Pallidal Beta Activity Is Linked to Stimulation-Induced Slowness in Dystonia

BACKGROUND

Pallidal deep brain stimulation (DBS) effectively alleviates symptoms in dystonia patients, but may induce movement slowness as a side-effect. In Parkinson's disease, hypokinetic symptoms have been associated with increased beta oscillations (13-30 Hz). We hypothesize that this pattern is symptom-specific, thus accompanying DBS-induced slowness in dystonia.

METHODS

In 6 dystonia patients, pallidal rest recordings with a sensing-enabled DBS device were performed and tapping speed was assessed using marker-less pose estimation over 5 time points following cessation of DBS.

RESULTS

After cessation of pallidal stimulation, movement speed increased over time (P < 0.01). A linear mixed-effects model revealed that pallidal beta activity explained 77% of the variance in movement speed across patients (P = 0.01).

CONCLUSIONS

The association between beta oscillations and slowness across disease entities provides further evidence for symptom-specific oscillatory patterns in the motor circuit. Our findings might help DBS therapy improvements, as DBS-devices able to adapt to beta oscillations are already commercially available. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Gap-junctional coupling measured by flow cytometry

A method is described which reliably quantifies the degree of intercellular communication via gap junctions by combining a dye-loading technique with fluorescence-activated flow cytometry. Our experiments expand former measurements of other groups by analyzing the time- and density-dependent onset of coupling with a fixed ratio of donor to recipient cells. The high sensitivity of this technique provides a better resolution than the microelectrode technique and allows the detection of small changes in gap-junctional coupling by examining a large number of cells in a single experiment. Suspended cells were loaded with the membrane-permeable dye calcein AM, which is intracellularly hydrolyzed by nonspecific esterases, and the resulting polyanionic calcein is thus trapped inside these donor cells. Gap junctions, however, are permeable for this fluorescent dye, as can be observed when suspended donor cells are added to recipient cells (i.e., monolayer cultures) in which case cell-cell contact is established within less than 60 min. In addition, one of these two cell populations can also be stained with a membrane-resident dye (e.g., DiI), which facilitates the identification of different cell populations (donors, recipients, and noncoupled cells) not only by epifluorescence microscopy but also by flow cytometry. Our analyses reveal that junctional coupling depends not only on the connexin type (homo- or heterotypic junction) but also on the origin (species) of the contacting cells (homo- or heterospecific contact). We confirm earlier reports in which homotypic-homospecific coupling was demonstrated with different techniques in connexin-transfected HeLa and RIN cells as well as in BICR/M1R(k) and 3T3/SV40 cells. In contrast to other publications, we show that a significant heterotypic-homospecific coupling between Cx40- and Cx43-HeLa transfectants can be resolved, whereas no coupling was detected for heterotypic-heterospecific contacts between Cx40-HeLa transfectants and the Cx43-expressing cell lines BICR/M1R(k), 3T3/SV40, and RIN.