High-Resolution Mapping of Discrete Representational Areas in Rat Somatosensory Cortex Using Blood Volume-Dependent Functional MRI

The present study documents the use of an iron oxide-based blood-pool contrast agent in functional magnetic resonance imaging to monitor activity-related changes in cerebral blood volume (CBV) resulting from peripheral sensory stimulation and the application of this technique to generate high-resolution functional maps. Rats, anesthetized with α-chloralose, were imaged during electrical stimulation (3 ms, 3 Hz, 3 V) of forelimb or hindlimb. Activation maps were generated by cross-correlation of the measured signal response and a square-wave function representative of the stimulus for each image pixel. Multislice imaging produced functional maps consistent with the known functional anatomy of rat primary somatosensory (S-I) cortex. Imaging with improved temporal resolution demonstrated rapid (