Understanding and Modulating Motor Learning with Cerebellar Stimulation

Abstract

Non-invasive brain stimulation techniques are a powerful approach to investigate the physiology and function of the central nervous system. Recent years have seen numerous investigations delivering transcranial magnetic stimulation (TMS) and or transcranial direct current stimulation (tDCS) to the cerebellum to determine its role in motor, cognitive and emotional behaviours. Early studies have shown that it is possible to assess cerebellar-motor cortex (CB-M1) connectivity using a paired-pulse TMS paradigm called cerebellar inhibition (CBI), and indirectly infer the state of cerebellar excitability. Thus, it has been shown that CBI changes proportionally to the magnitude of locomotor learning and in association with reaching adaption tasks. In addition, CBI has been used to demonstrate at a physiological level the effects of applying TMS or tDCS to modulate, up or down, the excitability of cerebellar-M1 connectivity. These studies became the fundamental substrate to newer investigations showing that we can affect motor, cognitive and emotional behaviour when TMS or tDCS targeting the cerebellum is delivered in the context of performance. Furthermore, newer investigations are starting to report the effects of cerebellar non-invasive stimulation to treat symptoms associated with neurological conditions such as stroke and dystonia. Altogether, non-invasive cerebellar stimulation can potentially become a game changer for the management of conditions that affect the cerebellum given the scarcity of current effective therapeutic options. In this brief manuscript, some of the current evidence demonstrating the effects of cerebellar stimulation to modulate motor behaviour and its use to assess physiological processes underlying motor learning are presented.

Young stellar clusters in the Rosette molecular cloud

“…Celnik (1985) observed the radio recombination line in the Rosette Hii and showed the nebula is ionization bound, which suggests that Appendix A is available in electronic form at http://www.aanda.org…”

Planckintermediate results

“…2a shows the Rosette H ii region and its nearly circular shape. We fit the radial profile of the RRL emission with a shell model and find the same values as Celnik (1985) for the inner and outer radii, r H ii in = 7 pc and r H ii out = 19 pc, respectively, with an uncertainty of 1 pc. Also shown in Fig.…”

“…Celnik (1985) estimated the size of the nebula by fitting several shell models to observations at 1.4 and 4.7 GHz. The mean radial profile of the radio emission was reproduced by a model of a spherical shell with inner and outer radii of 7 and 19 pc, respectively, and constant electron density of 13.5 cm −3 (these values have been scaled from the distance of 1.42 kpc used by Celnik to the adopted distance of 1.6 kpc).…”

“…5. The size of the shell can be estimated by fitting the Planck intensity map with a shell model, similar to that used by Celnik (1985) to derive the radius of the ionized nebula. We obtain r dust in = 18 pc and r dust out = 22 pc for the inner and outer radii of the dust shell, with a typical uncertainty of 2 pc.…”

The theory of globulettes: candidate precursors of brown dwarfs and free-floating planets in H ii regions

“…Doing so over a range of masses yields the theoretical massradius relation for globulettes. In Figure 2 the solid black line shows our theoretical mass-radius relation for an external pressure Pext = nkBT , where the electron density n in the H ii region is 10 cm −3 , and the average temperature of the ionized gas is 5800 K (that estimated for the Rosette by Celnik 1985 Gahm et al 2007). These pressure confined Bonnor-Ebert spheres are not very stratified, having a broad interior region of slowly varying density until close to the globulette boundary (c.f.…”