Pornography, a closer look

Come see, come see, it’s all over the internet and it’s called pornography!

Ever since the widespread availability of pornography caused by the internet, its usage has skyrocketed. Estimations of porn consumption put it between a range of 50-99% in men and 30-86% in women. This indicates that many of us are familiar with pornographic content. While opinions on porn are divided, so are the research findings. After the legalization of porn in Denmark in 1969, there was a reduction in the reported sexual aggression. Thus, when looking at the advantages and disadvantages, one could argue that watching porn can be a safe recreational outlet which could even decrease sexual harassment or assault. However, there are also those who argue that consuming porn can lead to reduced relationship quality, sexual addiction or even could encourage sexual aggression. It’s just not all that simple when it comes to the effects of porn. As an example, researchers reported that for men, using porn would on average lead to reduced sexual intimacy, while for women the opposite was found. The researchers hypothesize that this finding could likely be explained by men tending to watch porn alone more, whereas women would be more likely to watch it in a shared experience. Furthermore, the kind of porn that men are attracted to on average lacks context, whereas women are on average more interested in softer forms with a storyline. 

The research on pornography & our brain is having trouble getting started

The amount of research conducted on the effects of porn consumption on our brain is rather sparse, and I have to say that it’s hard to filter through the articles I encountered. One reason is, that from the limited number of publications, another reason is the limitations that many studies have, where one of the biggest is the small sample sizes used.

Consumption versus addiction

It’s important to state that there is a difference in the effects of porn based on the frequency it’s consumed at. A small subgroup of porn consumers watches porn on a daily basis and has a hard time kicking that habit. Men who suffer from porn addiction are more likely to withdraw emotionally from their relationship and are at an increased risk for developing depression. Since porn is watched by men to a much greater extent, the studies that focus on excessive use are often limited to samples with only men.

Our brain & porn

What happens in our brain when we watch pornographic content? For this part, I want to reintroduce the dopaminergic system. Dopamine is a hormone/neurotransmitter that has an important function in reward processing and evaluation. Certain activities or consumptions can increase our dopamine level, making it higher than baseline for a transient amount of time. When we eat chocolate, there will be a brief spike in dopamine, it spikes to an amount 50% higher than baseline. When we have sex, dopamine will rise to around twice the baseline level. We can imagine that if pornography lies close to this doubling of dopamine levels, the feeling of wanting to watch porn is then rooted in something very rewarding. The problem with repeatedly watching porn is that the high dopamine release will make it harder for different interactions (e.g. sex) to raise dopamine levels to equal or higher than the level caused by the porn consumption. This  can potentially cause numbness to the dopaminergic response due to the inability of other factors to compete with or overthrow the effects of porn consumption. Therefore, excessive porn consumption may lead to difficulties in motivation and goal pursuit and affect daily-life romantic relationships or sexual interactions. 

When we look at the brain of people who consume pornography excessively, impairments in executive functioning and working memory may be found, likely through altered activity in an area crucially involved in these functions: the dorsolateral prefrontal cortex. One way to obtain information about the brain exposed to pornography is to correlate hours of watching porn per week with gray matter volume. Researchers who investigated this for the caudate (among other functions, important for processing visual information, movement control, working memory and emotions and cognitive functions) and putamen (among other functions, involved in reward and addiction) saw a reduced volume in the right caudate and left putamen with increasing hours of porn watched weekly. Furthermore they used functional MRI (fMRI) to investigate the connectivity and revealed that higher consumption of pornography was associated with a reduced connectivity of the left putamen and right caudate to the left dorsolateral prefrontal cortex. As I mentioned earlier, such studies investigating the effects of pornography on the brain are still sparse, in need of reproduction and larger sample sizes to draw more solid conclusions. 

Take away message:

While many of us consume porn without problems, some people develop addictive tendencies which can have a negative impact on their life. While the effects of consumption are still under investigation, it seems that porn can have a negative effect on our dopaminergic system when used at high frequency and/or intensity. Thus, if you like watching porn regularly, try alternating it a bit with some delicious dark chocolate or sex.

