a brain, one of the best tools neuroscientists have is the fMRI scan, which helps map blood flow, and therefore the spikes in oxygen that occur whenever a particular brain region is being used. It reveals a noisy world. Blood oxygen levels vary from moment to moment, but those spikes never totally flatten out. “Your brain, even resting, is not going to be completely silent,” says Poortata Lalwani, a PhD student in cognitive neuroscience at the University of Michigan.
Many fMRI studies filter out that noise to find the particular spikes researchers want to scrutinize. But for Lalwani, that noise is the most telling signal of all. To her, it’s a signal of cognitive flexibility. Young, healthy brains tend to have signals with a lot of variability in blood oxygen levels from moment to moment. Older ones vary less, at least in certain regions of the brain.
About a decade ago, scientists first showed the link between low neural signal variability and the kind of cognitive decline that accompanies healthy aging, rather than specific . A brain’s noisiness is a solid proxy for details that are more abstract, Lalwani says: “How efficient information transfer is, how well-connected the neural networks are, in general how well-functioning the underlying neural network is.”that change happens with age has been a mystery. So has the question of whether it’s reversible., Lalwani's team showed that a small dose of Lorazepam, an anti-anxiety medicine, could reverse the dip in signal variability, at least momentarily.
“Ten or so years ago, most people thought that variability in the brain was a bad thing,” says Cheryl Grady, a cognitive neuroscientist at the Rotman Research Institute who has studied brain signal variability but was not involved in Lalwani’s study. But now, she feels, more people realize the potential of this new metric. “I'm very much in favor of this whole approach.”began to suspect that the so-called noise in fMRI signals had a deeper meaning.
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