| Abstract No.: | A-D1135 |
| Country: | Canada |
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| Title: | THE RELATIONSHIP BETWEEN LOCAL FIELD POTENTIAL AND NEURONAL DISCHARGE IN GLOBUS PALLIDUS OF PARKINSON’S DISEASE PATIENTS |
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| Authors/Affiliations: | 1 Moran Weinberger*; 1 William Hutchison ; 2 Mojgan Hodaie; 1 Jonathan Dostrovsky;
1 Dept. of Physiology, University of Toronto; 2 Division of Neurosurgery, Toronto Western Hospital, ON, Canada
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| Content: | Objective: Depth recordings in patients with Parkinson's disease (PD) have demonstrated prominent local field potential (LFP) oscillatory activity in the beta frequency (15-30 Hz) band in the subthalamic nucleus and the internal globus pallidus (GPi). Treatment with dopaminergic medications reduces these beta oscillations and results in oscillations at higher frequencies (around 70 Hz). In the GPi, beta activity is mainly evident in the local field potentials (LFPs) recorded from the macroelectrodes used for therapeutic high-frequency stimulation of this region. Although previous studies have revealed beta oscillatory neuronal activity in the GPi, the relationship between neuronal activity and LFPs in GPi remains to be elucidated. In this study, we examined the relationship of GPi neuronal firing with the simultaneously recorded LFP.
Methods: Neuronal firing and LFPs were simultaneously recorded from the GPi using two microelectrodes separated by about 600 um in two PD patients during functional neurosurgery.
Results: When patients were at rest and ‘off’ dopaminergic medications, beta oscillations were observed in the LFPs and these were coherent between the 2 electrodes. Of 72 cells recorded during the ‘off’ state, the firing activity of 19 (26%) was significantly correlated with the LFP recorded from one or both microelectrodes. However, significant oscillatory neuronal firing in the beta range was observed in only 4 cells. In patient A, the firing of 10 out of the 30 cells was correlated with the LFP and 5 of these cells were in the dorsal GPi and 5 in the ventral GPi. As expected, the average beta LFP power was not significantly different between the dorsal and ventral GPi in this patient. However, in patient B, the firing of 9 of the 42 cells was correlated with the LFP, and 8 of them were located in the ventral GPi whereas only one cell was found in the dorsal part. In this patient, the LFP beta power was significantly greater in the ventral part (p = 0.02). In patient A, recordings were also done following treatment with dopaminergic medications that induced dyskinesias. During this period spectral analysis of the LFP revealed peaks at around 9 and 70 Hz while beta activity was rarely observed. The firing of 2 of the 17 cells recorded was correlated with the LFPs at around 9 Hz. The firing rates of GPi cells in this patient were not significantly different between the ‘on’ and ‘off’ states (mean 74.8 vs. 71.3 Hz respectively).
Conclusion: These findings suggest that the oscillatory LFPs recorded from the GPi in PD patients off medication are associated with beta oscillatory synchronous activity in populations of GPi neurons and that dopamine suppresses this activity.
Supported by CIHR MOP 42505. |
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