To eavesdrop brain, one of the best tools neuroscientists have is the fMRI scanner, which helps to map blood flow, and thus the spike in oxygen that occurs whenever a particular brain region is examined. use. It reveals a noisy world. Blood oxygen levels change from time to time, but those spikes never go away completely. “Your brain, even when it’s at rest, isn’t going to be completely silent,” says Poortata Lalwani, a doctoral student in cognitive neuroscience at the University of Michigan. She imagines the brain, even at its quietest, like a tennis player waiting to return: “He won’t stand still. He’ll pick up the pace a bit, ready for a backhand. “
Many fMRI studies filter out that noise to find specific spikes that researchers want to scrutinize. But for Lalwani, that noise is the most telling signal. For her, it’s a signal of cognitive flexibility. Young, healthy brains tend to signal with many changes in blood oxygen levels over time. Older people change less, at least in certain regions of the brain.
About a decade ago, scientists first linked low neural signal variability and the kind of cognitive decline that accompanies healthy, rather than specific, aging. Dementia. “Brain noise is a solid proxy for more abstract details,” says Lalwani: “How efficient is the transmission of information, how well connected is the neural network? , it’s generally how well the underlying neural network works”.
But why that change occurs with age has been a mystery. So there’s the question of whether it’s reversible.
In Result announced in november in Journal of NeuroscienceLalwani’s team has shown that a small dose of Lorazepam, an anti-anxiety drug, can reverse the decline in signal variability, at least momentarily. The drug modulates inhibitory messages in the brain but makes it more active, ready to react and respond quickly. In the study, the brain signals of older participants who had previously performed poorly on cognitive tasks returned to noise levels that looked similar to younger participants.
“Ten years ago, most people thought that brain signaling changes,” said Cheryl Grady, a cognitive neuroscientist at the Rotman Research Institute who has studied brain signal variability but was not involved in Lalwani’s study. Changes in the brain are a bad thing. But now, she feels, more people realize the potential of this new indicator. “I’m very supportive of this whole approach.”
Around 2008, researchers began to suspect that the so-called noise in the fMRI signal had deeper implications. In 2010, Douglas Garrett, then a PhD student, pointed out that change in blood oxygen fMRI signal predicts a person’s age better than the size of the mutations in those readings. His hunch is that standard deviation — a measure of how similar or different signals are in a raw data set — can tell stories by simply averaging spike sizes. is impossible.
