The ability to focus attention is a fundamental challenge that the brain must solve and one that is essential to navigating our daily lives. In developmental disorders such as Autism this ability is impaired. New research published in the journal Nature Communications shows that nerve cells maintain a state of balance when preparing to interpret what we see and this may explain why the healthy brain can block out distractions.
The new research, which was co-authored by Adam Snyder, Ph.D., an assistant professor in the University of Rochester Department of Brain and Cognitive Sciences and UR Medicine Del Monte Institute for Neuroscience, marks a departure from the established view of how the brain tackles the task of identifying what is important.
“The visual world contains more information than our brains can handle,” said Snyder. “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.”
While it is known 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,” said Snyder. “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.”
Disorders like Autism are characterized by the inability to parse through stimuli and identify what is important. This is often manifested 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.
In the new research, Snyder and his colleagues 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.
The researchers 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,” said 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 co-authors of the study include Byron Yu and Matthew Smith with Carnegie Mellon University and the University of Pittsburgh. The study was supported with funding from the National Eye Institute, the National Science Foundation, Research to Prevent Blindness, the Eye and Ear Foundation of Pittsburgh, and the Simons Foundation.