<p><strong>A bit of context</strong></p>

<p>In mammalian brains, a main neurotransmiter linked with reward is Dopamine. This molecule is produced in the Ventral Tegmental Area (VTA) and in the Substantia Nigra (SN).</p>

<p>In a very famous study, Schultz recorded neurons in this two regions (at the time, we didn't really make the difference between them), and realised that the activity of these neurons was linked with reward. More precisely, neurons were coding for Reward Prediction Error, a feature that is implemented in Reinforcement Learning models.</p>

<p>Recently, some researchers decided to adress your question.
To do this, they used <a href="https://en.wikipedia.org/wiki/Optogenetics" rel="nofollow noreferrer">optogenetics</a>, wich is a technique that permit you to modulate the activity of neurons with light.</p>

<p>You can read the paper here :
<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4241115/" rel="nofollow noreferrer">McNamara et al. Nat. Neurosci. (2014)</a></p>

<p><strong>What are the main results ?</strong></p>

<p>Mice with increased dopamine neuron's activity had better performance in a spatial task. They were <strong>better</strong> at learning a new maze. On top of that, the increased activity of VTA neurons induced a higher amount of specific oscillations (called Sharp Wave Ripples) in the Hippocampus, a structure important in spatial learning. We start to have strong evidence that this oscillations are important for memory, as disrupting them impair memory (see <a href="http://science.sciencemag.org/content/sci/336/6087/1454.full.pdf?casa_token=46waUdZ4ix4AAAAA:uQx-QkLtUb0psXkYr-sqNOl5I9YJATVce9-gP-lXqyFn7orFpy6CfTvEFW4O_p7Jv6cI9N5kwwxPETU" rel="nofollow noreferrer">Jadhav et al. Science (2012)</a> and <a href="http://www.its.caltech.edu/~bi250c/papers/Girardeau-2009.pdf" rel="nofollow noreferrer">Girardeau et al. Nat. Neuosci. (2009)</a> if you are interested in the subject)</p>

<p>Note that this study was done in mice. Their is probably papers making a link between the activity of the VTA and learning using FMRi on humans, but I don't know the litterature enough.</p>

CC BY-SA 4.0
2019-01-14T00:20:06.110Z
Thanks a lot! Do you happen to know if there are any studies on whether domapine increases plasticity at the synapse level? I.e. is a synapse more likely to grow/strengthen under higher dopamine concentration?
danijar
CC BY-SA 4.0
2019-01-14T11:22:20.030Z
@danijar You're welcome ! There is indeed evidence that dopamine modify the strength of synapses. More precisely, dopamine modify Long Term Potentiation, one of the main mecanism known to modify the strength of synapses (One exemple I just found : [S. Li et al Nat. Neurosci. (2003)](https://www.nature.com/articles/nn1049) . It is a really good question and I will edit my answer when I have time.
Hornycar
CC BY-SA 4.0
2019-01-09T17:37:02.260Z
2019-01-09T17:37:02.260Z
Hornycar
<p>The effect of dopamine signaling is one of the areas where computational neuroscience has provided insight into brain mechanisms, specifically via Reinforcement Learning (RL) models.</p>

<p>Based off <a href="http://mindmodeling.org/cogsci2013/papers/0580/paper0580.pdf" rel="nofollow">this paper</a> and <a href="https://uwspace.uwaterloo.ca/bitstream/handle/10012/8943/Rasmussen_Daniel.pdf" rel="nofollow">PHD thesis</a> from Dan Rasmussen, this first began with <a href="http://www.ncbi.nlm.nih.gov/pubmed/9658025" rel="nofollow">this publication from Schultz</a> showing that dopamine acts as a reward signaler. From the abstract:</p>

<blockquote>
  <p>Dopamine neurons are activated by rewarding events that are better
  than predicted, remain uninfluenced by events that are as good as
  predicted, and are depressed by events that are worse than predicted.
  By signaling rewards according to a prediction error, dopamine
  responses have the formal characteristics of a teaching signal
  postulated by reinforcement learning theories.</p>
</blockquote>

<p>To answer your question directly, it does seem the speed/plasticity of learning is modulated by dopamine neurons.</p>

CC BY-SA 3.0
2016-03-19T20:28:27.433Z
But also see [Friston et al., 2012](http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1002327) for a more general theory of dopamine function
mrt
CC BY-SA 3.0
2016-05-11T00:36:16.097Z
Thanks for your answer and sorry for the late reply. Do you conclude your last sentence from the cite above? I understand that dopamine is associate with reward. But that doesn't directly relate to whether high dopamine level means much learning and low dopamine level (or negative reward) means less learning, does it?
danijar
CC BY-SA 3.0
2016-05-11T16:27:47.800Z
@danijar you're correct. I've accidentally jumped a level in my induction. I'll try and fix that.
Seanny123
CC BY-SA 3.0
2016-03-19T15:46:03.913Z
2016-03-19T15:46:03.913Z
Seanny123
<p>The human brain is a signal processing system. Input streams contain sensory, motor, reward and possibly more signals mixed. I wonder if neuro transmitters associated with reward increase or decrease memorization of those streams. That would result in a tendency to memorize streams co-occurring with high reward over those co-occurring with low reward. Thus, attractors would settle for better streams and we would perform actions  optimizing the reward.</p>

CC BY-SA 3.0
2016-03-16T23:54:28.827Z
So are you asking for models that use neuro-transmitters associated with reward (such as dopamine) to drive learning?
Seanny123
CC BY-SA 3.0
2016-03-18T20:21:04.710Z
@Seanny123 That would be interesting as well. My question is whether there is biological evidence for faster learning or increased plasticity under e.g. dopamine emission.
danijar
<neuroscience><cognitive-neuroscience><neuro-transmitters><reward>
Is the amount of learning modulated by reward transmitters?
danijar
# Is the amount of learning modulated by reward transmitters?

