Sequence and space: The critical role of a backward spatial span in the working memory deficit of visuospatial learning disabled children

The clinical use of backward spatial short-term memory tasks, and in particular of the Corsi backward task, has increased and has generated a series of theoretical hypotheses. For example, it has been argued that (in its comparison with the forward version) it has the same implications as the backward digit span and/or it requires the use of amodal central executive components of working memory. This research tested the hypotheses that the backward spatial span does not involve the controlled use of the same type of sequential spatial processing involved in the forward version, that its impairment is modality specific and that children with specific visuospatial learning disabilities (VSLD) have lower performance in backward than in forward Corsi block test, compared to a control group. In Study 1, participants were administered a verbal span test (Digit span test) and a visuospatial span test (Corsi blocks task) both in the forward and backward versions, while in Study 2 only the Corsi test was administered. The comparison between the forward and backward span versions showed that both visuo-spatial learning disabled children (VSLD) and controls presented with the Digit span had a lower performance with the backward version. However, for the Corsi task, this difference was present only for VSLD children. In fact, results revealed a significant impairment in the backward version of the Corsi test in the VSLD group, but not in the forward version, and in the Digit span tasks. Results suggest that the Corsi backward task is not the spatial analogue of the Digit backward task and that it involves specific spatial processes.