science

Mesolimbic pathway

Mesolimbic pathway is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Mesolimbic pathway rather than just read about it. In short: The mesolimbic pathway, sometimes is referred to as the reward pathway, is a dopaminergic pathway in the brain. The pathway connects the ventral tegmental area in the midbrain to the ventral striatum of the basal ganglia in the forebrain.

Key takeaways

Mesolimbic pathway belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Mesolimbic pathway to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Mesolimbic pathway from memory before moving on to harder problems.

Reference excerpt

The mesolimbic pathway, sometimes is referred to as the reward pathway, is a dopaminergic pathway in the brain. The pathway connects the ventral tegmental area in the midbrain to the ventral striatum of the basal ganglia in the forebrain. The ventral striatum includes the nucleus accumbens and the olfactory tubercle. The release of dopamine from the mesolimbic pathway into the nucleus accumbens regulates incentive salience (e.g. motivation and desire for rewarding stimuli) and facilitates reinforcement and reward-related motor function learning; it may also play a role in the subjective perception of pleasure. The dysregulation of the mesolimbic pathway and its output neurons in the nucleus accumbens plays a significant role in the development and maintenance of an addiction.

Anatomy

The mesolimbic pathway is a collection of dopaminergic (i.e., dopamine-releasing) neurons that project from the ventral tegmental area (VTA) to the ventral striatum, which includes the nucleus accumbens (NAcc) and olfactory tubercle. It is one of the component pathways of the medial forebrain bundle, which is a set of neural pathways that mediate brain stimulation reward. The VTA is located in the midbrain and consists of dopaminergic, GABAergic, and glutamatergic neurons. The dopaminergic neurons in this region receive stimuli from both cholinergic neurons in the pedunculopontine nucleus and the laterodorsal tegmental nucleus as well as glutamatergic neurons in other regions such as the prefrontal cortex. The nucleus accumbens and olfactory tubercle are located in the ventral striatum and are primarily composed of medium spiny neurons. The nucleus accumbens is subdivided into limbic and motor subregions known as the NAcc shell and NAcc core. The medium spiny neurons in the nucleus accumbens receive input from both the dopaminergic neurons of the VTA and the glutamatergic neurons of the hippocampus, amygdala, and medial prefrontal cortex. When they are activated by these inputs, the medium spiny neurons' projections release GABA onto the ventral pallidum.

Function The mesolimbic pathway regulates incentive salience, motivation, reinforcement learning, and fear, among other cognitive processes. The mesolimbic pathway is involved in motivational cognition. Depletion of dopamine in this pathway, or lesions at its site of origin, decrease the extent to which an animal is willing to go to obtain a reward (e.g. the number of lever presses for intravenous nicotine delivery in rats or time spent searching for food). Dopaminergic drugs are also able to increase the extent an animal is willing to go to obtain a reward. Moreover, the firing rate of neurons in the mesolimbic pathway increases during anticipation of reward, which may explain craving. Mesolimbic dopamine release was once thought to be the primary mediator of pleasure, but is now believed to have only a minor or secondary role in pleasure perception.

Clinical significance

Mechanisms of addiction The mesolimbic pathway and a specific set of the pathway's output neurons (e.g. D1-type medium spiny neurons within the nucleus accumbens) play a central role in the neurobiology of addiction. Drug addiction is an illness caused by habitual substance use that induces chemical changes in the brain's circuitry. An addictive drug is defined as a substance that affects the mesolimbic system directly or indirectly by increasing extracellular levels of dopamine. Common addictive substances such as cocaine, alcohol, and nicotine have been shown to increase extracellular levels of dopamine within the mesolimbic pathway, preferentially within the nucleus accumbens. The mechanisms by which these drugs do so vary depending on the drug prototype. For example, cocaine precludes the re-uptake of synaptic dopamine through blocking the presynaptic dopamine transporter. Another stimulant, amphetamine, reverses the dopamine transporter and induces the release of dopamine from synaptic vesicles. Non-stimulant drugs typically bind with ligand-gated channels or G protein-coupled receptors. Such drugs include alcohol, nicotine, and tetrahydrocannabinol (THC).

These dopaminergic activations of the mesolimbic pathway are accompanied by the perception of reward. This stimulus-reward association shows a resistance to extinction and creates an increased motivation to repeat that same behavior that caused it. Additionally, drug intake changes synaptic plasticity in the ventral tegmental area and the nucleus accumbens. Repeated exposure to the drug can lead to lasting changes in the brain that gives rise to addictive behavior.

Relation to other neurological and psychological disorders The mesolimbic pathway is implicated in schizophrenia, depression, and Parkinson's disease. It is also theorized to be implicated in overuse of digital media, although it could simply be a consequence of a sedentary lifestyle. Each involves distinct structural changes within the mesolimbic pathway.

Other dopamine pathways

Mesocortical pathway Nigrostriatal pathway Tuberoinfundibular pathway

See also Antipsychotic Tardive dyskinesia Tolerance Withdrawal Motivational salience Apathy Abulia Akinetic mutism

References

External links

Worked examples

Example 1 — a first encounter with Mesolimbic pathway

Start with the simplest possible case. Write down what Mesolimbic pathway claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Mesolimbic pathway before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Mesolimbic pathway ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Mesolimbic pathway

In research: Mesolimbic pathway appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Mesolimbic pathway in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Mesolimbic pathway is common in secondary-school and first-year university syllabi. It links to neighbouring topics Addiction, Central nervous system pathways, Dopamine, so understanding it makes those chapters shorter.
In everyday life: Look for Mesolimbic pathway outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Mesolimbic pathway in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Mesolimbic pathway means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Mesolimbic pathway out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Mesolimbic pathway in simple terms?

Why does Mesolimbic pathway matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Mesolimbic pathway?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Mesolimbic pathway.