8-12 HZ RHYTHMIC OSCILLATIONS IN HUMAN MOTOR CORTEX DURING 2-DIMENSIONAL ARM MOVEMENTS - EVIDENCE FOR REPRESENTATION OF KINEMATIC PARAMETERS

Direct cortical recordings were taken from 12 patients with implanted subdural electrode arrays during performance of a 2-dimensional, multi -joint, visually guided arm movement task. Task-related changes in the amplitude of the motor cortex 8-12 Hz surface local field oscillation s were evaluated for the encoding of direction and amplitude of moveme nt in the 6 patients in whom no epileptogenic or ECoG background abnor malities were detected over the motor-sensory cortical areas under the recording electrode array. The topography, time of onset and duration of these responses were evaluated in the context of motor cortex soma totopy, as defined by cortical stimulation delivered through the elect rode array. Multi-joint arm movements were accompanied by a decrease i n the power of the 8-12 Hz frequency components of the ECoG signal. Th ese power changes were spatially distributed over the upper extremity, motor-sensory representation. Movement amplitude influenced the magni tude, duration, and extent of the spatial distribution of ECoG power c hanges in the 8-12 Hz band. These effects occurred predominantly over cortical areas corresponding to the upper extremity motor-sensory repr esentations. Direction of movement had a weaker influence on the 8-12 Hz frequency components of the ECoG over the upper extremity motor-sen sory representations, but influenced the patterns of 8-12 Hz ECoG resp onse on adjacent cortical regions. These results show that the amplitu de of surface electrical oscillations generated over the rolandic cort ex are correlated with the kinematics of multi-joint arm movements. Th ese changes in the ECoG signal appear to reflect shifts in the functio nal state of neuronal ensembles involved in the initiation and executi on of motor tasks.