Functional imaging of the monkey brain

Functional magnetic resonance imaging (fMRI) has become an essential tool f or studying human brain function. Here we describe the application of this technique to anesthetized monkeys. We present spatially resolved functional images of the monkey cortex based on blood oxygenation level dependent (BO LD) contrast. Checkerboard patterns or pictures of primates were used to st udy stimulus-induced activation of the visual cortex, in a 4.7-Tesla magnet ic field, using optimized multi-slice, gradient-recalled, echo-planar imagi ng (EPI) sequences to image the entire brain. Under our anesthesia protocol , visual stimulation yielded robust, reproducible, focal activation of the lateral geniculate nucleus (LGN), the primary visual area (V1) and a number of extrastriate visual areas, including areas in the superior temporal sul cus. Similar responses were obtained in alert, behaving monkeys performing a discrimination task.