Tag Archives: Pleasure

Pain impairs our ability to feel pleasure — and now we know why, and how

Researchers are homing in on the brain circuits that handle pain-induced anhedonia, the reduction in motivation associated with experiencing pain. The findings, currently only involving lab rats, might prove pivotal in our efforts to address depression and the rising issue of opioid addiction.

Pain is definitely not a sensation most of us are excited to experience. And although physical hurt is obviously unpleasant, it isn’t the only component of this sensation. Affective pain can be just as debilitating, and much more insidious. New research has identified the brain circuits that mediate this kind of pain, in a bid to counteract its long-term effects — which can contribute to the emergence of depression and make people vulnerable to addictions that take that pain away, such as opioid use disorder (OUD).

Show me where it hurts

Chronic pain is experienced on many levels beyond just the physical, and this research demonstrates the biological basis of affective pain. It is a powerful reminder that psychological phenomena such as affective pain are the result of biological processes,” said National Institute on Drug Abuse (NIDA) Director Nora D. Volkow, M.D, who was not affiliated with this study.

“It is exciting to see the beginnings of a path forward that may pave the way for treatment interventions that address the motivational and emotional effects of pain.”

Pain, the authors explain, has two components: a sensory one (the part you can feel) and an affective, or emotional, component. Anhedonia — an inability to feel pleasure and a loss of motivation to pursue pleasurable activities — is one of the central consequences of affective pain. Considering the strong links between anhedonia, depression, and substance abuse, the NIDA has a keen interest in understanding how our brains produce and handle affective pain.

Previous studies found that rats in pain were more likely to consume higher doses of heroin compared to their peers. In addition to this, they lost a sizable chunk of their motivation to seek out other sources of reward (pleasure), such as sugar tablets.

The current paper built on these findings, and aimed to see exactly how this process takes place in the brain. The team measured the activity of dopamine-responding neurons in a part of the brain’s “reward pathway” known as the ventral tegmental area. This activity was measured while the rats used a lever with their front paw to receive a sugar tablet. In order to see what effect pain would have on the activity of these neurons, rats in the experimental group received an injection that produced local inflammation in their hind paw. Rats in the control group were injected with saline solution.

After 48 hours, the researchers noted that rats in the experimental group pressed the lever less than their peers, indicative of a loss of motivation. They also saw lower activity levels in their dopamine neurons. Further investigations revealed that these neurons were less active because the sensation of pain was activating cells from another region of the brain known as the rostromedial tegmental nucleus (RMTg). Neurons in the RMTg are, among other tasks, responsible for producing the neurotransmitter GABA, which inhibits the functions of dopamine neurons.

Despite this, when the authors artificially restored functionality to the dopamine neurons, the effects of pain on the reward pathway was completely reversed and the rats regained the motivation to push the lever and obtain their sugar tablet even with the sensation of pain.

In another round of lab experimentation, the team were able to reach the same effects by blocking the activity of neurons which produce GABA in response to pain. The rats who were part of this round of testing were similarly motivated to pick a solution of water and sugar over plain water even when experiencing pain. This, the authors explain, shows that the rats were better able to feel pleasure despite also experiencing pain.

All in all, even though the findings are valuable in and of themselves, the team says that this is the first time a link has been established between pain, an increase of activity of GABA neurons, and an inhibitory pathway effect in the reward system which causes decreased activity of dopamine neurons.

“Pain has primarily been studied at peripheral sites and not in the brain, with a goal of reducing or eliminating the sensory component of pain. Meanwhile, the emotional component of pain and associated comorbidities such as depression, anxiety, and lack of ability to feel pleasure that accompany pain has been largely ignored,” said study author Jose Morón-Concepcion, Ph.D., of Washington University in St. Louis.

“It is fulfilling to be able to show pain patients that their mental health and behavioral changes are as real as the physical sensations, and we may be able to treat these changes someday,” added study author Meaghan Creed, Ph.D., of Washington University in St. Louis.

The paper “Pain induces adaptations in ventral tegmental area dopamine neurons to drive anhedonia-like behavior” has been published in the journal Nature Neuroscience.

What’s the link between music, pleasure, and emotion?

A bad day can be made better with the right jam, and a boring commute is that much more enjoyable with your favorite tune in the background. But why does music have such a powerful impact on us? And why do we like it so much?

Image via Pixabay.

We know that music has a special significance to humanity, as it’s popped up (either independently or through a cultural exchange) in virtually every society in history. We experience that special significance daily when we put our headphones on or relax after work with a nice record.

Back in 2001, researchers at the McGill University in Montreal used magnetic resonance imaging (MRI) to show that people listening to music showed activity in the limbic and paralimbic brain areas, which are related to the reward system. This reward system doles out dopamine, which makes us feel pleasure, as a reward for sex, good food, and so on. Addictive drugs also work by coaxing the production and release of dopamine in the brain.

That being said…

We don’t really know why, to be honest

But we do have a number of theories.

