Tanoue RT, Jones KT, Peterson DP, Berryhill ME (2013). Pre- and retro-cueing differentially rely on prefrontal activations: a tDCS investigation...

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Tanoue RT, Jones KT, Peterson DP, Berryhill ME (2013). Pre- and retro-cueing differentially rely on prefrontal activations: a tDCS investigation. Brain Stimulation, 6, 675-682.
[ DOI: 10.1016/j.brs.2012.11.003. PMCID: PMC3608701. ]

Abstract

Background: Perceptual attention enhances the processing of items in the environment, whereas internal attention enhances processing of items encoded in visual working memory. In perceptual and internal attention cueing paradigms, cues indicate the to-be-probed item before (pre-cueing) or after (retro-cueing) the memory display, respectively. Pre- and retro-cues confer similar behavioral accuracy benefits (pre-: 14e19%, retro-: 11e17%) and neuroimaging data show that they activate overlapping frontoparietal networks. Yet reports of behavioral and neuroimaging differences suggest that pre- and retro-cueing differentially recruit frontal and parietal cortices (Lepsien and Nobre, 2006).

Objective/hypothesis: This study examined whether perceptual and internal attention are equally disrupted by neurostimulation to frontal and parietal cortices. We hypothesized that neurostimulation applied to frontal cortex would disrupt internal attention to a greater extent than perceptual attention. Methods: Cathodal transcranial direct current stimulation (tDCS) was applied to frontal or parietal cortices. After stimulation, participants completed a change detection task coupled with either pre- or retro-cues.

Results: Cathodal tDCS across site (frontal, parietal) hindered performance. However, frontal tDCS had a greater negative impact on the retro-cued trials demonstrating greater frontal involvement during shifts of internal attention.
Conclusions: These results complement the neuroimaging data and provide further evidence suggesting that perceptual and internal attention are not identical processes. We conclude that although internal and perceptual attention are mediated by similar frontoparietal networks, the weight of contribution of these structures differs, with internal attention relying more heavily on the frontal cortex. 

Tanoue RT, Berryhill ME (2012). The mental wormhole: Internal attention shifts without regard for distance. Attention, Perception & Psychophysics, 74, 6, 1199-1215. [ DOI: 10.3758/s1341401203050. ]

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Abstract

Attention operates perceptually on items in the environment, and internally on objects in visuospatial working memory. In the present study, we investigated whether spatial and temporal constraints affecting endogenous perceptual attention extend to internal attention. A retro-cue paradigm in which a cue is presented beyond the range of iconic memory and after stimulus encoding was used to manipulate shifts of internal attention. Participants' memories were tested for colored circles (Experiments 1, 2, 3a, 4) or for novel shapes (Experiment 3b) and their locations within an array. In these experiments, the time to shift internal attention (Experiments 1 and 3) and the eccentricity of encoded objects (Experiments 2-4) were manipulated. Our data showed that, unlike endogenous perceptual attention, internal shifts of attention are not modulated by stimulus eccentricity. Across several timing parameters and stimuli, we found that shifts of internal attention require a minimum quantal amount of time regardless of the object eccentricity at encoding. Our findings are consistent with the view that internal attention operates on objects whose spatial information is represented in relative terms. Although endogenous perceptual attention abides by the laws of space and time, internal attention can shift across spatial representations without regard for physical distance.