Studying task-related activity of individual neurons in the human brain

. By applying extracel-lular microelectrode recording techniques to the developing field of stereotactic neurosurgery, these investigators were able to precisely target and study the physiology of deep brain nuclei. Initial efforts were focused on mapping individual thalamic nuclei during abla-tive procedures (thalamotomy) for patients with Parkinson disease (PD). Subsequently, these techniques have been applied to target-ing a variety of other subcortical nuclei, including the subthalamic nucleus (STN) and pallidum, as well as the cingulate cortex and ventral striatum.Currently, microelectrode recordings have widespread use in stereotactic neurosurgery, for both ablative procedures and deep brain stimulation (DBS). They provide physiological information that helps to confirm and to refine the trajectory of the lesioning probe or DBS macroelectrode. Relying on anatomical targeting with stereotactic coordinates alone can lead to inaccurate positioning because of brain shift resulting from cerebrospinal fluid (CSF) loss, imaging distortion caused by magnetic field inhomogeneities and other sources of error