Cerebellum and basal nuclei instead of a crystal ball: how the brain predicts the future
Today, you and I will move a little away from examining research on the basis of our favorite physics / chemistry and turn our attention to research on the human body. More precisely on the study of the brain. This body is so complex that all previous studies gave one answer and 10 new questions, so to speak. More specifically, today we are going to consider a study that intends to answer the question - how does the brain predict the future? And no, we will not talk about tarot cards, coffee grounds, astrology and other unscientific things. We will talk about how a person’s brain, using existing knowledge, building up logical chains and analyzing a situation, is able to foresee the near future. Researchers paid attention to this aspect not out of idle curiosity, but in order to better understand the processes in the human brain during the development of certain diseases, including Parkinson's disease. What exactly did scientists know, how did they conduct the experiments, and what can this mean for medicine in the future? The report will help us find answers to these questions. Go.
The basis of the study
Exaggeratedly speaking, the brain is the most important human organ. Of course, without a heart, the brain will not receive the oxygen it needs and die, so the heart is more important? Is not it? I agree, all organs are important, all organs are needed. However, our brain with you controls everything else: other organs, systems, processes. Your nose has itched - you know this thanks to receptors that transmit information to the brain. A trivial example, but you understand the essence. As a conclusion - to lose the power of your brain is one of the most terrible things that can happen to a person. And, unfortunately, there are many diseases that with one or another force "suppress" the normal functioning of the brain: dementia, Parkinson's disease, Alzheimer's disease, etc. Even mental disorders are directly related to the work of the brain, more precisely to the disorders that occur in this organ. Such a complex system
Today, scientists have decided to pay attention to such a vague concept as "predicting the future." It sounds like the name of a cheap production TV show, all that is missing is a crystal ball and the phrase “I see, I see ...”. But jokes are jokes, and our brain is capable of such, although not at such a paranormal level, as many would have liked.
The whole essence lies in small, sometimes invisible things, events and actions. As an example, scientists cite a basketball player who, due to experience, throws the ball in this way, being sure that the ball will fall into the net. Yes, it’s more like knowledge or causation, but the word “prediction” comes up as a short, simple and rather vivid term. Also, those of you who use cars might have noticed that many drivers start moving from their seats literally a split second before the traffic light turns green. None of this is nonsense like paranormal activity, and Scully and Mulder should not be called. All these are the results of our brain's complex processes. Even when you and your friend throw a ball at each other, why do you catch it? You see his trajectory, because you know how your friend most often makes a throw. Our brain collects such information and stores it for further use in order to simplify certain tasks. Why analyze something that already happened exactly the same? You can respond to the process by a known pattern and get the desired result. In our children's example - catch the ball.
We do not notice all these thought processes, we do not think about them (no matter how punse it sounds). But the disruption of these processes greatly affects the lives of people who suffer from various diseases of the brain and nervous system.
In order to understand how to make life easier for such people, it is first necessary to clearly understand the principle of operation of this prediction mechanism that our brain uses. Is it context sensitive or is it just as such.
First of all, scientists note that temporal predictions may be related to the quasi-periodicity of a number of stimuli (speech, music, biological movements). That is, endogenous changes are matched with external periodic signals. On the other hand, temporal forecasts can also be formed if there is only an aperiodic series of events. They can also be formed in complete isolation when we already know the gap between two events. The latter is well described by the example of the drivers I mentioned earlier. The driver often drives on a road where there is a traffic light. He knows how this traffic light works. And the driver no longer needs to even look at it in order to start at the moment the green light comes on. This is the isolated formation of the forecast in view of the previously obtained knowledge regarding this particular situation. In this case, the driver’s brain not only knows that under normal conditions the green light comes on, but also knows when it will happen. Call it an internal stopwatch. Thus, this prediction is temporary, that is, the brain foresees an event after a certain time.
Neuroscientists are still arguing about the nature and mechanism of temporal forecasts. In today's study, scientists believe that they have found where the answer lies with the question of the origin of temporal forecasts - the brain. But this is understandable. More specifically in the cerebellum and basal ganglia.
Here we can see the location of the cerebellum.
The first "brain piece" - the cerebellum - the department responsible for the coordination of our movements and balance. It is directly connected to the cerebral cortex, the spinal cord, the extrapyramidal system, the brain stem, and who you think with, of course, the basal ganglia. This whole team gives the cerebellum information, which allows the emu to make adjustments to movements, conscious or unconscious.
Recent studies have shown that the cerebellum plays an integral role in the formation of temporal forecasts. Namely, in determining the duration of intervals and determining the difference between two separate (individual) time intervals. In other words, it is the cerebellum that allows you to “feel” that 5-10 minutes have passed or 10-15 minutes, sorry for a primitive example.
In turn, the basal nuclei are already responsible for rhythmic judgments, that is, constant periodic phenomena (events).
It is also worth noting that the cerebellum is not controlled by human consciousness, while the basal nuclei, by contrast, are controlled by some theories. This theory is confirmed by the fact that the basal nuclei “fall asleep” during human sleep.
The basal nuclei are also involved in the regulation of motor processes (as well as the cerebellum). In addition, they are activated during the time when you concentrate your attention. At this point, the basal nuclei secrete a substance called “acetylcholine,” which plays an important role in memory formation.
Such a small excursion into neurobiology has already helped us understand why the researchers identified exactly 2 brain regions — the cerebellum and the basal nuclei — as the main details of the temporal prediction mechanism.
Naturally, scientists must prove their theory. To do this, they used the so-called neuropsychological approach. And now more about the experiments themselves.