Back in his 1956 book Style and Music: Theory, History, and Ideology, philosopher and composer Leonard Meyer proposed that the emotional response we get from music is related to our expectations. He built on previous theories (the belief-desire–intention model) that the formation of emotion is dependent on our desires. The inability to satisfy some desire would create feelings of frustration or anger but, if we do get what we want, we get nice feelings as a reward. Delayed gratification also makes an appearance here: the greater the split between frustration and when we actually get what we want, the better we will feel once we get it, the theory goes.

In Meyer’s view, because music works with patterns, the human brain subconsciously tries to predict what the next note or groups of notes will be. If it’s right, it gives itself a shot of dopamine as a reward. If it’s not, it will try harder, and get a higher shot of dopamine once it eventually succeeds. In other words, simply having an expectation of how the song should go makes it elicit emotions in our brain, regardless of whether that expectation proves to be right or not.

It’s a nice theory, but it’s very hard to test. The main issue with it is that music can be so diverse that there are virtually endless ways to create and/or go against expectations, so it’s not exactly clear what we should test for. A song can rise or fall quickly, and we may expect a rising song to continue to rise — but it can’t do that indefinitely. We know jarring dissonances are unpleasant, but there also seems to be a cultural factor in play here: what was top of the charts two thousand years ago may sound completely horrendous today. You can listen so some reconstructions of ancient music here and here.

Expectations are in large part driven by how a particular piece we’re listening to has evolved so far, how it compares to similar songs, and how it fits in with all the music we’ve listened to so far. We all have our own subconscious understanding of what music ‘should be’ and it is to a large degree driven by our culture. This is why jazz, a melting pot of musical genres and methods, first sounds a bit off to those unacquainted with it.

Music also seems to have a physiological effect on humans. Past research has shown that our heartbeats and breathing patterns will accelerate to match the beat of a fast-paced track “independent of individual preference”, i.e. regardless of whether we ‘like’ the song. It’s possible that our brains interpret this arousal as excitement through a process called brainwave entertainment.

One other possibility is that music activates the regions of the brain that govern and process speech. As we’re very vocal and very social beasts, we’re used to conveying emotion via speech. In this view, music acts as a specific type of speech and as such can be a vehicle for transmitting emotion. Because we have the tendency to mirror the emotions of others, the song would end up making us ‘feel something’.

Music is a very rich playground — it may very well prove to be infinite. Our enjoyment of it also hinges on a very large number of very subjective factors, further complicating attempts to quantify the experience.

From a scientific point of view, it’s very interesting to ask why music sends chills down our spine. From a personal point of view, however, I’m just very thankful that it can.

Music statues.

Unexpected notes make music more enjoyable

Unexpected but consonant notes in music activate the reward centers in our brains, new research reveals.

Music statues.

Image via Pixabay.

Doesn’t that unexpected, but perfect, note peppered into a song send shivers down your spine? You’re not alone. New research at the McGill University shows that a dash of the unexpected in music lights up our brain’s reward centers, and helps us learn about music as we listen.

Unexpected by not unpleasant

The team, led by PhD candidate Ben Gold, worked with 20 volunteers through a musical reward learning task. The task consisted of a game where participants had to pick a color and then a direction. Each choice had a certain probability of returning a consonant (pleasurable) musical excerpt or a dissonant (unpleasurable) one.

Over time, participants started to learn which choices were more likely to produce either of these excerpts, which was what the team wanted. The test was designed to create an expectation in the mind of participants — either for musical dissatisfaction or enjoyment. Each participant had their brain activity measured using functional magnetic resonance imaging (fMRI) during the trial.

Pooling all this data together, the team determined reward prediction error for each choice the participants made. This error is the difference between expected reward and the actual outcome of their choice. Comparing these errors to MRI data revealed that reward prediction errors correlated with activity in the nucleus accumbens (NA), a brain region previously studies linked to feelings of musical pleasure. This is the first evidence that musically-elicited reward prediction errors cause musical pleasure, the team writes, as well as the first time an aesthetic reward such as music has been shown to create this kind of response. Previous studies have found similar results, but they worked with more tangible rewards such as food or money.

Finally, the team explains that subjects whose reward prediction errors most closely mirrored activity in the NA learned which choices lead to consonant tones faster than their peers. This, the team writes, establishes music as a neurobiological reward capable of motivating learning. The pleasurable feeling elicited by this effect motivates us to listen again and again, they explain, which helps us learn.

“This study adds to our understanding of how abstract stimuli like music activate the pleasure centres of our brains,” says Gold. “Our results demonstrate that musical events can elicit formally-modeled reward prediction errors like those observed for concrete rewards such as food or money, and that these signals support learning. This implies that predictive processing might play a much wider role in reward and pleasure than previously realized.”

The paper ” Musical reward prediction errors engage the nucleus accumbens and motivate learning” has been published in the journal Proceedings of the National Academy of Sciences.