July 13, 2013
Virtual Brain Capable Of Daydreaming Just As Humans Do
April Flowers for redOrbit.com - Your Universe Online
A team of international researchers, led by Washington University School of Medicine in St. Louis, has created a virtual model of the brain capable of daydreaming like humans do.
"We can give our model lesions like those we see in stroke or brain cancer, disabling groups of virtual cells to see how brain function is affected," said Maurizio Corbetta, MD, the Norman J. Stupp Professor of Neurology at Washington University School of Medicine in St. Louis. "We can also test ways to push the patterns of activity back to normal."
In the late 1990s to early 2000s, scientists recognized the brain stays busy even when not engaged in mental tasks. Prior research has identified several "resting state" brain networks, which are groups of different brain regions that have activity levels that rise and fall in sync when the brain is at rest. Disruptions in networks associated with brain injury and disease have been linked to cognitive problems in memory, attention, movement and speech.
The new model, described in the Journal of Neuroscience, was developed to help researchers learn how the brain's anatomical structure contributes to the creation and maintenance of resting state networks. The team started with a process for simulating small groups of neurons, including factors that decrease or increase the likelihood that a group of cells will send a signal.
"In a way, we treated small regions of the brain like cognitive units: not as individual cells but as groups of cells," said Gustavo Deco, PhD, professor and head of the Computational Neuroscience Group in Barcelona. "The activity of these cognitive units sends out excitatory signals to the other units through anatomical connections. This makes the connected units more or less likely to synchronize their signals."
Using data from brain scans, the team assembled 66 cognitive units in each hemisphere of the brain. Then they interconnected them in anatomical patterns similar to the connections present in the biological brain.
The model is constructed so that the individual units went through the signaling process at random low frequencies that had been observed in brain cells in culture and in recordings of resting brain activity.
The model was allowed to run while the researchers slowly changed the coupling, or the strength of the connections between units. At specific coupling values, the interconnections between the units sending impulses began to create coordinated patterns of activity.
"Even though we started the cognitive units with random low activity levels, the connections allowed the units to synchronize," Deco said. "The spatial pattern of synchronization that we eventually observed approximates very well--about 70 percent--to the patterns we see in scans of resting human brains."
Simulating 20 minutes of human brain activity required a cluster of powerful computers running the model for 26 hours. The researchers have been able to simplify the mathematics, however, so that the model will run on a typical computer.
"This simpler whole brain model allows us to test a number of different hypotheses on how the structural connections generate dynamics of brain function at rest and during tasks, and how brain damage affects brain dynamics and cognitive function," Corbetta said.