Figure 1.

Schematic diagram of the nine-hole box apparatus (a) and task requirements when response holes are configured to the left (b). The rat must sustain a nose poke in the center hole. After a variable delay, a brief light flash appeared in one of the two holes to the side of the rat. The rat then had to poke its nose into the same hole in which the light had appeared to obtain food reward (delivered at the rear of the chamber). (c) Experimental protocol. All animals were required to learn to perform the task to both the left and right sides. After surgery, animals in each of the three treatment groups (sham, lesion, graft) received one of two postoperative training regimes. Half of each group received 30 daily sessions on the ipsilateral side and then 30 daily sessions on the contralateral side (“Ipsi to Contra”) whereas the remaining animals received 30 contralateral sessions and then 30 ipsilateral sessions (“Contra to Ipsi”). Thus, performance on the contralateral side could be compared between the animals in each training regime to assess whether prior training on the ipsilateral side “transferred” to the contralateral side. All postoperative training commenced 4 months after graft surgery. The diagram outlines this procedure as if all surgery was performed on the right striatum, although the side of surgery was determined by the preoperative performance of each animal.