It can sometimes feel like time stands still – be it in the doctor’s waiting room, during a menial task, or whenever a train is delayed. On other occasions, time passes by in a flash – during a summer holiday, while jogging through a forest, or having a fascinating conversation with a friend. Depending on the situation, people experience the passing of time differently. We have sensory organs for various senses such as hearing, feeling, or taste, but we do not have any for our sense of time. This means that something must be happening in our brains – but we’re still unsure as to what exactly.
For people suffering from depression, time passes more slowly and sluggishly for them.
Do we have an internal clock?
Neuroscientist and psychiatrist Prof. Kai Vogeley and his colleague Dr. Mathis Jording have now found the first indication of a neural pattern for the perception of time. The Jülich researchers have been investigating how humans perceive time for years now. Do we have an internal sense of time and if so, how does it work? Is there some kind of time register for the mental clocks in our heads? And can our own experience of time be controlled or altered, for example, to improve our personal well-being?
Developing a time lab
Vogeley and Jording are interested in these questions from a basic research perspective. They also want to understand disturbances in the perception of time in the case of mental illnesses in order to develop new therapies. People suffering from depression, for instance, have an altered and often negative perception of time (see infobox). “They feel disconnected from the outside world because time passes more slowly and sluggishly for them. On occasion, time even seems to stand still, and in extreme cases it can feel like they are dead,” reports Vogeley from his psychiatric practice.
But where does our sense of time come from? Our skin allows us to feel if something is hot or cold, while our noses can help us perceive smells as flowery or musty. “These are direct senses. I don’t have to think about whether I’ve burned my finger. But when we experience time, we speculate afterwards and reconstruct from experiences how long something lasted, for example, by considering how often I looked at the clock while waiting,” explains Jording. These are conscious cognitive processes. But Jording wants to know what happens in the situation directly while time is passing. Are certain neural processes taking place in the head? Is there any experience of time at all during the situation, a subjective feeling for time?
To answer these questions, scientists developed an innovative concept in the EU research project VIRTUALTIMES, which is coordinated by Jülich. At its core is a new “time lab” in which the perception of time can be studied detached – as far as possible – from external influences or distractions. These studies are enabled by highly realistic, AI-based virtual reality technology.
When you enter the time lab, you see plain tables, dull walls, and an ordinary office chair. But as soon as you put on the VR headset, you find yourself in a virtual engine room made of steel in the middle of a spaceship. You can see through a window into space directly in front of you. Countless stars fly towards the test subjects. Their task is to report how fast or slow time seemed to them every 20 seconds. The researchers vary the number of stars and the speed at which they fly. “We therefore use simple visual stimuli to influence the experience of time in short intervals,” says Jording. At the same time, the researchers measure brain activity using an electroencephalogram (EEG). More than 200 people have taken part in various experiments in the starfield so far.
When we experience time, we later reconstruct how long something lasted from our experiences.
The researchers used some of the measurements to train a machine learning algorithm that was designed to detect a correlation between brain activity and the reported perception of time. The researchers then gave the AI the rest of the data and compared the AI’s prediction for the perception of time with the subjects’ statements. The AI was surprisingly accurate
AI detects a pattern
It seems that the algorithm had indeed detected a neural process, a pattern in the EEG measurements that enabled it to correctly predict the test subject’s perception of time. “For six months, we didn’t trust our own results,” says Jording. To increase the accuracy of the AI and to ensure that the predictions were not just a coincidence, the researchers conducted further studies – and their results were confirmed.
The researchers want to use the findings to develop a theory about the perception of time. They also want to investigate the role that the perception of time plays in human well-being and the connections between brain activity and the perception of time in mental illnesses. Ultimately, this might even lead to a therapy concept, a kind of time treatment. But it will take a long time before we get there, Vogeley suggests. However, he and Jording have established the basis for such a concept with their time lab and virtual starfield.
Perception of time in mental illness
People with depression often perceive time as slowing down. This can even go so far as a patient thinking they are dead because it feels like time is no longer passing for them. Some people with autism do not perceive time as flowing constantly, but rather in individual moments that string together like pearls. If this sequence is disrupted, for example if usual routines are interrupted, the perception of time also alters and the future then becomes less tangible. Some of those affected report that they no longer have a sense of time at all. Many people with schizophrenia can no longer reliably distinguish whether something is taking place in the past, present, or future. This can go so far that patients do not experience their present self as being the same person as in a previous moment.
This article is published in effzett 2/2024. Text: Katja Engel
