Evidence for heading signals independent of head direction in humans

Generally, when humans walk or move in space, their heads are thought to be facing in the direction of travel. Nevertheless, movement direction and head orientation are distinct components involved in processing different types of spatial information.

Researchers at the University of California, Irvine and Boston University recently unveiled signals related to heading expressed in the human mind that appear to be independent of head direction. Their paper is Journal of Experimental Psychology: Generalcould soon open new avenues for neuroscience and psychological research focused on spatial navigation.

“We were interested in finding the first building blocks of navigation,” Liz Krastill, senior author of the paper, told Medical Xpress.

“Finding your way can be complicated, but in a sense, to track your location, you need some basic information such as your speed, how long you've been going, and in what direction you're going. We also took inspiration from research in animals, which found certain types of cells that track things like time, distance, and head direction, so we know these types of basic information. I also wanted to find out.”

It turns out that head direction and heading provide very different information. Overall, direction plays a larger role than head direction in shaping the trajectory that humans and animals follow as they move through their environment.

Additionally, research has found that people's heads are not always facing the direction of travel. As part of the study, Chrastil and his colleagues conducted behavioral experiments aimed at looking for heading signals that are completely separate from head direction.

“One of our collaborators on this project works in the visual field, so we took inspiration from vision science, and we wanted to see if we could use some of those methods. ,” Christil explained.

“We used a method called adaptation. You may have seen adaptation when you stare at something green for a long time and then look at a white wall and it appears red. You may also have seen adaptation when you stare at something green for a long time and then look at a white wall. There is also the motor adaptation effect (also known as the motor after effect), where when you see something moving down and it is not moving, it appears to be moving up.

In the context of this study, adaptation is essentially a change in perception that accompanies continued stimulation in a particular direction. In behavioral experiments, Christil and his collaborators attempted to generate movement aftereffects related to participants' perceived direction of movement.

“Participants observed movement in a long hallway,” Christil said. “It had two ends, one end was the sun and the other end was the moon. The movement continued in one direction, for example towards the sun, but sometimes to separate the direction of travel from the direction of the head. , the direction it was facing was reversed, so it now appears to be heading in the opposite direction (i.e., it's still heading towards the Sun, but now it's heading towards the Moon).

Throughout the team's experimental trials, the apparent direction the participants were facing reversed several times while they continued to move toward the sun. Christil likens the effect created to the Teacup Ride at Disneyland. At Disneyland, things constantly rotate even if you're moving in the same direction.

“We then performed a short test in which the movement moved back and forth between the sun and the moon,” she explained. “At the end of the 10 seconds, participants say whether they think they moved more toward the sun or more toward the moon on that test. The key conditions are: toward the sun and toward the moon. He's in a 50/50 situation when he goes the same amount.'' ”

Essentially, the researchers determined that there was an adaptation if participants said they moved in a certain direction more than 50% of the time during a short test run. In other words, this means that their perception changed during the experiment because they were constantly moving towards the sun. Remarkably, this is exactly what the team observed.

“In the 50/50 condition and in the other conditions, participants changed their responses in the direction that suited them, indicating that there was some direction-sensitive signal,” Krastil said.

This recent study suggests for the first time the existence of a human heading signal that is independent of head direction. The collected findings raise interesting new questions about the unique contribution of heading to spatial navigation.

“Most previous studies in humans and animals have focused on head direction, so we hope our study will encourage other teams to test movement direction as a key factor.” added Christil. “We're also looking for similar signals in the brain, and using fMRI, we've found signs of directionality in the brain. This paper is still under review, but we hope it will be published soon. Masu.”