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I think we can all agree that getting to work with our hands just feels good. Even if the job itself isn’t exactly enjoyable, it becomes a little bit better when you get to use your hands. It’s relaxing, calming, and perhaps even distracting in that you have nothing else on your mind other than the work in front of you.

The fact that working with your hands is satisfying is self-evident to many of us. However, it’s always nice to have a bit of science backing up what is “common” sense. I came across such science in an article written by a researcher named K. G. Lambert. Lambert asserts that working with your hands (among other things) is good for your mental health. In this article, I’ll explain why this is by giving an overview of Lambert’s paper and a simple explanation of what’s happening during the brain when you work.

The Relationship between Effort and Reward

The brain mechanism that causes the beneficial side effects of working with your hands is what Lambert calls the accumbens-striatal-cortical circuit. I’ll explain exactly what this is later and how it works. For now, I’m going to start off by explaining some of the psychology behind effort and reward.

In short, when you’re rewarded for work that you’ve done, the reward feels more salient, meaning that you feel the sense of reward more strongly. Conversely, when you receive a reward for no reason, the reward is not as salient. In fact, Lambert referenced a study involving money showing that “…saliency of the money… was greater when the money was earned rather than simply given to subjects.” There is a positive correlation between effort and the feeling of reward.

So what is reward? Beyond mere compensation, reward can be thought of as simply a pleasant feeling as a result of compensation. Ultimately, when you do something because you anticipate a reward, you’re really anticipating a good feeling. If you did something that resulted in a bad feeling, you’d be very unlikely to do it again. A negative feeling leads to abandonment of a behavior, while a good feeling reinforces a behavior. Within the brain, a lot of this has to do with a neurotransmitter called dopamine, which I’ll talk more about later.

Since I’ve talked about behavior reinforcement, I think it’s important to point out that that rewarding feeling, by itself, can have a dark side. Remember that reward reinforces behavior. So, if you get a sense of reward after doing something you shouldn’t, then that behavior has just become reinforced. Basically, this is what leads to a lot of bad habits and addictions. A full discussion of this is beyond the scope of this article, but I felt I’d be remiss to not mention it here.

Now that we have an idea of what reward is and that it makes you feel good, the question then becomes, “What’s the point?” Sure, feeling good… well, feels good. But beyond that, what practical benefit does it have? Based off what I said in the last paragraph, it seems it may actually be harmful. Well, Lambert’s paper focuses primarily on looking for treatments for depression outside of the pharmacy. Some of the symptoms of depression are “…learning difficulties, fatigue and slowness of movement, and altered emotions.” If one reverses or even completely overcomes depression, one also reverses these and other symptoms. So, by undertaking actions that have been shown to have a positive effect on mood, one can improve, among other things, his or her learning ability, energy levels, and, of course, emotional level.

Keep in mind that you don’t have to be clinically depressed to benefit from this information. Just as your body benefits from exercise even if you’re already relatively healthy, your brain benefits from effort-based rewards even if you’re already in a relatively good mood on average. In fact, Lambert’s article didn’t catch my eye because I’m interested in improving mood itself, but because I’m interested in the overall mental benefits resulting from improved mood, primarily improved learning ability.

The ability to obtain and retain information (i.e. learn) is the most important skill. Anything that helps improve it is worth pursuing in my book. Kit Learning is about hands-on learning by directly working with and building the things that you find interesting, instead of only reading about it or doing textbook problems. Implicit in this is the fact that you’ll be working with your hands. Now that we’ve briefly discussed Lambert’s paper, we see that there’s potentially a compounding effect when you learn with hands-on work. As you work on your projects, kits, and models, you’re learning about the topic at hand (whether that’s soldering a circuit or painting a model car), and working with your hands improves your ability to learn the topic.  

So how exactly does working with your hands improve mood and, thereby, learning ability? To answer that, let’s move onto the brain.

An Introduction to the Accumbens-Striatal-Cortical Circuit

Before I dig into the neuroscience, I want to mention two things: one, I’m not a neuroscientist. I read some studies on the brain so I could understand what’s going on, and then I connected the dots. All this is to say that there could be some mistakes. At the very least, it’s probably oversimplified. Two, if you don’t particularly care about how this system works, then you can skip this section. You won’t really lose anything in terms of actionable information.

To begin talking about the brain anatomy behind improved mood and working with your hands, we have to understand that thing I mentioned earlier, the accumbens-striatal-cortical circuit. This is a circuit of connected brain structures comprised of, among other things, the nucleus accumbens, striatum, and cerebral cortex. Let’s go over these structures one at a time, and then I’ll explain how they’re all connected.

The nucleus accumbens plays several important roles in the brain, but we’re most interested in its role in processing motivation and reward. Whenever you have a rewarding experience, the levels of the neurotransmitter dopamine are increased in the nucleus accumbens. (There’s more to it, but this simplistic explanation is enough for our purposes). The nucleus accumbens is part of the striatum. Specifically, the nucleus accumbens is in a part of the striatum called the ventral striatum.

