Temporal dynamic of Tac1 expression during motor learning.

<p>Levels of Tac1 mRNA within M1 were measured using Real-Time RT-PCR in rats that were trained in a reaching task and related to an activity control at different time points. Tac1 expression was significantly elevated in learning rats seven hours after the training ended in the stage of skill acquisition (training session 1 and 2). This pattern was not observable at a later time-point (training session 6). *: p ≤ 0.05.</p

Injection of Substance P boosts motor learning.

<p>Injecting 1 μl Sub P into M1 before training session 1–3 (black arrows) significantly improves the performance gain when compared to controls. Injecting the same amount of Substance P to a time-point when animals reached plateau (grey arrows) has no effect. Thus, Substance P affects the acquisition but not execution of a skilled reaching task. Values are presented as mean ± SEM.</p

Injection of Substance P augments the encoding of motor memory at a very early stage.

<p>(A) top and bottom: to assess intra-session improvement of grasping performance, sessions were divided into quintile-bins. The percentage of successful grasps is plotted per bin. Intra-session improvement is indicated by blue (Saline) or red lines (Sub P). Injection of Sub P did not change intra-session improvement. Values are presented as mean ± SEM. Arrows indicate the time-point of injections. (B) top and bottom: The magnitude of decrease in performance between the end of a training session and the start of the subsequent session (inter-session development) is inversely correlated with the efficacy of motor memory retention. Sub P (filled circles, magenta lines) and Saline animals (open circles, green lines) are characterized by a nearly identical evolution of inter-session development except, the first value (i.e. between base and training session 1, red frame). There, a marked increment in performance occurred in Sub P animals consistent whereas a decrease is present in the Saline group. Values are presented as mean ± SEM. Arrows indicate the time-point of injections.</p