Limits...
Pre-stimulus activity predicts the winner of top-down vs. bottom-up attentional selection.

Mazaheri A, DiQuattro NE, Bengson J, Geng JJ - PLoS ONE (2011)

Bottom Line: Our ability to process visual information is fundamentally limited.This leads to competition between sensory information that is relevant for top-down goals and sensory information that is perceptually salient, but task-irrelevant.We propose that the high frontal alpha reflects a disengagement of attentional control whereas the transient posterior alpha time-locked to the saccade indicates sensory inhibition of the salient distractor and suppression of bottom-up oculomotor capture.

View Article: PubMed Central - PubMed

Affiliation: Center for Mind and Brain, University of California Davis, Davis, California, United States of America. a.mazaheri@donders.ru.nl

ABSTRACT
Our ability to process visual information is fundamentally limited. This leads to competition between sensory information that is relevant for top-down goals and sensory information that is perceptually salient, but task-irrelevant. The aim of the present study was to identify, from EEG recordings, pre-stimulus and pre-saccadic neural activity that could predict whether top-down or bottom-up processes would win the competition for attention on a trial-by-trial basis. We employed a visual search paradigm in which a lateralized low contrast target appeared alone, or with a low (i.e., non-salient) or high contrast (i.e., salient) distractor. Trials with a salient distractor were of primary interest due to the strong competition between top-down knowledge and bottom-up attentional capture. Our results demonstrated that 1) in the 1-sec pre-stimulus interval, frontal alpha (8-12 Hz) activity was higher on trials where the salient distractor captured attention and the first saccade (bottom-up win); and 2) there was a transient pre-saccadic increase in posterior-parietal alpha (7-8 Hz) activity on trials where the first saccade went to the target (top-down win). We propose that the high frontal alpha reflects a disengagement of attentional control whereas the transient posterior alpha time-locked to the saccade indicates sensory inhibition of the salient distractor and suppression of bottom-up oculomotor capture.

Show MeSH

Related in: MedlinePlus

Example trial procedure.Each trial began with a blink of the fixation diamond. After a jittered interval, the visual search items appeared (illustrated here by a target in the left visual field) and subjects were free to move their eyes and indicate whether the target “t” was upright or inverted. Targets appeared alone, with a neutral distractor, or a salient distractor. Note that items are not drawn to scale for illustrative clarity.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3046127&req=5

pone-0016243-g001: Example trial procedure.Each trial began with a blink of the fixation diamond. After a jittered interval, the visual search items appeared (illustrated here by a target in the left visual field) and subjects were free to move their eyes and indicate whether the target “t” was upright or inverted. Targets appeared alone, with a neutral distractor, or a salient distractor. Note that items are not drawn to scale for illustrative clarity.

Mentions: Stimuli were composed of a ‘t’-like stimulus superimposed on a square background ( Fig. 1). Target stimuli were defined as an upright or inverted “t” and were located randomly in the left or right lower visual field (6.3° of horizontal and vertical visual angle from fixation). Targets subtended approximately .9° of visual angle at fixation. The distractor stimuli (90° rotations of target) were either low contrast (Michelson Contrast Ratio = .51; foreground luminance = 5.4 cd/m2, background luminance = 16.8 cd/m2) or high contrast (Michelson Contrast Ratio = .96; foreground luminance = .54 cd/m2, background luminance = 30.5 cd/m2); High contrast stimuli are referred to as being “salient” and low contrast stimuli as “non-salient”. The background was gray (9.8 cd/m2).


Pre-stimulus activity predicts the winner of top-down vs. bottom-up attentional selection.

Mazaheri A, DiQuattro NE, Bengson J, Geng JJ - PLoS ONE (2011)

Example trial procedure.Each trial began with a blink of the fixation diamond. After a jittered interval, the visual search items appeared (illustrated here by a target in the left visual field) and subjects were free to move their eyes and indicate whether the target “t” was upright or inverted. Targets appeared alone, with a neutral distractor, or a salient distractor. Note that items are not drawn to scale for illustrative clarity.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3046127&req=5

pone-0016243-g001: Example trial procedure.Each trial began with a blink of the fixation diamond. After a jittered interval, the visual search items appeared (illustrated here by a target in the left visual field) and subjects were free to move their eyes and indicate whether the target “t” was upright or inverted. Targets appeared alone, with a neutral distractor, or a salient distractor. Note that items are not drawn to scale for illustrative clarity.
Mentions: Stimuli were composed of a ‘t’-like stimulus superimposed on a square background ( Fig. 1). Target stimuli were defined as an upright or inverted “t” and were located randomly in the left or right lower visual field (6.3° of horizontal and vertical visual angle from fixation). Targets subtended approximately .9° of visual angle at fixation. The distractor stimuli (90° rotations of target) were either low contrast (Michelson Contrast Ratio = .51; foreground luminance = 5.4 cd/m2, background luminance = 16.8 cd/m2) or high contrast (Michelson Contrast Ratio = .96; foreground luminance = .54 cd/m2, background luminance = 30.5 cd/m2); High contrast stimuli are referred to as being “salient” and low contrast stimuli as “non-salient”. The background was gray (9.8 cd/m2).

Bottom Line: Our ability to process visual information is fundamentally limited.This leads to competition between sensory information that is relevant for top-down goals and sensory information that is perceptually salient, but task-irrelevant.We propose that the high frontal alpha reflects a disengagement of attentional control whereas the transient posterior alpha time-locked to the saccade indicates sensory inhibition of the salient distractor and suppression of bottom-up oculomotor capture.

View Article: PubMed Central - PubMed

Affiliation: Center for Mind and Brain, University of California Davis, Davis, California, United States of America. a.mazaheri@donders.ru.nl

ABSTRACT
Our ability to process visual information is fundamentally limited. This leads to competition between sensory information that is relevant for top-down goals and sensory information that is perceptually salient, but task-irrelevant. The aim of the present study was to identify, from EEG recordings, pre-stimulus and pre-saccadic neural activity that could predict whether top-down or bottom-up processes would win the competition for attention on a trial-by-trial basis. We employed a visual search paradigm in which a lateralized low contrast target appeared alone, or with a low (i.e., non-salient) or high contrast (i.e., salient) distractor. Trials with a salient distractor were of primary interest due to the strong competition between top-down knowledge and bottom-up attentional capture. Our results demonstrated that 1) in the 1-sec pre-stimulus interval, frontal alpha (8-12 Hz) activity was higher on trials where the salient distractor captured attention and the first saccade (bottom-up win); and 2) there was a transient pre-saccadic increase in posterior-parietal alpha (7-8 Hz) activity on trials where the first saccade went to the target (top-down win). We propose that the high frontal alpha reflects a disengagement of attentional control whereas the transient posterior alpha time-locked to the saccade indicates sensory inhibition of the salient distractor and suppression of bottom-up oculomotor capture.

Show MeSH
Related in: MedlinePlus