New publication

"Brain electrical microstate features as biomarkers of a stable motor output"

Figure: Example of an experimental trial: periods of isometric contraction, while the subject pressed the bulb (upper panel), were intermingled with periods of rest. In the middle panel, there is an example of the exerted force, as measured by the pressure sensor inside the bulb. The force is expressed as the percentage of the maximal voluntary contraction force (MVC). In the bottom panel, the sequence of the visual stimulus provided to the subject during the task: the position of the vertical black line corresponded to the exerted force. The requested level of contraction was indicated by the two horizontal black lines at the sides of the vertical green bar.

The aim of the present study was to elucidate the brain dynamics underlying the maintenance of a constant force level exerted during a visually guided isometric contraction task by optimizing a predictive multivariate model based on global and spectral brain dynamics features.
Electroencephalography (EEG) was acquired in 18 subjects who were asked to press a bulb and maintain a constant force level, indicated by a bar on a screen. For intervals of 500 ms, we calculated an index of force stability as well as indices of brain dynamics: microstate metrics (duration, occurrence, global explained variance, directional predominance) and EEG spectral amplitudes in the theta, low alpha, high alpha and beta bands. We optimized a multivariate regression model (partial least square (PLS)) where the microstate features and the spectral amplitudes were the input variables and the indexes of force stability were the output variables. The issues related to the collinearity among the input variables and to the generalizability of the model were addressed using PLS in a nested cross-validation approach.
The optimized PLS regression model reached a good generalizability and succeeded to show the predictive value of microstates and spectral features in inferring the stability of the exerted force. Longer duration and higher occurrence of microstates, associated with visual and executive control networks, corresponded to better contraction performances, in agreement with the role played by the visual system and executive control network for visuo-motor integration. Significance. A combination of microstate metrics and brain rhythm amplitudes could be considered as biomarkers of a stable visually guided motor output not only at a group level, but also at an individual level. Our results may play an important role for a better understanding of the motor control in single trials or in real-time applications as well as in the study of motor control.

Croce, P.; Tecchio, F.; Tamburro, G.; Fiedler, P.; Comani, S.; Zappasodi, F.:
Brain electrical microstate features as biomarkers of a stable motor output. Journal of Neural Engineering 2022, 19, 056042.


Contact:    Jun.-Prof. Dr.-Ing. Patrique Fiedler