Nucleus accumbens

The nucleus accumbens (NAcc), also known as the accumbens nucleus or as the nucleus accumbens septi (Latin for nucleus adjacent to the septum) is a region in the basal forebrain rostral to the preoptic area of the hypothalamus.

The nucleus accumbens and the olfactory tubercle collectively form the ventral striatum, which is part of the basal ganglia.

Each cerebral hemisphere has its own nucleus accumbens. It is located where the head of the caudate nucleus and the anterior portion of the putamen meet just lateral to the septum pellucidum.

Function

The nucleus accumbens can be divided into two structures—the nucleus accumbens core and the nucleus accumbens shell. These structures have different morphology and function.

Cocaine use followed by withdrawal induces synaptic plasticity in the nucleus accumbens (NAc), which are thought to underlie subsequent drug-seeking behaviors and relapse. Previous studies suggest that cocaine-induced synaptic changes depend on acid-sensing ion channels (ASICs). Gupta et al. investigated the potential involvement of carbonic anhydrase 4 (CA4), an extracellular pH-buffering enzyme. They examined the effects of CA4 in mice on ASIC-mediated synaptic transmission in medium spiny neurons (MSNs) in NAc, as well as on cocaine-induced synaptic changes and behavior. They found that CA4 is expressed in the NAc and present in synaptosomes. Disrupting CA4 either globally, or locally, increased ASIC-mediated synaptic currents in NAc MSNs and protected against cocaine withdrawal-induced changes in synapses and cocaine-seeking behavior. These findings raise the possibility that CA4 might be a previously unidentified therapeutic target for addiction and relapse ¹⁾.

Research has indicated the nucleus accumbens has an important role in pleasure including laughter, reward, and reinforcement learning, as well as fear, aggression, impulsivity, addiction, and the placebo effect.

Previous imaging studies independently highlighted the role of the anterior thalamus (ANT) and nucleus accumbens (NAcc) in successful memory retrieval. While these findings accord with theoretical models, the precise temporal, oscillatory and network dynamics as well as the interplay between the NAcc and ANT in successfully retrieving information from long-term memory are largely unknown.

The University of Hamburg, Lübeck and Magdeburg in Germany addressed this issue by recording intracranial electroencephalography in human epilepsy patients from the NAcc (n = 5) and ANT (n = 4) during an old/new recognition test.

The findings demonstrate that differences in event-related potentials between correctly classified old (i.e., studied) and new (i.e., unstudied) images emerged in the NAcc and ANT already between 200 and 600 ms after stimulus onset. Moreover, time-frequency analyses revealed theta (4-8 Hz) power decreases for old compared to new items in the NAcc and the opposite effect in the ANT. Importantly, Granger causality analyses revealed a directional communication from ANT to NAcc suggesting that entrainment from ANT drives successful memory retrieval.

Together, this findings show evidence for the notion that the NAcc and ANT receive memory signals, and that theta oscillations may serve as a mechanism to bind these distributed neural assemblies ²⁾.

Deep brain stimulation of the nucleus accumbens

see Deep brain stimulation of the nucleus accumbens.