Previously we have demonstrated, that the contralateral optokinetic (visual) stimulation (COS) induces an inversion of goldfish motor asymmetry and three-fold decrease of the ventral dendrite of ipsilateral Mauthner neuron (MN) volume, whereas repetitive in training mode daily COS sessions induced a motor behavior resistance to this influence in fish. In the present investigation we have examined the effect of the training COS sessions on the structure of MN and their parts. It was found that daily visual training stabilizes the size of the ventral dendrites, significantly increasing their resistance to single prolonged COS. Thus, the adapted morpho-functional state was induced in the individual dendrite and in the whole neuron by repetitive stimulation of that dendrite. These results make it possible to investigate in more detail the role of an individual dendrite in the modification of functional activity of the whole neuron and in adaptation and memory mechanisms at the cellular level.