“We have lost the ability to question,” this phrase may not be just an expression of criticism of contemporary society. An experiment conducted on mice showed that the brain adapts over time to acute stimuli in its environment. As the organ matures, the areas responsible for processing sudden events become more tolerant.
A team of scientists from the University of Basel, Switzerland, studied the process of adaptation to unusual stimuli within the brain. The report was published in Advancement of science It shows how the responses of young mice are encoded compared to mature rodents.
The ability to identify unexpected events is essential to the survival of the species. By creating a conventional picture of the world, the brain can distinguish between rare and common stimuli. The process of identification in the field of neuroscience is known as Specific stimulus adaptation (Sasa). SSA has been frequently studied in adults, but is an unexplored area with young physiology.
To dig deeper into the mechanism, the Basel scientists focused their efforts on studying stimulus-specific adaptation in the brains of young mice. They attached electrodes to the rodents' bodies and subjected them to the Oddball test. In the experiment, also known as the “strange paradigm,” they were induced to hear repeated sounds with unusual interruptions. In parallel, computers recorded reactions at the sensory level.
The animals' reaction time and level decreased over the days, when subjected to the same test. By monitoring different parts of the brain, researchers realized that not all regions react with the same intensity. Some of them have become accustomed to the stimulation sooner. This phenomenon coincided with the natural growth of the organs. The mice lost their sense of surprise not out of habit, but because their sensory system was beginning to mature.
50-day-old mice and 20-day-old humans
According to the report, the animals' primary auditory cortex matures until day 50. Experiments began on day 20. The regions and times of their maturation are important. The “auditory startle pathway” begins in the periphery and ends in the cerebral cortex.
Extrapolating to human lifespans, 50 days in a rodent's life is equivalent to 20 human years. Therefore, the Basel exercise provides clues to explain why babies cry when they hear loud noises, and this fear disappears as they grow.
“Most of the reported knowledge about auditory development has been obtained from animals. However, it has high potential for application to humans, since the maturation of auditory skills in our species is very similar to that in mice.” The article concluded that the knowledge presented in this The work improves our understanding of how the response to startling sounds appropriately adapts to the environment in which the plastic brain matures, especially the still-vulnerable adolescent brain.