Author: Kobus Lampe
Image created using DALL-E-2 open AI software


Serotonin = happy?

As you may know depression is one of the most common mental health disorders and affects millions of people globally. Either you or someone around you will likely struggle with it in your lives. One basic idea that seemed certain for a long time is that this disorder is associated with abnormally low serotonin in the brain. However, a recent umbrella review incorporating results from several dozen studies has shed new light on this assumption.

But let’s start from the beginning. Serotonin is a neurotransmitter in your brain that is linked to many functions, such as the cognition, reward, learning, memory, and even bodily processes such as vomiting. Most likely you have heard about people with depression (or more specifically MDD, major depressive disorder) having brain serotonin levels that are too low. And indeed, one of the roles that serotonin plays is in the regulation of our moods. However, given many recent research publications, the idea of MDD patients having low serotonin is actually questioned by more and more scientists. Of course, whether serotonin is an important component in depression also affects how we think about the effectiveness of SSRIs (‘selective serotonin reuptake inhibitors’), the major pharmacological treatment of depression. So, the authors of an umbrella review published in 2022 set out to collect as much relevant evidence as possible to figure out whether there is a connection between serotonin and depression after all.

An umbrella review is essentially a meta-analysis of several meta-analyses; and a meta-analysis is just a study where several studies’ results on the same topic are combined and compared. Essentially, what they investigated was whether people with depression have lower serotonin levels or activity than healthy people. To test this, they analyzed data from several studies where serotonin or its major metabolite (a basic building block of serotonin) were measured in blood samples of participants. Combined results from 21 individual studies were that depressed patients really didn’t have lower serotonin levels than healthy individuals.

If you’re already somewhat familiar with the brain and its neurotransmitters, you may suspect that the picture is actually a bit more complicated than just measuring how much serotonin someone has in their brain! Maybe you have read our database articles on the synapse and serotonin, and know that how many (auto)receptors you have for a certain neurotransmitter can impact how much of this neurotransmitter is available in your brain. Thus, if you have more or less serotonin receptors, more or less serotonin becomes available to your neurons, even though the amount of serotonin in your brain doesn’t actually change. Well, the authors of the umbrella review were definitely well informed of this effect. But even after consulting many more studies, they found that there were alsol really no major differences between healthy and depressed people regarding serotonin receptors. Other factors that can determine serotonin availability are the amount of serotonin transporters at the synapse, and certain genetic differences. For these factors also no relation was found with depression!

Wow, so where did this idea of low serotonin and depression come from then? Well, a significant relationship that the umbrella review did find is that the use of SSRIs, both for people with and without depression, was associated with generally lowered serotonin levels. Plus, the authors caution that many of the meta-analyses and studies they read on a daily basis do not control for the medication use of their subjects. That is, they do not select only patients that are either taking or not taking medication. Therefore, this may have skewed the results of many older studies on the topic, and might have led to the false link between depression and low serotonin. Even worse, this may still be going on in entirely different research looking into other mental disorders.

So, remember kids, always control for medication use in your empirical pathology studies!

Author: Melanie Smekal


A fish with a tiny brain

A human's brain contains about 100 billion neurons that are interconnected in many ways. This makes it rather complicated to study. It would be handy for scientists if there was a smaller and simpler brain to work with. Fortunately, there is: the brain of a zebrafish.

Zebrafish are small, striped, tropical fish. They have become increasingly popular in scientific research in recent years. Mainly because zebrafish are related to humans: they are both vertebrates and 70% of the genes in a zebrafish have a corresponding gene in humans. As a result, a zebrafish can suffer from the same diseases, such as Parkinson's. In addition, zebrafish are easy to maintain and very suitable for genetic modification. Thus, the zebrafish is an excellent candidate for brain research.

The brain of a young zebrafish is smaller than one cubic millimetre and contains about 100 thousand neurons. Human brains, by comparison, are 10 million times bigger. Because young zebrafish are transparent, scientists can use a very precise method to measure their brain activity. This method is called "light sheet fluorescence microscopy". This is a hefty term, but thankfully, it can be divided into three pieces:

1. "Microscopy"

Microscopy simply means: Looking at something that cannot be seen with the naked eye.

