**7. Conclusions**

*Neurostimulation and Neuromodulation in Contemporary Therapeutic Practice*

In our paper [51], the stump was stimulated by laser pulses (individual variabil-

inducing pinprick sensations. Twenty stimuli, whose intensity was established on the basis of the perceptive threshold of each patient, were delivered: we used a fixed intensity set at two times the individual sensory threshold, defined as the lower stimulus intensity that elicited a distinct painful pinprick sensation. In order to reduce both skin lesions and fatigue of peripheral nociceptors, the laser beam was shifted slightly by ~10 mm in a random direction between consecutive pulses [64]. Patients were reclined on a couch, wore protective goggles, and were instructed to keep their eyes open and gaze slightly downwards; they were requested to mentally count the number of stimuli, to keep their attention level constant. The interstimu-

*Non-painful (top row) phantom limb phenomena: changes in VAS scores overtime. Note that anodal ctDCS (black circles) significantly improved phantom movements and sensations compared to the sham condition (white squares). Data are given as percentage of baseline value ±1 S.D. At each time interval, the statistical significance refers to the comparison between anodal (active) and sham (placebo) stimulation (\*\*\*p < 0.001,* 

The main Aδ-LEP complex, N2/P2, and the earlier lateralized N1 component were recorded through standard disc, nonpolarizable Ag/AgCl surface electrodes (diameter 10 mm; BiomedVR, Florence, Italy). N2 and P2 components were recorded from the vertex (Cz), referenced to the earlobes; the N1 component was recorded from the contralateral temporal leads (T3 or T4), referenced to Fz [63]. The baseline-to-peak and the peak-to-peak amplitudes of N1 and N2/P2 components, respectively, were evaluated. Blinks and saccades were recorded with an EOG electrode placed on the supero-lateral right canthus connected to the system

Skin impedance was kept below 5 kΩ. An automatic artifact rejection system excluded all trials contaminated by transient signals exceeding the average value by

Cerebellar tDCS has still some limitations. First, the variability in outcome measures as well as the applied stimulation parameters across studies prompts further research about montage, duration, intensity of stimulation, electrodes number, and

Second, direct current stimulation may exert different, sometimes opposite, effects on motor and non-motor cerebellar functions; in this view, while studies exploring cognitive and emotional domains have used a classical monopolar configuration, others focusing on motor functions have adopted a different montage, in which the return electrode is positioned over the ipsilateral face. Only in the second case, tDCS has demonstrated long-lasting polarity-specific effects.

) with short duration (5 ms) and small diameter spots (5 mm),

**184**

placement.

ity: 15.75–24.91 J/cm2

**Figure 5.**

lus interval varied randomly between 15 and 30 s.

*Bonferroni post-hoc comparison; modified from [51], with permission).*

reference. Ground was placed on the mid-forehead.

±65 μV on each recording channel, including the EOG.

**6. Theoretical limitations to tDCS for cerebellar stimulation**

Cerebellar current stimulation represents an emerging, safe, and effective neuromodulation strategy for pain treatment. The possibility to interfere with cerebellar activity is particularly fascinating in the field of chronic pain syndromes, given that the cerebellum itself regulates both ascending and descending pathways involved in pain processing and nociception. However, the exact mechanisms of action are not fully understood, and some stimulation parameters have to be clearly defined, comprising duration, intensity, and charge density. Moreover, more attention will be deserved to combine and integrate different NIBS techniques, as well as different targets at the same time; for instance, by using the same device, cerebellar tDCS may be associate to spinal direct current polarization, in order to improve the clinical outcome and possibly extend putative effects over time.
