On the requirement of postural asymmetry for rotational behaviour.

Focal, unilateral injection of muscimol into the rat substantia nigra, pars reticulata evoked two outwardly different forms of contraversive rotation. In the first (and most common) type of circling, animals adopted a tight curvature of the whole head and body about the longitudinal axis and propelled themselves primarily with their forelimbs. In other cases, little if any postural asymmetry was present during rotation in equivalent diameter circles created by use of both fore- and hindlimbs. Each profile correlated with the nigral locus injected. It is reiterated that postural asymmetry is not essential for rotation.