Abstract
The spectral power of intracranial field potentials shows movement-related modulations during reaching movements to different target positions that in frequencies up to the high-γ range (approximately 50 to above 200 Hz) can be reliably used for single-trial inference of movement parameters. However, identifying spectral power modulations suitable for single-trial analysis for non-invasive approaches remains a challenge. We recorded non-invasive electroencephalography (EEG) during a self-paced center-out and center-in arm movement task, resulting in eight reaching movement classes (four center-out, four center-in). We found distinct slow (≤5 Hz), μ (7.5–10 Hz), β (12.5–25 Hz), low-γ (approximately 27.5–50 Hz), and high-γ (above 50 Hz) movement onset- and end-related responses. Movement class-specific spectral power modulations were restricted to the β band at approximately 1 s after movement end and could be explained by the sensitivity of this response to different static, post-movement electromyography (EMG) levels. Based on the β band, significant single-trial inference of reaching movement endpoints was possible. The findings of the present study support the idea that single-trial decoding of different reaching movements from non-invasive EEG spectral power modulations is possible, but also suggest that the informative time window is after movement end and that the informative frequency range is restricted to the β band.
Highlights
Movement-related EEG responses have been investigated up to the β range, i.e., in frequencies below 30 Hz (Pfurtscheller et al, 1997)
As we have previously shown for the same data set (Ball et al, 2008), there are two peaks in the time course of the movementrelated high-γ response, one around movement onset and one around movement end
Due to the longer time window analyzed in the present as compared to the previous study, spectral power modulations occurring after movement end could be evaluated
Summary
Movement-related EEG responses have been investigated up to the β range, i.e., in frequencies below 30 Hz (Pfurtscheller et al, 1997). It has become evident that the motor cortex generates a broadbanded spectral power increase in the high-γ range, i.e., from approximately 50 Hz up to above 200 Hz (Crone et al, 1998; Miller et al, 2007). This movement-related high-γ response has been proposed to be closely related to cortical function, both in space and time, and is especially promising for investigating brain function and for potential brain–machine-interface (BMI) applications (Crone et al, 2006). It was demonstrated that, with optimized techniques, movement-related high-γ responses of the motor cortex are detectable non-invasively in the EEG (Ball et al, 2008; Darvas et al, 2010)
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