When preparing to interpret what we see, nerve cells maintain a state of balance, which may explain why a healthy brain can block out distractions, according to new research.
Autism and other developmental disorders impair that ability to focus attention, which is essential to our daily lives.
The new research, which appears in Nature Communications, marks a departure from the established view of how the brain tackles the task of identifying what is important.
Too much information
“The visual world contains more information than our brains can handle,” says coauthor Adam Snyder, an assistant professor in the brain and cognitive sciences department at the University of Rochester and UR Medicine Del Monte Institute for Neuroscience.
“This research shows that when anticipating stimulus, the brain maintains a pattern consisting of stimulated and unstimulated neurons and that these patterns differ from when the brain is actually processing information,” Snyder says.
While scientists know that the process of paying attention amplifies neural signals in the brain in order to prepare for relevant information, how the brain achieves this state of readiness remains unknown. One theory that has gained acceptance among the neuroscience community is that the nerve cells in the brain anticipate stimuli and maintain a heightened state of readiness.
“The prevailing view is that something happens to activate neurons so they will amplify the response to stimuli, like turning up the stereo so when the music starts it is already louder,” Snyder says. “Our suspicion is that the brain doesn’t work this way because the problem when you crank up the volume is you also get static noise.”
The inability to parse through stimuli and identify what is important characterizes disorders like autism. This often manifests in oversensitivity to certain visual or auditory environments where the brain has difficulty in separating the relevant information from “static.” Over time, this inability to focus and block out distractions can give rise to atypical social behavior.
Electrical stimulation therapy
In the new research, researchers monitored a large number of neurons simultaneously in the visual cortex—the part of the brain responsible for processing visual stimuli—in animals. They recorded neural activity as the animals performed tasks that required a response to visual cues.
They found that when anticipating stimuli, the neurons in the visual cortex essentially maintained a state of balance. For every neuron that was stimulated and at the threshold of firing, there were others that were in a resting state.
“This tension between alert and relaxing neurons is akin to when our muscles tense in anticipation,” says Snyder. “While some muscle fibers are contracting, others are extending, allowing us to quickly and strongly react and move.”
While the research focused on the visual cortex, the mechanisms appear to be consistent across the brain and could explain difficulties associated with the processing of other forms of stimuli, like sound and touch.
Understanding how the brain prepares to receive stimuli—and how dysfunction in this system leads to impairment—could open the door to new electrical stimulation therapies that could help teach the brain how to process information more effectively.
Additional coauthors are from Carnegie Mellon University and the University of Pittsburgh. The National Eye Institute, the National Science Foundation, Research to Prevent Blindness, the Eye and Ear Foundation of Pittsburgh, and the Simons Foundation supported the work.
Source: University of Rochester