K(T(n)) is the selector matrix that selects the corresponding element in z(n) for the target T(n). At each trial, K(T(n)) z(n) represents BAY 73-4506 molecular weight the hand movement direction. The variable R(n) represents the rotation that was imposed; thus, y(n), computed

as the difference between R and z, represents the error in the visuomotor mapping (i.e., cursor error). The visuomotor mapping / states of the learner are updated by a generalization function B of size k by 1 that determines how much errors in one target direction affects mapping estimations in neighboring directions. In addition, the visuomotor mapping / states of the learner slowly forget at a rate determined by the scalar

A. To limit the number of ZD1839 supplier parameters in the simulations, we grouped targets in bins with 5° width. Thus, k = 16, including all training and probe targets. According to recently published estimations (Tanaka et al., 2009), we interpolated that B, a function of target-to-target angular difference, decreased its gain linearly from 0.09 to 0 within 9 target bins (i.e., a 45° directional window) and that A had a value of 0.98. The motor performance prediction by adaptation alone was simulated deterministically using these parameter values. We computed minimum sample sizes on assumed effect sizes for savings based on previously reported data (Zarahn et al., 2008). For an independent samples t test using a two-tailed alpha of 0.05 and power of 0.8, and assuming an effect size d = 1.9375

(computed based on previously reported group means and standard deviation; time constant = 0.47 for savings and 0.16 for naive, with SD = 0.16), the minimum first sample size is six subjects per group. The authors would like to thank Joern Diedrichsen, Sarah Hemminger, Valeria Della-Maggiore, Sophia Ryan, Reza Shadmehr, Lior Shmuelof, and Gregory Wayne for useful comments on the manuscript and Robert Sainburg for sharing experiment-control software. The study was supported by NIH grant R01NS052804 (J.W.K.) and funding from the Orentreich Foundation (J.W.K.). “
“Dopamine (DA) transmission by ventral midbrain neurons plays fundamental roles in voluntary motor function, habit learning, and motivation, while degeneration or dysregulation of these neurons is associated with Parkinson’s disease, schizophrenic psychosis, and drug addiction. How can a small number of neurons (300,000–600,000 in human, ∼45,000 in rat; German and Manaye, 1993) be responsible for so much? A study in this issue of Neuron provides the latest chapter in the study of what is turning out to be a complex set of personalities within this group of neurons ( Lammel et al., 2011).