Functional MRI (fMRI) has become an important tool for probing network-level effects of deep brain stimulation (DBS). Previous DBS-fMRI studies have shown that electrical stimulation of the ventrolateral (VL) thalamus can modulate sensorimotor cortices in a frequency and amplitude dependent manner. Here, we investigated, using a swine animal model, how the direction and orientation of the electric field, induced by VL-thalamus DBS, affects activity in the sensorimotor cortex. Adult swine underwent implantation of a novel 16-electrode (4 rows x 4 columns) directional DBS lead in the VL thalamus. A within-subject design was used to compare fMRI responses for (1) directional stimulation consisting of monopolar stimulation in four radial directions around the DBS lead, and (2) orientation-selective stimulation where an electric field dipole was rotated 0°-360° around a quadrangle of electrodes. Functional responses were quantified in the premotor, primary motor, and somatosensory cortices. High frequency electrical stimulation through leads implanted in the VL thalamus induced directional tuning in cortical response patterns to varying degrees depending on DBS lead position. Orientation-selective stimulation showed maximal functional response when the electric field was oriented approximately parallel to the DBS lead, which is consistent with known axonal orientations of the cortico-thalamocortical pathway. These results demonstrate that directional and orientation-selective stimulation paradigms in the VL thalamus can tune network-level modulation patterns in the sensorimotor cortex, which may have translational utility in improving functional outcomes of DBS therapy.
Bibliographical noteFunding Information:
This work was supported by the National Institutes of Health ( R01-NS081118 , R01-NS094206 , P50-NS098573 , U01-NS103569 ), NSF-GRFP (00039202, JPS), and the EU H2020 Marie Skłodowska RISE project (#691110, MICROBRADAM). We thank the Center for Magnetic Resonance Research (NIH core grants: P41-EB015894, P30-NS076408, U54-MH091657) and University of Minnesota Foundation for help with the MRI imaging used in this study (Dee Koski, Erik Solheid). We thank Heraeus Medical Components for the DBS lead (Robert Cass, Mark Hjelle, Mitch Lark, Paul Noffke, David Ohmann), NRTL lab members (Lauren Madden, Annie Brinda, Mojgan Goftari), and the Mayo Clinic Neuroengineering Group for guidance and fabrication of the stereotactic frame and targeting software (Dr. Kendall Lee, Steven Goerss, Dr. Joshua Jacobs).
- Directional DBS
- Functional magnetic resonance imaging
- High frequency stimulation
- Motor cortex
- Orientation selective DBS
- Somatosensory cortex