Noninvasive imaging technique tracks brain activity with pinpoint precision
Conventional functional magnetic resonance imaging (fMRI), a method of measuring brain activity, relies on the detection of oxygen levels in blood flowing throughout the brain. Unfortunately, this blood-oxygenation-level dependent (BOLD) technique has failed to provide clear measurements of the direction in which neuronal activity travels between different parts of the brain.
Seeking an imaging technique sensitive enough to show the direction of neuronal activity across different layers of the brain’s outermost region, called the cortex, an international collaboration led by IRP researcher Peter Bandettini, Ph.D., turned to laminar (layer-specific) cerebral blood volume (CBV) fMRI as a more specific and reliable alternative to more widely used BOLD-based fMRI. Analyzing data from healthy volunteers performing four different hand motor tasks such as pinching or tapping, the team was able to discriminate a different pattern of laminar activity in the primary motor cortex for each task. By comparing results with laminar fMRI scans taken when subjects were in a resting state, the researchers could further discern whether neuronal signals were traveling to or from the motor cortex and the brain’s sensory and other movement-related areas.
The study demonstrated the accuracy and usefulness of laminar CBV fMRI for tracking brain activity across cortical layers, determine its direction, and measure cerebral blood volume with sub-millimeter resolution. These findings open the door for more rigorous investigations of information flow between and within different regions of the brain.
Huber L, Handwerker DA, Jangraw DC, Chen G, Hall A, Stuber C, Gonzalez-Castillo J, Ivanov D, Marrett S, Guidi M, Goense J, Poser BA, Bandettini PA. (2017). High-resolution CBV-fMRI Allows Mapping of Laminar Activity and Connectivity of Cortical Input and Output in Human M1. Neuron. Dec 20;6(6):1253-1263.