Do you recall that odd feeling when — sitting on a train that you know is standing still — you suddenly feel that it is moving (!)? It happens when you are watching a moving train right beside you and there is no other reference point. There’s a name for that: vection, “the sensation of movement of the body in space produced purely by visual stimulation.”

It is a staple, of course, of IMAX films and virtual reality displays. And it’s a fairly easy illusion to produce:

It turns out that vection can be induced with any sufficiently decent screen and some scenery. Experimenters can put make people believe they’re spinning in a circle, zipping back and forth, and even turning nearly upside down. And they don’t have to try that hard. They don’t need to simulate the edges of a window, or a cockpit. All they have to do is make slight marks, right on the screen, that the person will adopt as their “point of view,” and then move the scenery around behind it. The brain does the rest.

Esther Inglis-Arkell , “What’s That Weird Feeling of Illusory Movement on Trains?” at Gizmodo (June 4, 2014)

Studying it can yield useful results as well:

Researchers recently discovered, from a study of macaque monkeys, that there is a type of neuron in the brain that is especially suited to tracking the motion of an object while one is moving oneself:

“While much has been learned previously about how the brain processes visual motion, most laboratory studies of neurons have ignored the complexities introduced by self-motion,” DeAngelis says. “Under natural conditions, identifying how objects move in the world is much more challenging for the brain.” …

The researchers discovered a type of neuron in the brain that has a particular combination of response properties, which makes the neuron well-suited to contribute to the task of distinguishing between self-motion and the motion of other objects.

“Although the brain probably uses multiple tricks to solve this problem, this new mechanism has the advantage that it can be performed in parallel at each local region of the visual field, and thus may be faster to implement than more global processes,” DeAngelis says.

University of Rochester, “How the brain interprets motion while in motion” at ScienceDaily (June 21, 2022) The paper is open access.

The neurons were found via fMRI (functional magnetic resonance imaging) in the middle temporal (MT) area of the macaques’ brains.

Of course, these neurons can be fooled but usually only for a short period.

Just for fun: Optical illusions: What causes them? Try some out! Illusions can be literal, physiological, or cognitive, depending on which aspect of your brain is the object of a con job on your vision. The brain’s optical center makes assumptions and takes shortcuts in order to cut down on the workload in a busy world. Sometimes these shortcuts are illusions.

You may also wish to read: A little-known structure tells our brains what matters now. Work with monkeys and mice has shed light on the filtering role of a neglected feature of the mammalian brain. The cuneate nucleus (CN) in the brain stem turns out to communicate regularly with your prefrontal cortex and spine as to what you had better notice.