2. "Light sheet"

To see the brain cells, a flat laser is shone through the transparent fish. With this, a layer of the brain can be illuminated very precisely, at the cell level. Thus, the entire brain can be illuminated by the laser, layer by layer, in a single second.

3. "Fluorescence"

The calcium ions in brain cells are made fluorescent. As a result, they emit light when shone upon by the laser. A brain cell normally contains very few calcium ions. But when the brain cell activates, a lot of calcium ions flow in. So by measuring calcium ions, you also measure brain activity!

With this amazing technique, the brain of a zebrafish can be mapped down to the brain cell. This will give science a better understanding of the zebrafish, and more importantly the brain.

Author: Boudewijn van Gils


WTF is consciousness?

Hey you! Yes, you! Are you conscious right now? Of course you are, right? But what does this actually mean? 

Consciousness is an extremely intuitive, yet mysterious phenomenon: for scientists, philosophers and really anybody else. It quite literally entails everything we experience; yet nobody is sure how it really occurs. Maybe you have asked yourself before if the way you perceive the color orange is the same way that other people do. Or maybe you have asked yourself how you can be sure that other people are conscious at all. While in everyday life it mostly helps to assume that people have similar conscious experiences to you, these are actually questions to which we have no clear answers …

Generally, consciousness can be thought of as having two aspects: functional and phenomenal. Functional consciousness includes all the data we can collect about someone’s conscious experience; for example, we can measure neuronal firing. So this is pretty objective, but often doesn’t tell us all that much about someone’s direct experience: You can’t tell how Petra perceives the color orange from her EEG scan. Phenomenal consciousness is where it gets juicier: It is the subjective nature of experience of a person. Thus, we can say that a person, animal or other life form is conscious if there is ‘something it is like’ to be them. For example, there is something it is like to see the color orange, to feel happy or to think a thought. These ‘what-it-is-like’s’ are also called qualia and they are arranged into larger (‘eidetic’) structures, e.g. what it is like to see an orange at the market. 

Picture: The quale (singular of ‘qualia’) of the color orange (left) is included in the eidetic structure of seeing oranges at the market (right).      

So what about the brain then? Assuming that consciousness originates here (which neuroscientists tend to do), how does this work?

Well, it’s a bit complicated: Researchers have thought of all sorts of different experiments to learn about consciousness in the brain. One example is the use of ‘binocular rivalry’. Essentially, when you show different images to the left and right eye of someone, the visual perception of the person will switch between the left and right picture. So the visual input stays the same, while only the conscious experience (what you actually see) changes. (Importantly, in this experiment the participant cannot control which image they see, since both stimuli are competing to be perceived. So there is a difference between attention and your conscious perception, and here we are measuring the latter.) Now we can use an fMRI machine to localize a brain area that is more active when this perceptual switch occurs. Multiple studies have reported a whole network of areas, mostly in the right hemisphere being involved. Some researchers are especially interested in the role of frontal regions* in this switching process. 

A study from 2014 investigated what areas are involved in the change of perception in a new way: Unlike other studies that made participants report when a switch would take place, the researchers also added a condition where they inferred this switch from the pupils and eye movements. Comparing these conditions, interestingly frontal areas were only more active than usual when participants were asked to report switches, but not when these were inferred. Thus, frontal activation seems to be linked more to the active report and not to the actual change in perception. Other areas were still associated with the switch though, namely parietal and occipital regions*…

While this is pretty cool research in itself, it still begs the question of what this really tells us: Even if we find one or several areas where consciousness is located, we still don’t really know how consciousness is produced there in the first place. Obviously, much more research needs to be (and is being) done to figure this all out. 

As you can see, consciousness remains an exciting topic! We will soon feature more articles on other neuroscientific methods to investigate it, and what they mean for the philosophy of consciousness.

*Not sure what the frontal, occipital and parietal cortex do? Check out our Brain Basics 1.01 article, where you can learn some brain basics!

Links and references:

Author: Melanie Smekal