Interaction of two "polarization" dominant foci in the mortor cortex.

The effects of sequential treatments (with intervals of 30-60 min) to weak anodic direct currents (0.5-3 microA) to the representation area of the fore- and hindlimbs of the motor cortex were studied in conscious, non-immobilized rabbits. This procedure created foci of excitation with the properties of dominants, i.e., distant stimuli (sound, light) produced responses corresponding to behavioral reactions (limb movement). During formation of the second dominant focus, linked inhibition of excitation foci was seen at different time points: there was long-term inhibition of the first dominant focus by the second, which was followed by reciprocal inhibition between the excitation foci, which resembled a mutual relationship. The interaction of the two "polarization" dominant foci, consisting of the transient dominance of one and then the other focus, persisted over a long time scale (more than 1 h) after the current inducing the foci was switched off. These results provide evidence of the redistribution of excitation within the motor apparatus during formation of dominant foci in the motor cortex.