## 4 Cerebellum and Anticipatory Postural Control  
The contribution of the cerebellum to APA regulation (Figure 1) has been deeply documented. In 2005, [PERSON] et al. [60] studied APAs associated with the \"barman task\" in patients with unilateral or bilateral cerebellar damage. In this bimanual movement, subjects supported an object with one hand, while they had to lift the object voluntarily with the other hand (active lifting) or the object was lifted by an experimenter (passive lifting). In healthy subjects, when the object was lifted by the other hand, an inhibitory APA chain was observed, synchronous to the recruitment of the prime mover and preceding the lifting. However, when the object was unexpectedly lifted by an external force (by the experimenter), an impaired balance of the arm occurred, which could only be compensated by a sensory feedback, a postural reflex [61]. Therefore, the APA feedforward command, generated during the active lifting, allowed greater stabilization of balance. On the contrary, patients with cerebellar damage showed poorly timed adjustments, with the APAs beginning earlier than in healthy participants, confirming the essential role played by the cerebellum in timing motor sequences [12; 13] and extending it also to the context of the feedforward APA control. Moreover, in this work, it has been reported that cerebellar damage abolished APA \"plasticity\" since these patients were unable to learn new APA schemes. This evidence suggests the engagement of the cerebellum not only in the predictive but also in the adaptive control of motor timing (Figure 1). As stated before, inter-limb APAs are evident in gait initiation. Literature showed altered gait initiation in several neurological dysfunctions characterized by poor motor control [62; 63] and in particular, in pathologies involving the cerebellum. For example, [PERSON] and [PERSON] (2001) [64] described adults with cerebellar deficits showing reduced force production, length, and velocity of the first step, accompanied by impairments in the use of predictive information to adapt APAs to the mechanical needs of gait initiation. More recently, [PERSON] et al. (2017) [65] tested the involvement of the SMA-pontine-cerebello-thalamo-cortical pathway in gait initiation throughout a technique of repetitive transcranial magnetic stimulation, called continuous theta burst stimulation (cTBS), which is able to consistently reduce motor cortical excitability with long-term depression effects [66]. The cTBS functional inhibition over the cerebellum showed a considerable role of this structure in the muscle coordination, as well as in coupling between the anticipatory postural control and the execution phase during gait initiation. Literature regarding cerebellar control in intra-limb APA is generally poor. In this regard, it is worth recalling that cerebellar damage altered timing and amplitude scale of muscular activity during arm movements [67; 68] and that patients with acute cerebellar lesions did not show a normal intra-limb anticipatory adjustment in unimanual motor tasks, like in grip force when lifting or moving an object [69; 70]. In this regard, [PERSON] et al. (2015) [71] focused on the involvement of the cerebellum in intra-limb APAs, testing the postural chain that stabilizes the arm during a brisk index-finger flexion [33] in atax adult patients. Electromyography recordings of postural muscles were analyzed in a group of adult subjects with a slowly progressive adult-onset cerebellar syndrome and then compared with those from a group of age-matched healthy subjects. Results showed that the intra-limb APA pattern associated with the index-finger flexion remained unchanged between the two groups, while a timing disruption of intra-limb APAs occurred in atax patients. The delayed APAs described in [PERSON]'s work are in line with those found by [PERSON] at al. (2013) [72] in transgenic Spinocerebellar ataxic mice.