Neuroscience news block: weed, predictive processing and seeing your brain activity in real time!

The last month brought a lot of neuroscience news, some were joyful (for people with anxiety) and some less so (for weed connoisseurs). Still, one thing they had in common: all of them were exciting. 

If your mom read the recently published studies about marijuana effects on the brain she would certainly say “I told you so!”. These studies are not really encouraging: one shows neural networks being disrupted1 and the other one -- rats getting lazy2, all at the hands of THC. The disrupt of neural circuits, scientists from Osaka University have found, is caused by cannabinoids unnecessarily cutting off essential neural connections. Normally, as we grow older some connections in our brain get eliminated, a neural spring cleaning of sorts, leaving only the most efficient and productive connections behind. One of the important chemicals responsible for that seem to be endocannabioids, produced in our own body3,4,5. Now this is all fine and dandy when it happens in the natural and intended way. However, THC from a joint or a muffin seems to result in a similar regression, just that this time actually important and hard-working connections get cut off leading to gaps in neural circuits. Another study showed that rats on weed (contact me if you want this as a band name) became cognitively lazy. When sober, rats preferred to complete a more difficult task that resulted in two sugar pallets. After being drugged, however, they favoured solving an easier challenge and ignored the more demanding task despite the bigger reward it offered. They still were able to solve the difficult task, they just couldn’t be bothered to do it anymore. The study authors suggested that THC affected the motivation to use their cognitive abilities, but not the intelligence itself. All of this merely shows that in the current wave of legalization it is but wise to keep researching weed’s influences on the brain in order to get a full picture.

But you know, it’s just, like, your opinion, man. From https://img1.etsystatic.com/049/0/9283235/il_570xN.713530825_tbze.jpg

But you know, it’s just, like, your opinion, man. From https://img1.etsystatic.com/049/0/9283235/il_570xN.713530825_tbze.jpg

Much better news are reserved for people with anxiety or PTSD. A new study6 has found that there might be an easier way to shut up the nagging anxiety voice inside your head than popping Xanax or taking hundred hours of therapy. In this study, the participants were using a technique called “neurofeedback”, meaning you get an actual real-time feedback on what is going on in your brain (in form of a sound, movie or even a video game). In this case, the received feedback represented the current level of activity in their amygdala, a small region responsible for processing different emotions, most prominently fear. The amazing thing was that the participants were able to control this activity using the power of their minds (not Professor X-style though). In the course of the experiment they managed to consciously quiet their amygdala while constantly receiving feedback of how active it is in any given moment. This was achieved by putting the participants inside an MRI scanner and making them look silly by making them wear an electroencephalogram (EEG) cap on their heads. These methods were combined in order to get a precise EEG “fingerprint” showing how active the amygdala is. People were then either shown a video of a person skateboarding or just listened to a sound, with the speed of the skateboard and the loudness of the sound being determined by the level of the amygdala activity. The participants then trained to alter the sound and the speed by deliberately reducing this activity with any methods they found helpful. In an additional experiment the scientists showed that downregulating amygdala also helps with emotional regulation on the behavioral level. Although it is amazing to see how people are able to gain control over their emotions it is still to be tested on patients actually suffering from anxiety disorders. But the results are nevertheless quite promising as neurofeedback seems to be an effective and inexpensive addition to current treatment strategies.

Control your emotional responses with your mind power! Image by TomaTheSpook.

Control your emotional responses with your mind power! Image by TomaTheSpook.

The last piece of news I want to talk about shows that what you think you see is sometimes not what you actually see (#deep). How often have you found yourself in an awkward situation after not noticing your spouse’s new hairdo or your friend’s fancy new glasses? I bet the answer is more than zero. The quite elaborate study published in Nature Neuroscience suggests that there is a biological basis to it rather than sheer lack of interest7. It was found that after a mouse was presented with a certain situation for a couple of times certain neurons in its visual cortex started to predict what will be seen in this clear defined situation. Essentially, basing on the previous experience the brain made a model of the situation and started to predict how its details will look like right before seeing it. Specifically, mice were trained to navigate in a tunnel with different patterns on the walls. After a while some neurons started to fire in specific ways dependant on which wall pattern the mouse was about to reach next. By looking at this cell activity you could actually predict what the mouse expects to see! It wasn’t exactly a secret that our perception relies on our expectations as much (if not even more sometimes) than on what actually is out there in the real world8,9,10,11 but it is a nice addition to the growing body of evidence. So if you have your internal model of your wife, these expectations might dominate your perception and let the new glasses slide out of it. Use this as an excuse this time, this will make quite a nice save. (Our brain acting like a predictive machine is a notion of a paradigm called predictive coding which is incredibly interesting and I’ll write about it at some point soon. Meanwhile you can read up on it here and here.)

I'd still rather go with the scientific excuse.

I'd still rather go with the scientific excuse.

Sources:
1,2 (marijuana studies) 
3, 4, 5 (endocannabinoids)
6 (neurofeedback)
7 (mice predicting visual stimuli)
8,9,10,11 (interactions of expectation and perception)