Nucleus Accumbens

Decades of neuroscientific research have allowed scientists to identify the role of specific regions in the brain. One of these regions is the nucleus accumbens, a key structure regulating our ‘motivational and emotional processes.’ Our sense of motivation and psychological wellbeing colour our daily experiences. Changes to these two key areas can lead to us feeling like we are on rocky water. When these feel out of balance, we may find signs of psychiatric distress begin to creep in. Research has identified that activity in the nucleus accumbens can be linked with a range of mental health conditions, including addiction. But why is this the case? What is the function of the nucleus accumbens, and what are the risks of inappropriate activity in this region of the brain? Can difficulties with this structure be regulated, and what does this mean in addiction treatment?

What is the Nucleus-accumbens?

The nucleus accumbens (sometimes shortened to NAc) is a ‘subcortical brain structure,’ or nerve centre below the cerebral cortex. This area of the brain is linked with four key processes and sensations:

• Pleasure
• Reward
• Addiction 
• Pain 

It has been implicated in a range of conditions, including:

• Addiction
• Alzheimer’s
• Anxiety 
• Depression
• Huntington’s disease
• Obesity 
• Obsessive-compulsive disorder (OCD)
• Parkinson’s

Scientists have suggested that the nucleus accumbens could be targeted for a range of physical and psychological health conditions due to its ‘wide range of neural connections.’ 

Where is It?

In a  2D diagram, the nucleus accumbens shows as a small red dot near the centre of the brain. The nucleus accumbens is part of ventral striatum, a larger area in the brain linked with motivational processes. It is situated in the basal forebrain which is thought to be one of the major outputs of the central nervous system. 

What is its function?

The nucleus accumbens has been linked with the limbic system (areas of the brain associated with our behaviour and emotions). It is thought of as a ‘neural interface between motivation and action,’ meaning that this part of the brain is linked with the way we process and interact with stimuli. In particular, the nucleus accumbens affects our motivation in several key areas, such as:

• Feeding and eating 
• Sexual desire
• Feelings of reward 
• Management of stress
• ‘Drug self-administration behaviours.’

In short, the nucleus accumbens is the site of our drive to do things. Typically, motivation comes from one key chemical in the brain: dopamine. 

Nucleus-accumbens and addiction

What is dopamine?

Dopamine is a neurotransmitter that acts in our brains. It is a naturally occurring chemical messenger that sends messages between brain cells through a process called synaptic transmission. Dopamine is known as the ‘pleasure’ chemical, as studies have shown that higher dopamine activity is typically linked with feelings of happiness. But dopamine is also responsible for building associations. Our brains build a series of neural pathways or connections. When we learn something new, brand-new connections are formed. When dopamine is stimulated – for example, after eating a sweet treat – we can feel a rush of pleasure. However, because dopamine is also associated with reward, the ‘feel good feeling’ of dopamine is not only short-lived. If we soon find ourselves craving dessert after eating sweet things regularly, it may well be that our dopaminergic system has shifted to associate the stimulus of sugar with an output of pleasure and reward. And when we feel good for doing something, we typically feel like doing it again. This builds dopaminergic cycles that reinforce engagement with specific objects, substances and behaviours – and it is often what is thought to be at the centre of addiction psychology. 

What does dopamine do?

In moderation, dopamine is great for our wellbeing. It can help us to sleep, to have a regular appetite, to think clearly, to feel more balanced and generally more comfortable. The issue is not always with dopamine itself, but rather the overreliance on the feeling dopamine can stimulate.

Whilst craving a sugary snack may not be the best for our health, it is relatively safe in moderation. However, there are other things that can potentially be more harmful to us that can also be reinforced through dopaminergic activity. Theories of substance addiction suggest that dopamine can act to deepen addiction behaviours as individuals seek the feel-good rush it can stimulate. But this repeated use often means that we don’t get the same dopamine kick as before. It can then feel like we need to eat more sugar – or have it more frequently – in order to feel as good. We might also find that the other things we like to eat no longer give us pleasure, meaning that we need a sweet treat every day in order to feel good. Replace sugar with heroin and cocaine, and this dopaminergic surge can be a recipe for addiction. 

But what does this have to do with the nucleus accumbens?

Nucleus accumbens as dopamine centre

Research shows that the nucleus accumbens has a key role in the dopamine system. This is because it is part of the circuit in the brain linked with ‘reward-seeking in response to reward-predictive cues.’ The release of dopamine in the nucleus accumbens is ‘essential for the normal functioning of this circuit.’ This means that if the nucleus accumbens too much (or not enough) dopamine, our reward-seeking behaviour can be significantly impacted. This can mean that we experience the symptoms of dopamine deficiency, or experience an excess of the neurotransmitter. 

Dopamine deficiency can lead to:

• Depression
• Anxiety 
• Mood swings 
• Low libido
• Low motivation 
• Difficulty sleeping 
• Difficulty concentrating 
• Poor memory 
• Gut issues 

This can lead to an increase in reward-seeking behaviour as a way of ‘self-medicating’ to feel better. When we are stressed, this unfortunately often takes the form of a maladaptive coping mechanism, such as binge eating, heavy drinking or drug use. This can then lead to a reinforcement of negative behaviour patterns that can risk the development of addiction.

In contrast, an excess of dopamine could cause:

• Psychosis 
• Aggression 
• Outburst of energy 
• Difficulty sleeping 
• Hallucinations 

This is sometimes known as ‘dopamine overdose’ and can lead to a range of distressing psychological symptoms. 

As aforementioned, the nucleus accumbens sits at the centre of our dopamine circuits. This means that any imbalance in this brain region can dramatically affect our neurotransmitter levels and, therefore, our overall mental health. Dopamine levels can be regulated through healthier means, such as:

• Meditation 
• Self-care 
• Good nutrition 
• Sufficient sun exposure 
• Good sleep hygiene 
• Positive socialisation 

Dopamine levels can also be addressed through forms of medically assisted treatment. These forms of treatment are often offered for individuals dealing with depression and anxiety alongside addiction difficulties. This two-pronged treatment can first help address any physiological contributions to dopamine imbalance. It can also provide you the opportunity to discuss your experiences with a specialist therapist in the group, 1-1 or psychotherapy. This can allow you to investigate any underlying issues as well as provide an opportunity to learn ways to deal with both acute and chronic stress in the interest of longer-term management of emotional distress in the future.