Neurophysiological Signals of Ignoring and Attending Are Separable and Related to Performance during Sustained Intersensory Attention

Abstract

The ability to attend to an input selectively while ignoring distracting sensations is thought to depend on the coordination of two processes: enhancement of target signals and attenuation of distractor signals. This implies that attending and ignoring may be dissociable neural processes and that they make separable contributions to behavioral outcomes of attention. In this study, we tested these hypotheses in the context of sustained attention by measuring neurophysiological responses to attended and ignored stimuli in a noncued, continuous, audiovisual selective attention task. We compared these against responses during a passive control to quantify effects of attending and ignoring separately. In both sensory modalities, responses to ignored stimuli were attenuated relative to a passive control, whereas responses to attended stimuli were enhanced. The scalp topographies and brain activations of these modulatory effects were consistent with the sensory regions that process each modality. They also included parietal and prefrontal activations that suggest these effects arise from interactions between top–down and sensory cortices. Most importantly, we found that both attending and ignoring processes contributed to task accuracy and that these effects were not correlated—suggesting unique neural trajectories. This conclusion was supported by the novel observation that attending and ignoring differed in timing and in active cortical regions. The data provide direct evidence for the separable contributions of attending and ignoring to behavioral outcomes of attention control during sustained intersensory attention.

Measurement of Neurophysiological Signals of Ignoring and Attending Processes in Attention Control

“…This will ensure comparable difficulty between the modalities. In the presented experiment 18 , accuracy on the attend auditory task ( ̅ x = 0.94, σ = 0.01) was not significantly different than that on the attend visual task ( ̅ x = 0.93, σ = 0.01), t(34) <1, p >0.05.…”

“…The IMAT protocol has been used previously to identify the unique contributions of attending and ignoring processes to response speed during sustained attention 18 .…”

“…However, the temporal profiles of these processes depend on the choice of spatial sensors selected for analysis. In Figures 1 and 2, these were evaluated for a cluster of frontocentral and occipital electrodes, respectively 18 . At a different cluster, the temporal patterns of responses may differ.…”

“…We present here the results of such an analysis, which illustrates further information gain from the IMAT. The methods for cortical projection of EEG data is fully described elsewhere 18,24 . The cortical projections of pair-wise difference waves across the cortex (sPL: superior parietal lobe, latOcc: lateral occipital cortex, sTP: superior temporal plane), at 70 msec following stimulus onset across attend (A), ignore (I) and passive (P) conditions.…”

“…Here we describe the use of this approach in the context of sustained attention, in a non-cued, continuous, intermodal (i.e., auditory-visual) attention task (IMAT) 18 . In other words, this method is appropriate to the study of ongoing rather than preparatory control processes, allowing for tracking of these processes across time.…”