MULTICHANNEL DC CURRENT SOURCE DENSITY MAPPING OF THE BEREITSCHAFTSPOTENTIAL IN THE SUPPLEMENTARY AND PRIMARY MOTOR AREA PRECEDING DIFFERENTLY LOADED MOVEMENTS

The goal of the investigation using 23 normal subjects was to clarify (1) whether the pre-movement neuronal activation in form of the Bereit schaftspotential (BF) is different e.g., in topography for different i nertial loads onto a brisk finger extension, (2) if there is a differe nce, what kind of change is it, a global or regional one, (3) whether the early BP component (BP1) would be located in the fronto-central mi dline for finger extension with different loads, and (4) does the acti vation of the SMA occur prior to that of the primary motor area (MI). The BP preceding voluntary self-initiated extensions of the right inde x finger movement with different loads (low load task with 100g and hi gh load task with 200g) was recorded on the scalp using a 64 channel D C amplifier system. The Results showed: (1) Comparison of the two task s showed that amplitudes of the BP were significantly different in Cz and CP53. (2) The comparison of Cz with CP53 showed that the BP amplit udes were higher in Cz than in CP53 for both tasks, especially the BF1 component. (3) The comparison of the 3 motor areas (SMA, contralatera l and ipsilateral MI) showed that the BP was largest in the SMA and lo west in the ipsi- MI in both tasks. (4) The CSD laplacians showed that a clear current sink (=surface negativity) of the BP appeared on the scalp as early as 2.3 sec before EMG onset. The BP2 (a late component of BF following BP1 and starting about 0.5 sec prior to movement onset , which is lateralized towards the contralateral hemisphere) current s ink was lateralized in form of the contralateral preponderance of nega tivity (CPN). The location of the motor potential (MP) current sink wa s similar than that of BP2, but the areas and the densities were highe st. It is concluded that the more force is needed for finger extension against load, the larger the BP in motor areas. This constitutes a re gional rather than a global effect in preparation for voluntary moveme nt. The early BP component (BP1) started in the SMA, while BP2 and the MT were laterialized in form of the CFN. The activation of the SMA oc curred considerably earlier than the one of the MI.