The most highly evolved brain region in mammals is the prefrontal cortex, which regulates our thoughts, actions, and emotions through extensive connections with other brain regions. Studies in humans have shown that multiple parts of the prefrontal cortex are activated during memory tasks, but patients with damage to some of these areas do not always have memory problems. As a result, researchers have disputed whether memory deficits are caused by damage to individual brain areas subserving specific cognitive functions or by an interruption in the flow of information among widely distributed areas in the prefrontal cortex.
A recently proposed hypothesis reconciles these views by suggesting that cortical areas form a highly ordered network containing hubs that play a critical role in information processing, such that damage to a hub results in severe cognitive impairment. However, most investigations of network structure have relied on either anatomical studies or functional neuroimaging of spontaneous activity at rest, ignoring brain activity related to specific cognitive tasks.
In a study published this week in PLOS Biology, Yasushi Miyashita of the University of Tokyo School of Medicine and his colleagues used functional magnetic resonance imaging (fMRI) and a novel simulated-lesion method in monkeys to show that virtual damage to a prefrontal cortex hub, which was the most highly interconnected with other brain areas activated during a memory task, was predicted to produce the most severe memory impairment. By contrast, virtual damage to a highly interconnected prefrontal cortex hub that was previously identified in anatomical tracer studies was not predicted to produce severe memory problems. According to the authors, these findings lay the foundation for precisely predicting the behavioral and cognitive impact of injuries or surgical interventions in the human brain.