Spaceflight, in addition to exploring the unknown universe, can also help us people on Earth to understand how gravity affects our brain’s visual perception.
Humans have evolved under the constant influence of gravity, although we don’t usually notice it. The human brain can identify a living creature based on its movements, but it is difficult to do this upside down. However, to what extent this phenomenon is shaped by the Earth’s gravitational field is still unexplored.
Researchers from the Chinese Academy of Sciences and the China Astronaut Research and Training Center conducted a spaceflight experiment with Chinese astronauts during the Shenzhou manned flight missions. They found that prolonged time spent in microgravity decreased people’s tendency to be highly sensitive to biological motion but less sensitive to its reverse counterpart.
In the experiment, six astronauts, including two women, were exposed to microgravity conditions for 13 or 15 days during and after spaceflight, according to the study published recently in the journal Nature Communications.
The study found that for inverted stimuli, response accuracy tends to increase during flight and remains at a relatively high level for up to half to a month after flight. However, with vertical stimuli, accuracy decreases slightly during spaceflight and returns to normal after flight.
The results suggest that Earth’s gravity plays a central role in maintaining the orientation-dependent agreement of the visual system at biological movement signals. The researchers also conducted an analog spaceflight experiment on the ground, requiring a group of healthy participants to perform similar tasks before, during, and after 45 days of bed rest at a six-degree incline. The results corroborated the conclusions of the space experiment.
They also administered the tasks in two ground-control experiments, with one group isolated in a simulated space capsule for 30 days and the other in a regular lab environment. It shows that environmental factors unrelated to gravity cannot lead to a reduction in the reversal effect, according to the study.
However, such changes in sensitivity are not registered for face perception, which means that even in microgravity, people recognize upright faces faster than inverted faces. It highlights the special role of gravity in regulating kinematic motion analysis.
The researchers suggested that throughout the evolutionary history of human beings, they learned to use gravity for the visual analysis of the movement of biological organisms and their own bodies. By escaping Earth’s gravity, people can recalibrate their brain connectivity to provide an adaptive mechanism that helps us better adapt to changed environments, the researchers said.
Source: This news was originally published by Cgtn