Abstract
Prior studies have shown that spatial attention modulates early visual cortex retinotopically, resulting in enhanced processing of external perceptual representations. However, it is not clear whether the same visual areas are modulated when attention is focused on, and shifted within a working memory representation. In the current fMRI study participants were asked to memorize an array containing four stimuli. After a delay, participants were presented with a verbal cue instructing them to actively maintain the location of one of the stimuli in working memory. Additionally, on a number of trials a second verbal cue instructed participants to switch attention to the location of another stimulus within the memorized representation. Results of the study showed that changes in the BOLD pattern closely followed the locus of attention within the working memory representation. A decrease in BOLD-activity (V1–V3) was observed at ROIs coding a memory location when participants switched away from this location, whereas an increase was observed when participants switched towards this location. Continuous increased activity was obtained at the memorized location when participants did not switch. This study shows that shifting attention within memory representations activates the earliest parts of visual cortex (including V1) in a retinotopic fashion. We conclude that even in the absence of visual stimulation, early visual areas support shifting of attention within memorized representations, similar to when attention is shifted in the outside world. The relationship between visual working memory and visual mental imagery is discussed in light of the current findings.
Highlights
Spatial attention is the ability to dynamically allocate processing resources to a limited part of the visual environment [1,2,3]
We investigated whether shifting attention within a working memory representation in the absence of visual stimulation would activate low-level visual cortical areas coding the relevant memorized locations
The results of this study show that modulation of the blood oxygen level dependent (BOLD) signal corresponds to the attended location currently active in working memory
Summary
Spatial attention is the ability to dynamically allocate processing resources to a limited part of the visual environment [1,2,3]. Prior studies have shown that in order to facilitate the selection of relevant visual information needed for the observer’s current goals, attention is used to bias perceptual processing of external visual representations of objects or locations. This model of ‘‘sensory gain’’ has been motivated by studies that showed increased neural activity in visual areas as a direct result of focused attention. Allocating attention to regions in the visual field has shown to modulate neural activity in both striate and extrastriate cortex in a retinotopic fashion [12,13,14]. When attention is allocated to objects or locations in the visual field, the perceptual representation of this information is enhanced as indexed by increased neural activity in visual areas that code the attended information
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