Introduction: Neurosurgical interventions that use active patient feedback, such as the implantation of a deep brain stimulating electrode, create an opportunity to conduct human behavioral experiments during the acquisition of invasive neurophysiology. Here, we present a modular, inexpensive system for auditory decision-making tasks, including stimulus presentation and collection of motor responses. Using our system, we characterize behavioral responses with latency to respond and accuracy of response. In addition, we analyze the temporal pattern of substantia nigra pars reticulata (SNr) spiking relative to specific task events.
Methods: We describe the implementation of an auditory-cued decision-making task designed for use in the intraoperative setting. We have created an auditory-stimulus guided, two-alternative forced choice (2AFC) task using the PsychToolBox suite developed in Matlab. Task responses are collected using an Arduino based single-hand held controller that has been customized with a 3D printed attachment. Neural activity is recorded from microelectrodes via an NeuroOmega system (Alpha Omega, Alpharetta GA). Task and neural data are aligned according to TTL signals sent from DATAPixx (VPixx Technologies, Montreal, Quebec), triggered by Matlab.
Results: We demonstrate the utility of a simple-to-implement sensory-motor task amenable to an intraoperative setting that can be combined with invasive neurophysiology. Data collected and analyzed to date demonstrates that single-unit activity reflects task variables associated with our 2AFC. Specifically, analysis of two putative SNr neurons show significantly (p<0.05, non-paired t-test) increased firing rate prior to movement execution, in comparison to firing rate following movement execution.
Conclusions: For very low cost and minimal effort, most clinical neural recording system can be adapted for concurrent intraoperative behavioral testing using our framework. Barriers to conducting intraoperative electrophysiological studies in awake behaving human subjects remain high, but our work should significantly decrease the effort needed to implement a system with rich recording capabilities.
Patient Care: By understanding how neural structures like the basal ganglia function in the parkinsonian state, we will be able to improve techniques like deep brain stimulation to maximize therapeutic efficacy.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Understand the unique opportunity provided by conducting intraoperative electrophysiological studies to elucidate cognitive processes. 2) Discuss, in small groups, how our single neuron findings fit with past work in animal models.