"Stereotactic Approaches to Monkey Brain" is a summary title for four projects that I have been involved in at the Primate Center in the past year. These projects have been described separately by the Principal Investigators. The following comments supplement these descriptions, emphasizing my own role in each one. 1. Limbic Seizures and Neurobehavioral Development (with Dr. Virginia Gunderson). This project, in which we are studying the effects of induced seizures in very young macaques, evolved in part from my collaboration in previous years with Dr. Karen Gale to examine seizures induced in adolescent and young adult monkeys. My principal role in these studies has been to arrange for the induction of seizures by focal drug injections at sensitive sites in the brain. In the past year we began using the curved-injector technique I developed several years ago to access an extended portion of the hippocampal area with an acute injection. Results have been very encouraging, in terms of seizure effects and histological effects. We have also experimented with treatment of the entorhinal cortex, again along an extended trajectory, both by curved injector and by the access fiber technique I have been developing. In addition, I have performed several acute and chronic electrode implantations in the hippocampus to supplement data from epidural electrodes in these monkeys. 2. Dopaminergic and GABAergic Actions of Pallidal Discharge (with Drs. Marjorie Anderson and John Buford). In this project we are examining the effects of dopamine receptor and GABA receptor antagonists in the putamen on neuronal activity in the globus pallidus. My role has been to implant an access fiber for repeated drug application throughout several millimeters of the putamen. I have begun to use a thinner PAN-PVC fiber for this purpose, measuring 0.6 mm in diameter instead of 1.0 mm. I have also begun making a tiny nylon monofilament coil for internal support of the fiber. In addition, I am now using a thin lining of UV-sensitive glue to prevent drug from passing into the brain through the walls of the leading and trailing portions of the fiber. These techniques replaced earlier, less reliable, methods. 3. Neural Substrate of Learning (with Drs. Douglas Bowden and Richard Martin). In this project, which involves electrical stimulation of the brain as a reward for learning a visuomotor task, I am responsible for platform implantations to enable the targeting of subcortical regions for electrical stimulation. Long-range plans include the implantation of an access fiber in prefrontal cortex to examine the effects of drug administration on learning. 4. Computerized Brain Atlas for Macaca fascicularis (with Drs. Bowden and Martin). I became involved in this project because I have developed software that enables me to make a far more detailed MRI model of a monkey's brain in preparation for access fiber implantation or acute stereotactic treatment with injectors or electrodes. The software permits microcomputer reformatting of a large series of MRI pictures to rotate them in three dimensions to any desired position, with minimal loss of information. Given this capability, I can reorient the images of the head and brain into the stereotactic frame of reference to be used in surgery , without using the cumbersome stereotactic device I have previously used for aligning the head within the MRI unit. The MRI coils can be placed directly on the monkey's head instead of several inches away, resulting in a much more detailed picture. From the point of view of the computerized brain atlas, the software enables reorienting of an experimental plane of section (tomographic or histological) to match the template brain of the atlas (or vice versa), for the purpose of archiving neuroanatomical data. I have also created another piece of software that translates the structures and labels of Dr. Bowden's Template Atlas into a consolidated format compatible with this reformatting software and with other operations for use on the internet.