Each measure is standardised to a mean of 10 and SD of 3. Procedural memory was assessed using a version of Nissen and Bullemer’s (1987) SRT Task. This task is designed to test implicit visuo-spatial sequence learning in procedural memory. In SRT tasks, participants are typically asked to press one of four response buttons, GSK2126458 in vitro each of which matches the location of a visual

stimulus presented on a computer monitor. Unbeknownst to participants, the visual stimulus follows a predefined sequence. After multiple exposures to the sequence, a random pattern of visual stimuli (rather than the predefined sequence) is presented. In neurologically intact children and adults, reaction times (RTs), which are the principal dependent measure of interest in SRT tasks, typically decrease during the repeated presentation of the sequence, and increase from the final sequence presentations to the random patterns (e.g., Nissen and Bullemer, 1987 and Thomas et al., 2004). This RT increase is taken as evidence that knowledge of the sequence has been learned. To determine whether the knowledge is purely implicit, explicit knowledge of the sequence is probed. Substantial neuroimaging and neurological evidence suggests that implicit sequence learning

in SRT depends on the procedural memory system (Knopman and Nissen, 1991, Siegert et al., 2006 and Thomas et al., 2004). For example, patients with neural pathology affecting the basal ganglia and cerebellum perform more poorly on implicit sequence learning than control groups, with the sequence-to-random increase either missing or decreased as compared Nutlin-3a supplier to controls (Knopman and Nissen, 1991, Nissen, 1992, Nissen and Bullemer, 1987, Nissen et al., 1989 and Siegert tuclazepam et al., 2006). Note that in the current study, unlike working and declarative memory, no verbal or auditory analogue of this task was

given to participants. This was, first of all, because auditory SRT tasks require participants to discriminate between tones of different frequencies (e.g., Zhuang et al., 1998), which might be problematic for children with SLI (Hill et al., 2005 and McArthur and Bishop, 2004). Additionally, our focus on a visuo-spatial SRT task was not considered to be problematic for testing the PDH, since, as we have seen above, the classic (and much more widely studied) visuo-spatial version of this task has been shown to depend on procedural memory structures, including those structures implicated by Ullman and Pierpont (2005). In the SRT Task used here, children were seated in front of a computer monitor, on which a visual stimulus (a yellow smiley face) repeatedly appeared in one of four horizontally arranged spatial locations. The children were instructed to press one of four horizontally arranged buttons (on a response box) that corresponded to each of the four locations on the screen. Presentation of the visual stimulus was divided into five blocks, each comprising 90 stimulus presentations.