Central
mechanisms, both supraspinal and spinal, play an important role in erectile function.
A 'natural' erection is initiated in the brain as a result of sexual stimuli
which require processing and integration in order to initiate an appropriate
erectile response. Visual, olfactory, tactile and imaginative stimuli from the
occipital lobe, rhinencephalon, thalamus and limbic system, respectively, are
integrated and processed into erectile responses in two small hypothalamic
nuclei, the paraventricular nucleus (PVN) and medial preoptic area (MPOA). The
role of the MPOA is to recognize sensory stimuli from
the higher brain centers
and integrate them with sexual motivation and copulatory motor programmes,
(McKenna,1998), while PVN plays a key role in the erectile response (Eaton et al.,1991).