Abstract
Microsaccade rates and directions were monitored while observers performed a visual working memory task at varying retinal eccentricities. We show that microsaccades generate no interference in a working memory task, indicating that spatial working memory is at least partially insulated from oculomotor activity. Intervening tasks during the memory interval affected microsaccade patterns; microsaccade frequency was consistently higher during concurrent spatial tapping (no visual component) than during exposure to dynamic visual noise (no task). Average microsaccade rate peaked after appearance of a fixation cross at the start of a trial, and dipped at cue onset and offset, consistent with previous results. Direction of stimuli in choice tasks did not influence microsaccade direction,however.
Highlights
In a informative study, Klauer & Zhou (2004) in experiments based on an existing paradigm (Tresch et al, 1993) isolated the distinction between visual and spatial STM from a number of alternative explanations
Relative to conditions without interference, movement discrimination affected dot location memory and color categorization interfered with ideogram memory
Single-cell (Andersen, 1989) and brain imaging (Corbetta et al, 1998) studies converge to the conclusion that this form of attention is implemented by a fronto-parietal network including some areas identified as relevant to Visual-Spatial Working Memory (VSWM) (Awh & Jonides, 2001; Corbetta, Kincade & Shulman, 2002)
Summary
Eleven UC Santa Cruz students completed the experiment for course credit. All were right-handed and two were female. A fixation cross (subtending 2°) appeared in the middle of the screen for 500 ms, followed by a cue stimulus in one of several positions for 400 ms. After cue offset a five second retention interval began, concluding in the presentation of a probe stimulus that remained visible until responded to in a two-alternative forced choice (2AFC) (Figure 1). Participants were asked to respond as quickly as possible to the probe while remaining very accurate. They were instructed to press the right key if the probe was in the same location as the cue, or the left key if shifted inward toward fixation.
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