Nuclei deep in the brain, known as the basal ganglia, play a key role in motor actions. But their role in sensory integration and higher cognitive function is not well known. Intraoperative deep brain stimulation (DBS) provides the only window to measure the human electrophysiology of these subcortical nuclei. In the operating room, prior to the insertion of the stimulating electrode, recording microelectrodes are inserted into the target nuclei to provide electrophysiological confirmation that the right nucleus has been reached.
During this time, while the recording electrodes are still in place, sights and sounds can be presented to a patient while the responses of their neurons are recorded. The targets of the deep brain stimulation include the subthalamic nucleus (STN) and the globus pallidus internus (GPi) in Parkinson’s Disease and dystonia, and the ventral intermediate nucleus (Vim) in essential tremor.
We are working to find the fundamental properties of basal ganglia neurons. Unlike neuroimaging studies, which use the aggregation of thousands or even millions of neurons to collect data, we are recording from single cells. As a result, there is no guarantee that the cells we find will be involved in cognitive tasks. To tackle this challenge, we have developed an online analysis system, capable of stimulus presentation, spike detection, sorting, and hypothesis testing all within the operating room. This allows us to determine, on-the-fly, if the cells we're recording from respond to particular stimuli. If they do, we automatically perform more trials of that type. If the cells do not respond to any of the stimuli, we drive the recording electrodes to another depth and try again. This technique maximizes our chances of finding cognitively-involved neurons within these nuclei.
This work is being spearheaded by graduate student Ricky Savjani in my lab at BCM, in collaboration with neurosurgeon Dr. Albert Fenoy at UT Houston. Check back for updates.