Objective: The effect of STN DBS on the spectral power of oscillatory activity in the classic frequency bands in the motor cortex (MCtx) and sensorimotor cortex (SMCtx) was assessed in free-moving 6-hydroxydopamine (6-OHDA) lesioned hemiparkinsonian (HP) rats and sham-lesioned controls.

Background: Altered oscillatory activity in cortical-basal ganglia thalamic circuitries, especially enhanced activity in the beta band, have been linked to motor symptoms in Parkinson`s disease (PD). The subthalamic nucleus (STN) is targeted for deep brain stimulation (DBS) in PD and chronic stimulation has been shown to reduce beta band activity.

Method: Thirteen male Sprague Dawley rats (250-350g) were either rendered HP by unilateral injection of 6-OHDA (n=6), or by injection of saline (sham-lesioned; n=7) in the right medial forebrain bundle. After three weeks of surgical recovery, a DBS electrode was implanted in the STN, and an electrocortigram (ECoG) recording array was placed under the dura above the MCtx and SMCtx areas of the right hemisphere. All surgeries were performed under chloral hydrate (360 mg/kg; i.p.) anesthesia.  Seven days after surgery free-moving rats were individually recorded in three conditions: (1) basal activity, (2) during STN DBS, and (3) after STN DBS. Spectral power of oscillatory activity of theta (4-8 Hz), alpha (8-12 Hz), beta (12-30 Hz) and gamma (30-100 Hz), and average number of bursts in the oscillatory activity were analyzed in the MCtx and SMCtx areas and compared between HP and sham-lesioned rats.

Results: In HP rats, the relative power of theta band activity was lower, and beta and gamma activity was higher in MCtx and SMCtx, which was reverted towards control level by STN DBS both during and after stimulation (p < 0.001). Further analysis showed a higher count of bursts in beta and gamma oscillatory activity in HP rats in the MCtx and SMCtx, which was suppressed by STN DBS. No differences were found between MCtx and SMCtx.

Conclusion: Our results provide evidence that loss of nigrostriatal dopamine leads to increased beta and gamma oscillatory activity in motor and sensorimotor cortical areas, which is compensated by STN stimulation.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/impact-of-subthalamic-deep-brain-stimulation-on-sensorimotor-and-motor-cortical-oscillatory-activity-in-free-moving-hemiparkinsonian-rats/