Since the nucleus accumbens is part of the striatum, the two share common roles. However, the striatum as a whole (consisting of the dorsal and ventral striatum), is also heavily involved in planning and executing movements in response to a stimulus. Probably the simplest example of this is obtaining and eating food when you’re hungry. In case you haven’t connected the dots yourself yet, the nucleus accumbens, with its role in processing motivation and reward, can provide the impetus to undertake a physical action, such as eating. The significance of this will be explained later.

The cerebral cortex is the third component of the accumbens-striatal-cortical circuit. It is the outside layer of the brain. Here, we’re primarily interested in two parts of the cerebral cortex, called the motor cortex and the somatosensory cortex. Collectively, these are the sensorimotor cortex. The motor cortex, as the name suggests, is involved with your body’s movement. The somatosensory cortex is involved with receiving tactile information from your body (“somato” meaning body). The motor cortex processes output, while the somatosensory cortex processes input.

Now that you know the components involved in the accumbens-striatal-cortical circuit, let’s talk about how this circuit is linked together. The fully detailed description of this circuit is extremely complex (at least for me), so I’ve only written about the essentials. There is a few more brain structures involved as well, which I’ll describe as we come across them.

Anatomy of the Accumbens-Striatal-Cortical Circuit

This accumbens-striatal-cortical circuit involves two different pathways: the direct pathway, and the indirect pathway. Simply put, the direct pathway induces muscle movement and the indirect pathway inhibits muscle movement. The direct pathway is activated when you want to engage your muscles, such as when walking or picking up an object, and the indirect pathway is activated when you don’t want to move, such as when sitting still and relaxing. If not for the indirect pathway, the pathway that inhibits muscle movement, you’d have a lot of involuntary movements throughout your day. The direct and indirect pathways work together so that you can make controlled, smooth movements.

Both of these pathways make use of excitatory and inhibitory neurons, which, as their names suggest, excite or inhibit activation of a brain structure. Note that I said activation of a brain structure, not of muscle. The pathways themselves are responsible for muscle activation, and they each contain both excitatory and inhibitory neurons. As you’ll see later, an inhibitory neuron does not necessarily lead to muscle inhibition, and an excitatory neuron does not necessarily lead to muscle excitation. As with the pathways, these two types of neurons work together so that you can control your body’s movement. Both pathways start the same way, with the cortex projecting (i.e. sending information to) the striatum, specifically the dorsal striatum. (Remember, the nucleus accumbens is in the ventral striatum). From this point, the circuit either branches off into the direct or the indirect pathway. Let’s start with the direct pathway.

The Direct Pathway

The direct pathway, in short, is from the motor cortex, to the dorsal striatum, to the internal globus pallidus (GPi), to the thalamus, and back to the motor cortex. The connections between each of these structures contain either excitatory or inhibitory neurons. Starting from the top, the motor cortex is connected to the striatum via excitatory neurons. During movement, these excitatory neurons are activated, which causes the striatum to activate. The striatum is connected to the GPi via inhibitory neurons, so when the striatum is activated, it in turn sends inhibitory signals to the GPi. This causes the GPi to decrease in activity. The GPi is connected to the thalamus with inhibitory neurons, so when the GPi’s activity is decreased, its inhibitory signal to the thalamus is decreased, therefore allowing the thalamus to be more active. When the thalamus is more active, it sends more excitatory signals to the motor cortex, which are then sent on to the muscles to facilitate the body’s movement.

The key takeaways are that, within this circuit, the GPi’s purpose is to hinder the thalamus, and the thalamus’s purpose is to excite the motor cortex, thereby exciting the muscles. Therefore, when the striatum decreases the GPi’s activity, the thalamus’s activity is increased, which increases muscle activity.

There are two other brain components that have an influence on this circuit: the substantia nigra, and the subthalamic nucleus. The subthalamic nucleus sends excitatory signals to the substantia nigra, and the substantia nigra sends back inhibitory signals to the subthalamic nucleus in order to tell the subthalamic nucleus to stop sending it excitatory signals. It does this because the substantia nigra also sends dopamine to the striatum. The dopamine from the substantia nigra further activates the inhibitory signals originating from the striatum, going to the GPi. In short, the substantia nigra, activated by the subthalamic nucleus, also inhibits the GPi, thereby increasing movement. This is where our feel-good neurotransmitter comes in.

Now let’s go over the indirect pathway.

The Indirect Pathway

As with the direct pathway, the whole process starts when the motor cortex sends an excitatory signal to the striatum. From here, the circuit differs from the direct pathway. Instead of sending an inhibitory signal to the internal globus pallidus, as in the direct pathway, the striatum instead sends an inhibitory signal to the external globus pallidus (GPe). The GPe has an inhibitory connection to the subthalamic nucleus, so when the GPe is inhibited, the subthalamic nucleus increases in activity. Now, the subthalamic nucleus sends an excitatory signal to the GPi, which, opposite of the process in the direct pathway, causes the GPi to increase in activity, which causes it to send more inhibitory signals to the thalamus, in turn causing the thalamus to send fewer excitatory signals to the motor cortex, thereby decreasing movement.

