Academic journal article Psychonomic Bulletin & Review

Spatial Resolution in Visual Memory

Academic journal article Psychonomic Bulletin & Review

Spatial Resolution in Visual Memory

Article excerpt

Published online: 12 August 2014

© Psychonomic Society, Inc. 2014

Abstract Representations in visual short-term memory are considered to contain relatively elaborated information on object structure. Conversely, representations in earlier stages of the visual hierarchy are thought to be dominated by a sensory-based, feed-forward buildup of information. In four experiments, we compared the spatial resolution of different object properties between two points in time along the processing hierarchy in visual short-term memory. Subjects were asked either to estimate the distance between objects or to estimate the size of one of the objects' features under two experimental conditions, of either a short or a long delay period between the presentation of the target stimulus and the probe. When different objects were referred to, similar spatial resolution was found for the two delay periods, suggesting that initial processing stages are sensitive to objectbased properties. Conversely, superior resolution was found for the short, as compared with the long, delay when features were referred to. These findings suggest that initial representations in visual memory are hybrid in that they allow finegrained resolution for object features alongside normal visual sensitivity to the segregation between objects. The findings are also discussed in reference to the distinction made in earlier studies between visual short-term memory and iconic memory.

Keywords Perceptual organization · Visual working memory · Object-based attention · Short term memory

The neural architecture that mediates our perceptual experience is thought to be a combination of a serial feed-forward buildup of information alongside top-down feedback influences of context, experience, and expectations. It has been shown that the effects of top-down information on visual representations can be traced to relatively early stages of the perceptual stream (Ben-Shalom & Ganel, 2012; Fang, Boyaci, Kersten, & Murray, 2008; Murray, Boyaci, & Kersten, 2006; Vandenbroucke, Sligte, Fahrenfort, Ambroziak, & Lamme, 2012). Yet the exact nature of the top-down influences on visual memory is yet to be explored. Indeed, current models of visual memory still propose that sensory memory is governed by feed-forward information that mainly relates to the sensory input (Biederman, 1985;Marr,1982; Riesenhuber & Poggio, 2000).

Visual working memory (VWM) is considered to contain relatively advanced visual representations that are potentially available to consciousness (Dehaene & Naccache, 2001; Todd &Marois,2004; Vogel, Woodmen, & Luck, 2001). Conversely, earlier representations in visual memory are considered to be more perceptual in nature and are less likely to gain conscious awareness (Coltheart, 1980; Long, 1980). It is therefore assumed that visual information is processed differently at different time points along the hierarchy of visual short-term memory (Coltheart, 1980; Di Lollo & Dixon, 1988; Irwin & Yeomans, 1986; Long, 1980). The purpose of the present study was to learn more about the nature of these processing stages by looking at the spatial resolution in visual memory at different points in time along the processing hierarchy.

The results of more recent studies strongly suggest that early representations in visual memory are not constructed on the basis of the visual input alone but are affected by top-down processing. For example, it has been shown that different types of size-contrast and depth-based visual illusions affect performance in short delay periods to the same extent that they affect performance after longer delays. In a recent study from our lab (Ben-Shalom & Ganel, 2012), we showed that visual illusions that are triggered by the relational properties between objects distort size perception both in early and in late processing stages along the visual hierarchy. In this study, we used two different points in time to probe early and late processing stages. …

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