Movement-related potentials preceding toe plantarflexion and dorsiflexion.

The cerebral potentials associated with self-paced rapid dorsiflexion and plantarflexion of the left toes were compared in the same experiment using 10 subjects 5 of whom were female and 5 of whom were male. The EEG was recorded from C3, C1, Cz, C2 and C4 including computed bipolar recordings C4/C3 and C2/C1. For both kinds of movements, the Bereitschaftspotential (BP) or readiness potential was bilaterally symmetrical in the first half of the foreperiod. In the later foreperiod, an ipsilateral preponderance of negativity (IPN) developed. The direction of toe movement had no effect on the IPN. The etiology of the paradoxical BP side preponderance prior to toe movements is discussed which can probably be referred to the unique dipole orientation of a generator situated on the mesial cortical surface in the depth of the interhemispherical fissure.