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

Summary

Attention control comprises enhancement of target signals and attenuation of distractor signals. We describe an approach to measure separately but concurrently, the neurophysiology of attending and ignoring in sustained intermodal attention, utilizing a passive control condition during which neither process is continuously engaged.

Abstract

Attention control is the ability to selectively attend to some sensory signals while ignoring others. This ability is thought to involve two processes: enhancement of sensory signals that are to be attended and the attenuation of sensory signals that are to be ignored. The overall strength of attentional modulation is often measured by comparing the amplitude of a sensory neural response to an external input when attended versus when ignored. This method is robust for detecting attentional modulation, but precludes the ability to assess the separate dynamics of attending and ignoring processes. Here, we describe methodology to measure independently the neurophysiological signals of attending and ignoring using the intermodal attention task (IMAT). This task, when combined with electroencephalography, isolates neurophysiological sensory responses in auditory and visual modalities, when either attending or ignoring, with respect to a passive control. As a result, independent dynamics of attending and of a ignoring can be assessed in either modality. Our results using this task indicate that the timing and cortical sources of attending and ignoring effects differ, as do their contributions to the attention modulation effect, pointing to unique neural trajectories and demonstrating sample utility of measuring them separately.

Introduction

Attention control guides behavior by directing our neural and cognitive resources toward select input signals, while restricting access to other signals, based on a given behavioral goal ¹. For instance, when reading a book, the visual signals corresponding to the book are the target signals to be enhanced, whereas other sensory signals — such as the TV in the next room — are distractor signals to be attenuated. Recordings in both human and non-human primates ^1-4, indicate that neural responses in sensory cortices are enhanced for attended targets relative to ignored distractors during selective attention, indicating that the strength....

Protocol

NOTE: This study protocol was developed in accordance with the ethical guidelines approved by the investigational review board at University of California Los Angles.

1. Preparation of Auditory and Visual Stimuli

1. Using software in which visual images can be generated, create two gray scale sinusoid gratings, approximately 5.7 inches in diameter and of any frequency (e.g., 1.36 cycles/degree of visual angle). The images will have an on-screen duration of 100 msec.
   1. Tilt one of the gratings about 10 visual degrees to the right off the median, and tilt the other grating the same amount to the left of the grating....

Results

The IMAT protocol has been used previously to identify the unique contributions of attending and ignoring processes to response speed during sustained attention ¹⁸. In that study, we tested 35 healthy right-handed individuals (22 female, age: x̅ = 21.0, σ = 5.4), recruited through the Psychology department subject pool at the University of California, Los Angeles. All participants provided written informed consent prior to participating in the study. Representative results highlight the value of measuring atte.......

Discussion

Processes related to attending and to ignoring in attention control may involve different neural pathways and time courses. Therefore, it is of value to measure these processes separately. The IMAT is a tool, by which one may capture neurophysiological signals of attending and ignoring separately, but concurrently, in sustained attention. The critical steps include the measurement of sensory neurophysiological responses when the participant is attending, ignoring or passively perceiving stimuli presented in a given modal.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
NetStation Software	Electrical Geodesic, Inc.	version 4.5.1	Alternate recording software may be used.
Matlab Software	The MathWorks, Inc.	7.10.0 (R2010a)	Alternate analysis and presentation software may be used.
PsychToolbox Software	http://psychtoolbox.org/	v3.0.8 (2010-03-06)	Open-source software. Alternate stimulus presentation software may be used.
Netstation Amplifier	Electrical Geodesic, Inc.	300	Alternate amplifier may be used.
EEG Net	Electrical Geodesic, Inc.	HCGSN130	Alternate EEG cap may be used.
Saline-Based Electrolyte (Potassium Chloride)	Electrical Geodesic, Inc.	n/a	Electrolyte used in soaking of net for this high-impedance EEG system. Alternate electrolyte mediate can be used.