The ability to interact with challenging environments requires co-ordination of sensory and motor systems that drive appropriate defence behaviours. The ventrolateral midbrain periaqueductal grey (vlPAG) lies at the heart of the defence-arousal system and its integrity is paramount to the expression of defence behaviours (1). To date, attention has focused on the sensory consequences of vlPAG activation, as part of co-ordinated passive coping strategies triggered by inescapable stressors (2). Work from this laboratory has shown that chemical activation of descending pathways from the vlPAG powerfully modulates responses of spinal neurones to cutaneous mechanical and thermal (heat and cold) stimulation, in vivo (3-5). Of relevance to survival, in naïve animals generalised activation of the PAG selectively inhibits spinal nociceptive processing, as compared to non-noxious cutaneous transmission. This pattern of response is thought to support defence behaviour by filtering out nociceptive input that could distract an animal from carrying out behaviours necessary for survival and leaves intact transmission of non-noxious information that provides precise information with the capacity to direct motor activity and promote survival. Despite the fundamental importance of motor behaviours evoked from the vlPAG, very little is known about their underlying neural pathways and mechanisms. As a first step, this significant gap in understanding was addressed by (i) reports that activation of the vlPAG enhances α-motoneuron excitability which, it is proposed, underlies fear-evoked freezing behaviour (6-7) and (ii) the demonstration that these effects are dependent, at least in part, on the integrity of the cerebellum (6); the largest sensorimotor structure in the brain. Furthermore, vlPAG-modulation of sensory transmission in motor circuits was evidenced by inhibition of peripheral nerve-evoked cerebellar cortical field potentials, which from individual PAG stimulation sites, was accompanied by facilitation of spinal motor outflow (as assessed by α-motoneuron excitability; (7)). These studies provided initial insights into the pathways and mechanisms that mediate co-ordination by the vlPAG of sensory and motor processing in survival networks Our demonstration that survival networks include interactions between the vlPAG and the cerebellum led us to investigate the effects of descending control from the vlPAG on a pre-cerebellar sensory pathway originating in the spinal cord; the spino-olivary tract. Consistent with our previous studies of descending control of spinal nociception, activation of the vlPAG selectively inhibited the cutaneous nociceptor- (as compared with non-nociceptor) evoked responses of antidromically identified spino-olivary neurons. However, a novel and important finding was the facilitation of proprioceptive responses of spino-olivary neurons (7). This raises the possibility that cerebellar input from spinal circuits signaling limb position and movement can be enhanced, thus refining sensory inputs that direct motor control. Such an effect is entirely consistent with a role for the vlPAG in co-ordinating motor behaviours in defence situations. Taken together, our studies provide strong evidence that the vlPAG can orchestrate differential changes in ascending sensorimotor projections and spinal motor systems simultaneously. We suggest that this differential gating of nociceptive cutaneous and proprioceptive information to the cerebellum by the vlPAG, together with the enhancement of motor outflow may promote a condition in which the animal is ready (enhanced proprioceptive input and increased muscle activity) and able to escape (less likely to be perturbed by noxious sensory information), thus assisting survival.