Baseline shifts do not predict attentional modulation of target processing during feature-based visual attention

Sean P Fannon

doi:10.3389/neuro.09.007.2007

Abstract

Cues that direct selective attention to a spatial location have been observed to increase baseline neural activity in visual areas that represent a to-be-attended stimulus location. Analogous attention-related baseline shifts have also been observed in response to attention-directing cues for non-spatial stimulus features. It has been proposed that baseline shifts with preparatory attention may serve as the mechanism by which attention modulates the responses to subsequent visual targets that match the attended location or feature. Using functional MRI, we localized color- and motion-sensitive visual areas in individual subjects and investigated the relationship between cue-induced baseline shifts and the subsequent attentional modulation of task-relevant target stimuli. Although attention-directing cues often led to increased background neural activity in feature specific visual areas, these increases were not correlated with either behavior in the task or subsequent attentional modulation of the visual targets. These findings cast doubt on the hypothesis that attention-related shifts in baseline neural activity result in selective sensory processing of visual targets during feature-based selective attention.

Highlights

IntroductionCovert visual attention to spatial locations or non-spatial features (e.g., color, shape, or motion) facilitates behavioral and neural responses elicited by attended stimuli (e.g., Corbetta et al, 1991; Heinze et al, 1994; Hillyard and Munte, 1984; Kingstone, 1992; Mangun and Hillyard, 1991; Moran and Desimone, 1985; Posner, 1980; Woldorff et al, 1997), and this facilitation is thought to reflect the top-down attentional control of sensory processing (Corbetta and Shulman, 2002; Desimone and Duncan, 1995; Mangun, 1995; Posner and Petersen, 1990)
We found that for both color and motion conditions, the specific feature cues improved sensitivity (A′) [for color, t(14) = 4.109, p = 0.001; for motion, t(14) = 2.367, p = 0.033] without influencing criterion (β) [for color, t(14) = −0.917, p = 0.375; for motion, t(14) = −1.379, p = 0.190]. These results demonstrate that subjects were actively using the cue information to help them perform the task, and that preparatory selective attention improved performance: When they were precued to a specific stimulus feature they were faster and more accurate in detecting that target feature than when they could not prepare for a specific target feature
Attention-related changes in pretarget neural activity have been reported in visual areas that process an attended location or feature

Summary

Introduction

Covert visual attention to spatial locations or non-spatial features (e.g., color, shape, or motion) facilitates behavioral and neural responses elicited by attended stimuli (e.g., Corbetta et al, 1991; Heinze et al, 1994; Hillyard and Munte, 1984; Kingstone, 1992; Mangun and Hillyard, 1991; Moran and Desimone, 1985; Posner, 1980; Woldorff et al, 1997), and this facilitation is thought to reflect the top-down attentional control of sensory processing (Corbetta and Shulman, 2002; Desimone and Duncan, 1995; Mangun, 1995; Posner and Petersen, 1990). How top-down attentional control enables selective stimulus processing remains an open question, but most models propose that attention modulates the excitability of the sensory neurons to facilitate the processing of attended stimuli, and perhaps to inhibit the activity of neurons coding unattended stimuli. If this is true, one would expect to observe changes in the background activity of sensory neurons with directed attention, even in the absence of sensory stimulation, and evidence for such effects of attention is growing.

Objectives

Methods

Results

Conclusion