At the Massachusetts General Hospital, Boston, a group led by Anders M. Dale, PhD, is studying microscopic and system-level spatiotemporal imaging of the brain. Imaging of the living human brain at work has become possible, at the systems level, over the past decade, thanks to advances in the application of technologies such as positron-emission tomography and functional MRI. These tomographic methods, however, do not bridge the vitally important gap that still exists between their level of resolution and the circuit level of the neural models used in animal studies.
This work is intended to result in an integrated technology suite that will address the neglected area. Improving the spatiotemporal resolution of noninvasive imaging will lead to the ability to image the column-level and laminar-level neural units directly. This will provide the bridge between cellular and system levels of imaging.
The second goal of this research is to improve understanding of the relationship between imaging measurements (observed activity) and the biophysics of the neuronal activity through which the observable factors are generated. Two technologies are the primary subjects of this project. The first is MRI (including functional MRI) of extremely high resolution that employs phased-array coils, gradients of very high strength, and other advances. Field strengths of 3 T and 7 T are being used for imaging nonhuman primates, and rats are being imaged at 9.4 T. The second technology is tomographic optical imaging, for which physiolog-ical range and resolution are being extended through the employment of direct reflectance imaging, optical scanning microscopy, and diffuse optical tomography.
Invasive techniques will be used to determine the validity of these approaches in imaging the visual cortex of macaques and the whisker barrel cortex of rats. This work will then be extended to animal models of migraine and cerebrovascular accident. The design of the experiments that constitute this project will lead investigators in a series of steps from more invasive imaging to less invasive techniques. In addition, it will permit the researchers to begin working in areas where there is already a considerable amount of knowledge and move toward human studies, where use of spatiotemporal imaging tools will be pioneering work.