Hand Movement

Look at this handsome fellow.

This is called the motor homunculus (there’s also a sensory homunculus that has similar proportions). The size of each of the homunculus’s body parts corresponds to the amount of motor control that our brain has devoted to that area. Notice how large the hands are compared to anything else on the homunculus’s body. They are, by far, the largest body part. This shows that there is more brain power devoted to control of our hands than to anything else. On the neurological level, this is shown by the fact that the hands are heavily innervated (meaning they have a lot of nerve fibers). Here’s a 2-D version of the motor homunculus, with each body part mapped to its respective region of the motor cortex:

Lambert concisely states the significance of this in her paper: “Considering the amount of brain area devoted to the sensitivity and movement of the hands, it is likely that behavior maximizing the use of the hands (requiring movement of arms/forelimbs, wrists, and fingers) may be the most engaging for the accumbens–striatal–cortical circuit.” Let’s break down why this may be the case, using what we’ve discussed so far.

Referring back to the description of the accumbens-striatal-cortical circuit, we see that the motor cortex is the impetus of the entire system for both the direct and indirect pathways. Seeing as the hands have a lot of cortical real estate devoted to them alone, I think it’s reasonable to conclude that the hands activate the accumbens-striatal-cortical circuit the most.

However, there’s a catch. In order to receive the most benefit, you have to consciously, deliberately use your hands in an effortful activity. To understand what this means, think of typing. I’m a relatively good typist, so as I sit here and type out this post, the actual typing process is pretty mindless. Even if you’re not a good typist, all you’re doing is pressing a series of buttons, which is hardly effortful. Lambert explains it this way: “[pushing buttons and typing] may not activate our brains to the extent observed in the more intricate and demanding manual tasks performed by various artisans across the world.” Now let’s refer back to our discussion of effort-based rewards. Earlier I said that you’re potentially receiving a compounding benefit when you work with your hands. I hope the reason for this has become more apparent. As you use your hands, dopamine from the substantia nigra is being sent to the nucleus accumbens. Remember that higher dopamine levels in the nucleus accumbens corresponds to good feelings. Now, combine that with the concept of effort-based rewards, which, in this context, means working with your hands on something you find fun and enjoyable. So you now have dopamine produced from the accumbens-striatal-cortical circuit and dopamine produced from just having fun. And if you’re working on something you find fun and educational, then the improved mood will increase your ability to learn.

Conclusion

Let’s review what we’ve learned. The circuit in the brain that provides the connection between movement and reward is the accumbens-striatal-cortical circuit. This circuit regulates movement by utilizing the direct and indirect pathways. These pathways excite and inhibit movement, respectively, so you can have smooth and controlled movements.

The nucleus accumbens is part of this circuit. The nucleus accumbens is a brain component that is heavily involved in processing reward and motivation. The presence of the neurotransmitter dopamine in the nucleus accumbens corresponds to improved mood, and improved mood can mean an increase in learning ability, as well as many other benefits. Dopamine in the nucleus accumbens is also involved in regulating movement. This is our connection between movement and improved mood.

The hands specifically cause the most activation of the accumbens-striatal-cortical circuit because the hands have a large portion of motor cortical real estate devoted to them. The motor cortex is the impetus for the accumbens-striatal-cortical circuit, so it follows that activating the largest part of the motor cortex results in the most activation for this circuit. Therefore, as the circuit becomes more active, more dopamine is released into the nucleus accumbens, thereby causing greater improvements in mood.

Alongside mood improvements resulting from moving your hands, there are also mood improvements brought about by simply doing something enjoyable. Tying into this is the idea of pursuing a specific goal, something with a well-defined result that you want and that you will achieve if you work for it.

As stated earlier, the nucleus accumbens is heavily involved in processing effort-based rewards. Now we combine all these ideas to say that using your hands in the pursuit of a goal potentially has a compounding effect. You receive the mood enhancing benefits of working with your hands, combined with the mood enhancing benefits of doing something enjoyable, combined with the mood enhancing benefits of doing something that produces a clear and desirable result. Put another way, pursue work and other manual tasks that you enjoy. Don’t only do something enjoyable (such as watching TV) and don’t only do something manual (such as fixing a broken object). Combine both into a single task whenever you can and reap the benefits.

Further Reading

Rising rates of depression in today’s society: Consideration of the roles of effort-based rewards and enhanced resilience in day-to-day functioning Kelly G. Lambert

The nucleus accumbens as a nexus between values and goals in goal-directed behavior: a review and new hypothesis Franceso Mannella, Kevin Gurney, Gianluca Baldassarre

The Nucleus Accumbens: A Comprehensive Review Sanjay Salgado, Michael G. Kaplitt

Similar Roles of Substantia Nigra and Ventral Tegmental Dopamine Neurons in Reward and Aversion Anton Ilango, Andrew J. Kesner, Kristine L. Keller, Garret D. Stuber, Antonello Bonci, Satoshi Ikemoto