Source Activity, Connectivity, and Causality in Tinnitus Patient Modulated by Electrical Cortical Stimulation.
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1
Medical College of Wisconsin, United States
ECS of the auditory cortices (ACs) has been shown to reduce the severity of tinnitus [1]. Determining why some patients respond better than others may help us develop better neuromodulation strategies. Here, we use Magnetoencephalography (MEG) to estimate spontaneous brain activity, connectivity, and causality during and off CS of our best responder patient suffering from right unilateral tinnitus with an implanted CS device (Northstar Neuroscience) stimulating the left secondary AC at 40Hz (0.15ms pulse width). The SSS and SSP algorithms were used for denoising. At the sensor level, CS decreased theta power, increased gamma and beta power, and increased the power correlation across gamma, and between alpha and beta. At the source level, CS increased gamma and beta power in a large-scale temporo-frontal network (AC, DLPFC, VMPFC, frontal pole, orbitofrontal, anterior temporal lobe, insula, and thalamus); decreased theta power in insula, thalamus, and MFG; and suppressed the mu rhythm [2]. Resting state source connectivity (correlation (COR) and coherence (COH)) and causality (partial directed coherence (PDC), and direct causality) revealed that the CS electrodes and their nearest AC regions were correlated, coherent, and had causal influence over regions in the temporal lobe, including BA 41, 42, 22, 21, 37, and thalamus [3]. The COH and PDC also included BA 9, 10, 46, 40, PCC, IFG, and VMPFC. CS had a 40Hz-specific disruption of resting state network communication as measured by the PDC. Overall, there was less gamma PDC; more delta PDC; less theta PDC in ACC, motor cortex, and SMA; and a differential pattern of beta PDC in BA 40, SMA, thalamus, fronto-temporal cortices. These results provide evidence in favor of the Thalamocortical Dysrhytmia (TCD) hypothesis of tinnitus, and suggest that CS may prove to be an effective treatment of tinnitus when targeted to brain regions exerting a causal influence over key brain regions causally linked to tinnitus.
References
1. Friedland DR, et al., Feasibility of Auditory Cortical Stimulation for the Treatment of Tinnitus, Otol. & Neurotol. 28(8), 1005-12, 2007.
2. Ramirez RR, et al., Neuromagnetic Source Imaging of Abnormal Spontaneous Activity in Tinnitus Patient Modulated by Electrical Cortical Stimulation. IEEE EMBS, Minneapolis, Sept. 2-6, 2009.
3. Ramirez RR, et al., Abnormal source activity and causal connectivity in tinnitus patient modulated by cortical stimulation. Society for Neuroscience, Chicago, 837.5, Oct. 17-21, 2009.
Conference:
Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010.
Presentation Type:
Poster Presentation
Topic:
MEG: Clinical applications
Citation:
Ramirez
R,
Kopell
B,
Butson
C,
Friedland
D,
Gaggl
W and
Baillet
S
(2010). Source Activity, Connectivity, and Causality in Tinnitus Patient Modulated by Electrical Cortical Stimulation..
Front. Neurosci.
Conference Abstract:
Biomag 2010 - 17th International Conference on Biomagnetism .
doi: 10.3389/conf.fnins.2010.06.00301
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Received:
05 Apr 2010;
Published Online:
05 Apr 2010.
*
Correspondence:
Rey Ramirez, Medical College of Wisconsin, Milwaukee, United States, rrramirez@mcw.edu