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Accumbens

Published: Jul 10, 2023
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Updated: Jul 30, 2023
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Written by Oseh Mathias

Founder, SpeechFit

The nucleus accumbens, often referred to as the accumbens, is a region in the brain that plays a critical role in the reward, pleasure, and reinforcement learning system [1]. It's involved in both aversive and appetitive behaviors [2], and its connection to the hippocampus and prefrontal cortex implicates it in memory and cognitive function, particularly in aspects related to reward-related cognitive processes [3][4].

The nucleus accumbens is located in the basal forebrain in the ventral part of the striatum, which is a part of the basal ganglia [5]. It is anterior to the preoptic area of the hypothalamus and resides near the intersection of the putamen and the head of the caudate nucleus [6].

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The accumbens shown as a red dot at the base of brain near the hypothalamus. Davidoff, A. (n.d.)[7]

The accumbens is divided into two primary anatomical subdivisions: the core and the shell.

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Schematic (left) and photomicrographic representation (right) of the locations of injector tips in the NAc core and shell, based on the stereotaxic atlas of the rat brain of Paxinos and Watson (1997). [8]

The nucleus accumbens plays a crucial role in several important brain pathways, particularly the mesolimbic and mesocortical pathways.

In the mesolimbic pathway, often referred to as the brain's reward pathway, dopamine neurons in the ventral tegmental area (VTA) send projections to the nucleus accumbens [9]. When an event or stimulus is perceived as rewarding, these neurons release dopamine into the nucleus accumbens, contributing to the experience of pleasure and the motivation to seek out rewarding stimuli [10]. This pathway is also crucial for learning to associate certain stimuli or behaviours with reward [11].

In the mesocortical pathway, which also originates in the VTA but primarily projects to the prefrontal cortex, the nucleus accumbens plays an indirect but significant role [12]. The nucleus accumbens helps to determine the value of a reward, while the prefrontal cortex may use this information to guide decision-making and action selection [13].

The nucleus accumbens is not only found in humans; rather it or a structure like it is found in many vertebrates.

In mammals, such as rodents and non-human primates, the nucleus accumbens plays a similar role to that in humans, with involvement in reward anticipation, motivation, and reinforcement learning [14]. Birds have an avian equivalent of the nucleus accumbens, playing a role in song learning, which is a form of reward-dependent learning [15]. A structure equivalent to the nucleus accumbens has also been identified in fish, such as zebrafish, suggesting similar functions related to reward and reinforcement [16]. In reptiles, the nucleus accumbens or a homologous structure is involved in decision-making behaviours [17].

Author

Oseh Mathias

SpeechFit Founder

Oseh is passionate about improving health and wellbeing outcomes for neurodiverse people and healthcare providers alike.

References

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  • Ikemoto, S. (2007). Dopamine reward circuitry: two projection systems from the ventral midbrain to the nucleus accumbens–olfactory tubercle complex. Brain Research Reviews, 56(1), 27–78. https://doi.org/10.1016/j.brainresrev.2007.05.004

  • Heimer, L., Zahm, D. S., Churchill, L., Kalivas, P. W., & Wohltmann, C. (1991). Specificity in the projection patterns of accumbal core and shell in the rat. Neuroscience, 41(1), 89–125. https://doi.org/10.1016/0306-4522(91)90202-Y

  • Davidoff, A. (n.d.). Nucleus Accumbens of the Brain. Sensation of Pleasure. [Digital image]. Art in Anatomy. Retrieved July 19, 2023, from https://www.artinanatomy.com/shop/brain/nucleus-accumbens-of-the-brain-sensation-of-pleasure/

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  • Heinig, A., Pant, S., Dunning, J., Bassett, D. S., Schroeder, I. S., & Roberts, T. F. (2018). A mechanism for rapid song-related motor encoding in vocal premotor cortex. bioRxiv.

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