Spontaneous alternation disturbance after lesions of the ventral mesencephalic tegmentum in the rat

Radiofrequency lesions of the ventral mesencephalic tegmentum (VMT), a region located above the nucleus interpeduncularis, provoked a disappearance of the spontaneous alternation behavior. The lesioned rats scores (44%) are not different from the chance level, while the alternation rate amounts to 77% in the control group. This disturbance cannot be explained by differences in the locomotor activity and choice latencies, nor by perseveration tendencies. The effects of VMT lesions appear to be of the same nature as those induced by limbic forebrain lesions. Anatomical connections between the VMT and the limbic system can explain these similarities.