“When you reach capacity there is a loss of feedback coupling,” said senior author Earl Miller, Picower Professor of Neuroscience at MIT’s Picower Institute for Learning and Memory. That loss of synchrony means the regions can no longer communicate with each other to sustain working memory.
Maximum working memory capacity – for instance the total number of images a person can hold in working memory at the same time – varies by individual but averages about four, Miller said. Researchers have correlated working memory capacity with intelligence.
Understanding what causes working memory to have an intrinsic limit is therefore important because it could help explain the limited nature of conscious thought and optimal cognitive performance, Miller said.
And because certain psychiatric disorders can lower capacity, said Miller and lead author Dimitris Pinotsis, a research affiliate in Miller’s lab, the findings could also explain more about how such disorders interfere with thinking.
“Studies show that peak load is lower in schizophrenics and other patients with neurological or psychiatric diseases and disorders compared to healthy people,” Pinotsis said. “Thus, understanding brain signals at peak load can also help us understand the origins of cognitive impairments.”
The study’s other author is Timothy Buschman, assistant professor at the Princeton University Neuroscience Institute and a former member of the Miller lab.