neuroanatomy
Tapping Into The Brain’s Primary Motor Cortex
Posted on by Dr. Francis Collins
If you’re like me, you might catch yourself during the day in front of a computer screen mindlessly tapping your fingers. (I always check first to be sure my mute button is on!) But all that tapping isn’t as mindless as you might think.
While a research participant performs a simple motor task, tapping her fingers together, this video shows blood flow within the folds of her brain’s primary motor cortex (gray and white), which controls voluntary movement. Areas of high brain activity (yellow and red) emerge in the omega-shaped “hand-knob” region, the part of the brain controlling hand movement (right of center) and then further back within the primary somatic cortex (which borders the motor cortex toward the back of the head).
About 38 seconds in, the right half of the video screen illustrates that the finger tapping activates both superficial and deep layers of the primary motor cortex. In contrast, the sensation of a hand being brushed (a sensory task) mostly activates superficial layers, where the primary sensory cortex is located. This fits with what we know about the superficial and deep layers of the hand-knob region, since they are responsible for receiving sensory input and generating motor output to control finger movements, respectively [1].
The video showcases a new technology called zoomed 7T perfusion functional MRI (fMRI). It was an entry in the recent Show Us Your BRAINs! Photo and Video Contest, supported by NIH’s Brain Research Through Advancing Innovative Neurotechnologies® (BRAIN) Initiative.
The technology is under development by an NIH-funded team led by Danny J.J. Wang, University of Southern California Mark and Mary Stevens Neuroimaging and Informatics Institute, Los Angeles. Zoomed 7T perfusion fMRI was developed by Xingfeng Shao and brought to life by the group’s medical animator Jim Stanis.
Measuring brain activity using fMRI to track perfusion is not new. The brain needs a lot of oxygen, carried to it by arteries running throughout the head, to carry out its many complex functions. Given the importance of oxygen to the brain, you can think of perfusion levels, measured by fMRI, as a stand-in measure for neural activity.
There are two things that are new about zoomed 7T perfusion fMRI. For one, it uses the first ultrahigh magnetic field imaging scanner approved by the Food and Drug Administration. The technology also has high sensitivity for detecting blood flow changes in tiny arteries and capillaries throughout the many layers of the cortex [2].
Compared to previous MRI methods with weaker magnets, the new technique can measure blood flow on a fine-grained scale, enabling scientists to remove unwanted signals (“noise”) such as those from surface-level arteries and veins. Getting an accurate read-out of activity from region to region across cortical layers can help scientists understand human brain function in greater detail in health and disease.
Having shown that the technology works as expected during relatively mundane hand movements, Wang and his team are now developing the approach for fine-grained 3D mapping of brain activity throughout the many layers of the brain. This type of analysis, known as mesoscale mapping, is key to understanding dynamic activities of neural circuits that connect brain cells across cortical layers and among brain regions.
Decoding circuits, and ultimately rewiring them, is a major goal of NIH’s BRAIN Initiative. Zoomed 7T perfusion fMRI gives us a window into 4D biology, which is the ability to watch 3D objects over time scales in which life happens, whether it’s playing an elaborate drum roll or just tapping your fingers.
References:
[1] Neuroanatomical localization of the ‘precentral knob’ with computed tomography imaging. Park MC, Goldman MA, Park MJ, Friehs GM. Stereotact Funct Neurosurg. 2007;85(4):158-61.
[2]. Laminar perfusion imaging with zoomed arterial spin labeling at 7 Tesla. Shao X, Guo F, Shou Q, Wang K, Jann K, Yan L, Toga AW, Zhang P, Wang D.J.J bioRxiv 2021.04.13.439689.
Links:
Brain Basics: Know Your Brain (National Institute of Neurological Disorders and Stroke)
Laboratory of Functional MRI Technology (University of Southern California Mark and Mary Stevens Neuroimaging and Informatics Institute)
The Brain Research Through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)
Show Us Your BRAINs! Photo and Video Contest (BRAIN Initiative)
NIH Support: National Institute of Neurological Disorders and Stroke; National Institute of Biomedical Imaging and Bioengineering; Office of the Director
The Amazing Brain: Mapping Brain Circuits in Vivid Color
Posted on by Dr. Francis Collins
Hop aboard as we fly up, down, left, and right through the information highways of the human brain! This captivating and eye-catching video was one of the winners of the 2019 “Show us Your Brain!” contest sponsored by the NIH-led Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative.
The video travels through several portions of the brain’s white matter—bundles of fiber that carry nerve signals between the brain and the body, as well as within the brain itself. Fiber colors indicate directionality: left-right fibers (red), front-back fibers (green), and top-bottom fibers (blue).
Looking from the back, we start our journey deep within the brain in the limbic system, the area that helps control emotion, learning, and memory. About three seconds in, visual fibers pop into view extending from the eyes to various brain areas into the occipital lobe (one of four major brain lobes) in the back of the brain.
About two seconds later, flying over top as the brain starts rotating, we see various fiber bundles spray upward throughout the cerebral cortex, communicating information related to language processing, short-term memory, and other functions. About halfway through the video, several green bundles emerge arching across the brain’s midline. These bundles, called the corpus callosum, house the fibers enabling communication between left and right sides of the brain. Finally, the video closes as we see many different fiber bundles lighting up all over, enabling communication between different cortical and subcortical portions of the brain through association and projection pathways.
Dynamic maps like these are created using a 3D imaging technique called diffusion MRI tractography [1]. The technique tracks subtle pathways of water movement in the brain, and allows researchers to model the physical properties (connectional anatomy) that underlie the brain’s electrical properties (neuronal signaling). Postdoctoral researcher Ryan Cabeen and Arthur Toga, director of the University of Southern California Mark and Mary Stevens Neuroimaging and Informatics Institute, Los Angeles, used the method to study how white matter changes in developing and aging brains, as well as in brains affected by neurodegenerative or neurological disorders.
Scientific animator Jim Stanis produced the video with Cabeen and Toga. The team first created a population-averaged brain using high-quality diffusion MRI datasets from the Human Connectome Project ,and then used sophisticated computational tools to delineate each bundle manually .
The tractography technique lets scientists visualize and quantitatively analyze the brain’s wiring patterns, complementing our understanding of how the brain functions. Such methods are especially useful to learn about the organization of deep-brain areas that remain out of reach for scientists using current tools and imaging techniques.
Reference:
[1] Kernel regression estimation of fiber orientation mixtures in diffusion MRI. Cabeen RP, Bastin ME, Laidlaw DH. Neuroimage. 2016 Feb 15;127:158-172.
Links:
Arthur Toga (USC Mark and Mary Stevens Neuroimaging and Informatics Institute, Los Angeles)
Ryan Cabeen (USC Mark and Mary Stevens Neuroimaging and Informatics Institute)
qitwiki—Information about the Quantitative Imaging Toolkit (USC)
Human Connectome Project (USC)
Show Us Your Brain Contest! (BRAIN Initiative/NIH)
Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)
NIH Support: National Institute of Neurological Disorders and Stroke; National Institute of Mental Health
