However, the response of the population is balanced across different behavioral conditions so that the FEFSEM as a whole is always making the same contribution to the smooth eye movement. A similar conclusion has been reached for the cerebellar floccular complex (Kahlon and Lisberger, 2000 and Medina and Lisberger, 2009). Finally, we characterized differences in the temporal preferences of neurons activated by learning versus by the mimic stimulus. For our dataset of 21 neurons, the correlation between neural

check details preference and the size of the learned neural response reached a peak when the neural preference was taken at 250 ms (Figure 6, gray trace), as expected. In contrast, the correlation between neural preference and the size of the mimic response reached a SB203580 order peak for neural preference earlier in the trial (Figure 6, black trace), suggesting that the mimic target motion was most effective for neurons that preferred times

during the initiation of pursuit. Previous studies have suggested that motor learning occurs on multiple time scales (Lee and Schweighofer, 2009, Ethier et al., 2008 and Smith et al., 2006), including situations where the behavior on a given trial reflects the instruction provided on the previous trial (Yang and Lisberger, 2010). To measure the relative contributions of single-trial versus longer-term learning processes to the behavioral and neural changes reported here, we sorted learning trials based on the identity of the immediately preceding trial. The size of the learned eye velocity was smaller if it had been preceded by a control trial versus by another learning trial. The effect averaged

7.1% and 21.5% in Monkeys S and G and was statistically significant in 15.6% (7/45, Monkey Ketanserin S) and 61.8% (34/55, Monkey G) of the learning experiments in the two monkeys (Mann-Whitney U test, p < 0.05). The small trial-over-trial changes in the size of behavioral learning frequently were not present in a similar analysis of the size of neural learning (for example, Figure 7A). In the 35 neurons that showed a significant change in mean firing rate as a result of learning, the trial-over-trial changes in neural learning were distributed fairly evenly above and below zero, and were unrelated to the trial-over-trial learning of eye velocity (Figure 7B). The neural response on learning trials preceded by a control trial was on average 2.1% bigger (Monkey S) and 4.4% smaller (Monkey G) than those preceded by another learning trial. Neural response differences were statistically significant in 15.0% (3/20, Monkey S) and 6.7% (1/15, Monkey G) of the neurons (Mann-Whitney U test, p < 0.05). We conclude that the neural learning in the FEFSEM results from a longer-term process that does not contribute to trial-over-trial changes in the learned behavior.