Spatial layout of letters in nonwords affects visual short-term memory load: Evidence from human electrophysiology


  • This research was made possible by a grant from the Natural Sciences and Engineering Research Council of Canada awarded to PJ, by a grant from the Canadian Institutes of Health Research awarded to PJ, by equipment funded by the Canada Fund for Innovation awarded to PJ, by the Canada Research Chairs program, by infrastructure support from the Fonds Quebécois pour la Recherche en Santé du Québec, by a team research grant from the Fonds Québecois pour la Recherche sur la Nature et la Technologie awarded to MA, FG, and PJ, and by research support from Université de Montréal.

Address correspondence to: David J. Prime, Department of Psychology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada, V5A 1S6. E-mail:


The sustained posterior contralateral negativity (SPCN) was used to investigate the effect of spatial layout on the maintenance of letters in VSTM. SPCN amplitude was measured for words, nonwords, and scrambled nonwords. We reexamined the effects of spatial layout of letters on SPCN amplitude in a design that equated the mean frequency of use of each position. Scrambled letters that did not form words elicited a larger SPCN than either words or nonwords, indicating lower VSTM load for nonwords presented in a typical horizontal array than the load observed for the same letters presented in spatially scrambled locations. In contrast, prior research has shown that the spatial extent of arrays of simple stimuli did not influence the amplitude of the SPCN. Thus, the present results indicate the existence of encoding and VSTM maintenance mechanisms specific to letter and word processing.