This distinction between exploration of task space

and reduction of variability Selleckchem Metformin at a chosen location in task space has been nicely demonstrated in a series of studies using a virtual ball and skittle task in humans (Cohen and Sternad, 2009 and Müller and Sternad, 2004). A paradigm recently introduced in adult songbirds induces short-term learning following song disruption (Andalman and Fee, 2009, Tumer and Brainard, 2007 and Warren et al., 2011). Specifically, it has been shown that playing white noise to the bird if the frequency of a specific syllable is within a prespecified range lead to song adjustments to avoid the white noise disruption. After learning in this paradigm, LMAN inactivation has shown to partially reverse the song adjustment (Andalman and Fee, 2009 and Warren

et al., 2011). We would argue that this behavior in birds is similar to error reduction in cerebellar patients (Criscimagna-Hemminger et al., 2010) and when binary reward is provided to healthy human subjects (Izawa and Shadmehr, 2011). In both cases, subjects use reward to select one movement over another but, critically, the newly selected movement is not executed any better than the original one. Similarly, in the songbird, syllable variability at the new frequency is the same, if not increased, compared to the initial frequency (Andalman and Fee, 2009 and Warren et al., 2011)—thus syllable production per se at the new frequency has not improved. It is of course possible whatever that improvement in song execution, motor skill, may occur during song acquisition but this buy Nutlin-3a has not been shown yet. We predict that this aspect of motor learning will be

a property of the song execution circuit rather than the BG circuit and could be investigated by tracking trial-to-trial variability during song practice after LMAN inactivation. Pallidotomy in humans, as a treatment for PD, is consistently associated with an impaired ability to learn new motor sequences (Brown et al., 2003 and Obeso et al., 2009). Thus, the unifying principle is that learning of sequential actions proceeds through trial and error, which is aided by the injection of variability by dopaminergic projections to BG, variability then decreases as the chosen successful action automatizes to a stereotypy (Costa, 2011). Our position so far is that the exploration-to-stereotypy view of sequential learning leaves out improvement in the quality of movement execution itself and that the birdsong literature has not yet shown evidence for the latter. In rodents, however, there is possibly some evidence that BG circuits play a role in task improvement through changes in the quality of movement execution. In the rotarod task, mice improve their ability to run for longer periods of time on an accelerating training wheel and this is associated with potentiation of synaptic strength in the striatum (Costa et al., 2004 and Yin et al., 2009).