Puberty: a period of both organizational and activational effects of steroid hormones on neurobehavioural development.

During perinatal development, steroid hormones act on the central nervous system (CNS) to organize neural circuits. These circuits remain relatively dormant until hormonal stimulation received in adulthood acts on the CNS to activate adult reproductive physiology and behaviour. In this review, the proposal is put forward that, in addition to perinatal development, puberty serves as another period of neural maturation mediated by both steroid-dependent and -independent events that further organize and shape the behavioural potential of the adult organism. In support of this thesis, data are summarized that clearly show the organizational effects of the pubertal rise in gonadal hormones on mating behaviour and other steroid-mediated behaviours exhibited in adulthood, and on the neural pathways that mediate these behaviours. The importance of determining whether this sensitive period of neural development during puberty is a 'critical period' is also discussed, as well as whether perturbations of the nervous system during pubertal development may result in negative behavioural and physiological outcomes in adulthood. It is concluded that puberty is not merely a time when increasing levels of gonadal steroids activate the neural circuits organized during perinatal development, but also a time of further organization of the CNS, which allows for appropriate behaviours to emerge in adulthood.