A number of studies published over the past year have approached the question from different angles, all of which point in the same direction: Cognitive training may produce broader, measurable changes in the brain.

The field buzzed with excitement at the Alzheimer’s Association International Conference in July, where researchers presented new findings from the largest clinical trial investigating whether computerized brain-training exercises can reduce the risk of cognitive decline with age.

The trial, funded by more than $50 million from the National Institutes of Health, reflects growing interest in an intervention that is inexpensive, scalable and accessible to almost anyone with a computer or tablet.

Researchers have evaluated a wide array of measures, such as blood biomarkers, neuroimaging findings and assessments of memory, everyday functioning, quality of life and, ultimately, the onset of dementia.

Sandra Bond Chapman, a professor of behavioral and brain sciences and founder and chief director of the Center for BrainHealth at the University of Texas at Dallas, is helping lead an effort to create a more comprehensive metric. Her team’s BrainHealth Index combines measures of executive function, emotional well-being and social connectedness into a single score designed to track how an individual’s brain changes over time.

The surprise came when the blood tests were analyzed. Only the speed-training group showed favorable changes in Alzheimer’s-related biomarkers.

The finding led researchers to a part of the brain that rarely enters public conversation: the cholinergic system, a network of cells that supports attention, learning and memory. The system naturally declines with age — about 2.5 percent per decade — but deteriorates much more rapidly in Alzheimer’s disease.

“Our theory is that speed-processing exercises stimulate the cholinergic system in a way that influences biological pathways involving tau and amyloid,” Hye Won Chai, the study’s lead author and a research assistant professor at Clemson University, said.

The idea is consistent with findings from the McGill University study published in the peer-reviewed journal JMIR Serious Games that also showed training benefited the cholinergic system.

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The new science of brain workouts, beyond Sudoku and crosswords