to be highly connected with a wide range of brain areas with the help of the pseudorabies virus tracing tool. In order to further investigate the detailed connections for specific neurons, another tracing tool – rabies virus was utilized for D1R-cre and D2R-cre mice. The D1R and D2R neurons in the medial part of the OT were both preferentially innervated by the olfactory areas, especially the piriform cortex, and both had similar direct input patterns. With the help of the adeno-associated virus labeling, it was found that the two subpopulations of neurons primarily innervate with the reward related brain regions, with slightly less axons projecting to the olfactory areas. Thus, the whole-brain input and output circuitry structures for specific types of neurons in the medial part of the OT were systematically investigated, and the results revealed many unique connecting features. This work could provide new insights for further study into the physiological functions of the medial part of the OT.

Highlights

  • The olfactory tubercle (OT), as its name indicates, is a key part of the olfactory sensory cortex that receives direct inputs from the olfactory bulb (OB) (Pigache, 1970; Xiong and Wesson, 2016)

  • Since the pseudorabies virus (PRV) labeling strategy for input circuitries is timedependent (Figure 1A), the labeled patterns of the wholebrain were examined at two different time points post-infection (Figures 1B, 2)

  • With a longer infection time (64 h post PRV-152 injection), a much wider range of brain regions were observed with GFP-positive labels, including the entire OB, AMY and lateral septal complex (LSX), most parts of the cerebral cortex, interbrain, midbrain and hindbrain

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Summary

Introduction

The olfactory tubercle (OT), as its name indicates, is a key part of the olfactory sensory cortex that receives direct inputs from the olfactory bulb (OB) (Pigache, 1970; Xiong and Wesson, 2016). The OT is the only sensory cortex located in the striatum, and it has many direct or indirect connections with the olfactory system (Xiong and Wesson, 2016) It possesses the “Islands of Calleja” (IC), which is unique among rodents’ brains (Adjei and Wesson, 2015); and dynamic laminations containing “hills” and “valleys,” which are not found in any other cortex structures. These anatomical features endowed the OT with

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