Functional dissociation of lower and upper frequency mu rhythms in relation to voluntary limb movement.
OBJECTIVE
The goal of this study is to investigate the reactivity of central rhythms in the alpha band during self-paced voluntary finger and foot movement and to give an answer to the question, whether different types of mu rhythms exist.


METHODS
The effect of self-paced, voluntary finger and foot movement was studied in a group of 12 right-handed healthy volunteers. The EEG was recorded from a grid of 34 electrodes placed over sensorimotor areas with inter-electrode distances of approximately 2.5 cm. The event-related desynchronization (ERD) was quantified in the 8-10 and 10-12 Hz bands.


RESULTS
Both frequency components are blocked prior to and during movement and therefore, they have to be considered as mu rhythms. The lower frequency component results in a widespread movement-type non-specific ERD pattern, whereas the upper frequency component shows a more focused and movement-type specific pattern, clearly different with finger and foot movement.


CONCLUSIONS
The distinct reactivity patterns provide evidence for the existence of two types of mu rhythms, a somatotopically non-specific lower frequency mu rhythm and a somatotopically specific mu rhythm characteristically found in the upper alpha frequency band.
Pfurtscheller
G
G
Department of Medical Informatics, Institute of Biomedical Engineering, University of Technology Graz, Inffeldgasse 16a/II, A-8010, Graz, Austria. pfu@dpmi.tu-graz.ac.at
Neuper
C
C
Krausz
G
G
D000328:Adult; D000704:Analysis of Variance; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D003344:Cortical Synchronization; D004569:Electroencephalography; D005121:Extremities / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*