Neuroimaging May Be a Mind Reader

New Research Has Implications for the Diagnosis of Brain Disorders

Megan Brooks

May 27, 2011

May 27, 2011 — Whole-brain functional connectivity magnetic resonance imaging (MRI) appears to offer a previously unprecedented window into the mind, allowing scientists to tell whether a person is remembering the day's events, singing silently to themselves, performing mental arithmetic, or just relaxing, with a high degree of accuracy.

According to a new imaging study conducted by investigators at the Functional Imaging in Neuropsychiatric Disorders Laboratory, Stanford University, California, this ability to distinguish specific cognitive states in normal adults could prove valuable in the diagnosis brain disorders, including Alzheimer's disease.

"The ability to decode and distinguish specific cognitive states from brain imaging data constitutes a major goal of neuroscience," the researchers, led by Michael Greicius, MD, write.

Previous studies have focused largely on decoding brief events whose timing has been strictly controlled by the investigator, Dr. Greicius told Medscape Medical News.

"Essentially, everything that has been done in functional MRI to date has some kind of cognitive subtraction analysis built into it. There is always an investigator-imposed separation of 'on-task' and 'off-task,' with critically controlled timing for switching between events," he said.

The study was published online May 26 in Cerebral Cortex.

Snapshot of Brain Connectivity

Dr. Greicius and colleagues focused their efforts on decoding more natural, free-streaming, and purely subject-driven cognitive states, using functional connectivity MRI, which "provides kind of a snapshot of connectivity across the whole brain at once," Dr. Greicius said.

Dr. Michael Greicius

They obtained 4 separate imaging scans from 14 young men and women. During each scan, the volunteers performed 1 of 4 mental tasks — resting quietly, remembering the events of their day, subtracting numbers, or silently singing song lyrics. They did this at their own pace during uninterrupted scanning periods that ranged from 30 seconds to 10 minutes.

The scientists created maps of brain activity during each of the 4 tasks. They defined 90 functional regions of interest across 14 large intrinsic connectivity networks in the brain and looked at within-network and between-network connectivity.

A "classifier" trained to identify the specific patterns of whole brain connectivity for each mental activity correctly identified the 4 cognitive states with 84% accuracy, the scientists report. The classifier achieved the same level of accuracy when identifying these states in a second independent cohort of subjects.

Window Into Cognitive Processing

The brain at rest and the brain recalling the day's events. William R. Shirer, Greicius Lab, Stanford University School of Medicine.

These results, the scientists say, highlight the potential for whole brain functional connectivity analyses to provide "an experimental window into naturalistic, continuous subject-driven cognitive processing."

They say "face validity" for this approach comes from the finding that connectivity was significantly increased in a brain network connecting known memory regions like the retrosplenial cortex and the medial temporal lobe during the memory task.

The ability to use functional MRI to capture day-to-day cognitive states and map connectivity patterns of normal volunteers has implications for assessing individuals with cognitive disorders such as Alzheimer's disease, the scientists say.

They are already using this approach to develop diagnostic tests for Alzheimer's disease and other brain disorders in which network function within the brain is disrupted.

The study was funded by the Dana Foundation, the John Douglas French Alzheimer's Foundation, and the National Institutes of Health. The authors have disclosed no relevant financial relationships.

Cerebral Cortex. Published online May 26, 2011.

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