Preparing for the experiments
In the experiments took part as healthy subjects (as a control group) - 23 people, and people with cerebellar degeneration (CD) - 13 people and with Parkinson's disease (PD) - 12 people. An important aspect was that all the subjects were not musically active the last 5 years before the experiment, that is, they did not play musical instruments and did not sing in the choir. This small personal characteristic actually has tremendous significance in the study, in view of the fact that the subject's brain was not, so to speak, trained for such activities.
The CD group consisted of 7 women and 6 men, the average age was 51.6 years. The main diagnosis among the subjects of this group was spinocerebellar ataxia: 6 people - due to genetic overtones, 5 subjects - unknown / idiopathic etiology.
* 2 test participants were excluded because of their inability to complete the test task. Therefore, the actual number of participants in the CD group was 11, not 13.
The PD group consisted of 7 women and 5 men, the average age was 68.4. Before conducting the experiments, the participants in this group were tested with UPDRS (Unified Parkinson's Disease Rating Scale). The average value in terms of motor skills was 14.2.
Both groups were also tested for the presence / absence of other neurological diseases.
Due to the fact that there is a significant age difference between the CD and PD groups, the control group (healthy subjects) was also selected in accordance with this parameter.
The stimuli were colored squares displayed for 100 ms. In each experimental run, there were 2 or 3 red squares, followed by 1 white square, acting as a “signal” one. After it there was 1 green square - “target”, which was the main one in the test. The interval between the white and green squares was 600 ms or 900 ms.
The main task of the subjects was to press a key on the keyboard as soon as they see a target (green) square in front of them.
In the experiment there were 3 variants of similar experience, they are presented schematically in the image below.
A schematic representation of the three variants of experiments: rhythmic, single-interval and random.
In the first variant, there were 3 red squares, the interval between which was identical to what was between the signal and target squares. That is, 600 or 900 ms between each square, regardless of color and purpose. Thus this version of the test is the most predictable.
In the second version there were 2 red squares. Here the intervals have been changed. As we can see from the graph above, the interval between the red squares and between white and green is the same, but the interval between the last red and white is very different.
Thus, it becomes much more difficult to predict the appearance of a white square, but this does not have a significant effect on the test result, since the interval between the signal and target squares remains the same as between the first two (red).
In the third version of the test there were 3 red squares, the intervals between which were completely random in the range of 600 ... 900 ms. Thus, the rhythm of the appearance of all squares is greatly disturbed, respectively, it is very difficult to predict the appearance of the next, to say the least. To predict the appearance of the target square becomes impossible.
In addition, 25% of the tests carried out did not have a target square (green) at the end of the sequence in order to avoid premature responses and, accordingly, make the results more accurate.
The process of experimental testing of the subjects was carried out in a closed room with dimmed lighting and without sound stimuli. Tests were presented on a normal monitor on a gray background. The distance between the monitor and the subject was 50 cm.
In the course of the experiment, the subjects made 3 runs (1 for each of the options described above) of 32 tests (16 at intervals of 600 ms and 16 - at 900 ms). 25% of all tests in a random order were "tricks", that is, did not contain the target green square.
An error message was displayed on the monitor if the participant responded (pressed a key) until the target square appeared on the monitor or during the “test-trick” (when there is no target square at all), as well as when the response delay is 3 seconds.
Now that we know who participated in the tests and how they were conducted, we should familiarize ourselves with the results.
As it is not difficult to guess, the reaction time (RT) is the most basic indicators during the study of the results of the first two test variants (rhythmic and single interval). This indicator should be, logically, significantly higher in the test at random intervals.
RT variance analysis was conducted for all 4 groups of subjects. Why 4 groups, you ask? There are in mind the following groups:
- CD - 11 people;
- CD-matched (control group corresponding to the average age of the CD group) - 11 people;
- PD - 12 people;
- PD-matched (control group corresponding to the average age of the PD group) - 12 people.
The results of analysis of variance of experimental data.
In graph A, we see the results of counting RT for a group of CDs (people with cerebellar degeneration). The following peculiarity is visible here: the reaction rate of test participants with random intervals and a single interval test is very similar. While the RT rhythm test is significantly better. The control group (CD-matched) showed a different trend. The reaction rate at random intervals was, as expected, the greatest. But the other two tests showed about the same results.
Simply put, both the CD group and the corresponding control group both did an excellent job with test number 1 (rhythmic) and equally bad with test number 3 (random), which was also quite logical and expected. But here in test number 2 there are significant differences. People suffering from cerebellar degeneration could not cope with a single-interval test as successfully as the control group (people without a disease).
Comparison of the results of the other two groups: PD (with Parkinson's disease) and PD-matched (the same average age as the PD group, but without the disease) showed different results. So, surprising is the fact that the PD group coped with the test number 2 (single interval) is almost as good as the control group of subjects. At the same time test number 3 (random) showed, as expected, low results. Test No. 1 showed not only the difference between the PD group and the corresponding control group, but also the difference between the PD group and the CD group. That is, patients with Parkinson's disease show significantly worse results than patients with cerebellar degeneration.
The ratio of the results of the analysis of tests of all groups we can see in the graphs above.
More detailed information about the study and the calculation of test results can be found in the report of scientists and additional materials to it.
Thanks to this study, scientists were able to confirm the fact that the cerebellum and the basal nuclei play an extremely important role in understanding how the human brain is able to predict certain events based on experience, the nature of the frequency of occurrence of an event and its frequency. Analysis of data from control groups and subjects suffering from Parkinson's disease only confirmed the theory put forward several years ago.
Understanding the work of the brain, even such seemingly insignificant characteristics of the brain, can be helpful in the diagnosis of various neurological diseases. The prospect of using such experiments as a basis for the future is still very vague in the study of treatment methods. However, taking such insignificant but important steps, scientists approach the understanding of one of the most unexplored and most complex objects in the world - the human brain.
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