(Asked by: username_0 on 2016-03-16)

The human brain is a signal processing system. Input streams contain sensory, motor, reward and possibly more signals mixed. I wonder if neuro transmitters associated with reward increase or decrease memorization of those streams. That would result in a tendency to memorize streams co-occurring with high reward over those co-occurring with low reward. Thus, attractors would settle for better streams and we would perform actions optimizing the reward.

**Tags:** neuroscience, cognitive-neuroscience, neuro-transmitters, reward

> **Comments:**
> **username_1**: So are you asking for models that use neuro-transmitters associated with reward (such as dopamine) to drive learning?  
> **username_0**: @username_1 That would be interesting as well. My question is whether there is biological evidence for faster learning or increased plasticity under e.g. dopamine emission.  

---

## 2 answers

### Answer by username_2 on 2019-01-09. Score: 2

**A bit of context**

In mammalian brains, a main neurotransmiter linked with reward is Dopamine. This molecule is produced in the Ventral Tegmental Area (VTA) and in the Substantia Nigra (SN).

In a very famous study, Schultz recorded neurons in this two regions (at the time, we didn't really make the difference between them), and realised that the activity of these neurons was linked with reward. More precisely, neurons were coding for Reward Prediction Error, a feature that is implemented in Reinforcement Learning models.

Recently, some researchers decided to adress your question.
To do this, they used [optogenetics](https://en.wikipedia.org/wiki/Optogenetics), wich is a technique that permit you to modulate the activity of neurons with light.

You can read the paper here :
[McNamara et al. Nat. Neurosci. (2014)](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4241115/)

**What are the main results ?**

Mice with increased dopamine neuron's activity had better performance in a spatial task. They were **better** at learning a new maze. On top of that, the increased activity of VTA neurons induced a higher amount of specific oscillations (called Sharp Wave Ripples) in the Hippocampus, a structure important in spatial learning. We start to have strong evidence that this oscillations are important for memory, as disrupting them impair memory (see [Jadhav et al. Science (2012)](http://science.sciencemag.org/content/sci/336/6087/1454.full.pdf?casa_token=46waUdZ4ix4AAAAA:uQx-QkLtUb0psXkYr-sqNOl5I9YJATVce9-gP-lXqyFn7orFpy6CfTvEFW4O_p7Jv6cI9N5kwwxPETU) and [Girardeau et al. Nat. Neuosci. (2009)](http://www.its.caltech.edu/~bi250c/papers/Girardeau-2009.pdf) if you are interested in the subject)

Note that this study was done in mice. Their is probably papers making a link between the activity of the VTA and learning using FMRi on humans, but I don't know the litterature enough.

> **Comments:**
> **username_0**: Thanks a lot! Do you happen to know if there are any studies on whether domapine increases plasticity at the synapse level? I.e. is a synapse more likely to grow/strengthen under higher dopamine concentration?  
> **username_2**: @username_0 You're welcome ! There is indeed evidence that dopamine modify the strength of synapses. More precisely, dopamine modify Long Term Potentiation, one of the main mecanism known to modify the strength of synapses (One exemple I just found : [S. Li et al Nat. Neurosci. (2003)](https://www.nature.com/articles/nn1049) . It is a really good question and I will edit my answer when I have time.  

---

### Answer by username_1 on 2016-03-19. Score: 2

The effect of dopamine signaling is one of the areas where computational neuroscience has provided insight into brain mechanisms, specifically via Reinforcement Learning (RL) models.

Based off [this paper](http://mindmodeling.org/cogsci2013/papers/0580/paper0580.pdf) and [PHD thesis](https://uwspace.uwaterloo.ca/bitstream/handle/10012/8943/Rasmussen_Daniel.pdf) from Dan Rasmussen, this first began with [this publication from Schultz](http://www.ncbi.nlm.nih.gov/pubmed/9658025) showing that dopamine acts as a reward signaler. From the abstract:

> Dopamine neurons are activated by rewarding events that are better
> than predicted, remain uninfluenced by events that are as good as
> predicted, and are depressed by events that are worse than predicted.
> By signaling rewards according to a prediction error, dopamine
> responses have the formal characteristics of a teaching signal
> postulated by reinforcement learning theories.

To answer your question directly, it does seem the speed/plasticity of learning is modulated by dopamine neurons.

> **Comments:**
> **username_3**: But also see [Friston et al., 2012](http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1002327) for a more general theory of dopamine function  
> **username_0**: Thanks for your answer and sorry for the late reply. Do you conclude your last sentence from the cite above? I understand that dopamine is associate with reward. But that doesn't directly relate to whether high dopamine level means much learning and low dopamine level (or negative reward) means less learning, does it?  
> **username_1**: @username_0 you're correct. I've accidentally jumped a level in my induction. I'll try and fix that.  

---

