Neurophysiological indicators of internal attention: An electroencephalography-eye-tracking coregistration study

Abstract

Introduction: Many goal-directed and spontaneous everyday activities (e.g., planning, mind wandering) rely on an internal focus of attention. Internally directed cognition (IDC) was shown to differ from externally directed cognition in a range of neurophysiological indicators such as electroencephalogram (EEG) alpha activity and eye behavior.

Methods: In this EEG-eye-tracking coregistration study, we investigated effects of attention direction on EEG alpha activity and various relevant eye parameters. We used an established paradigm to manipulate internal attention demands in the visual domain within tasks by means of conditional stimulus masking.

Results: Consistent with previous research, IDC involved relatively higher EEG alpha activity (lower alpha desynchronization) at posterior cortical sites. Moreover, IDC was characterized by greater pupil diameter (PD), fewer microsaccades, fixations, and saccades. These findings show that internal versus external cognition is associated with robust differences in several indicators at the neural and perceptual level. In a second line of analysis, we explored the intrinsic temporal covariation between EEG alpha activity and eye parameters during rest. This analysis revealed a positive correlation of EEG alpha power with PD especially in bilateral parieto-occipital regions.

Conclusion: Together, these findings suggest that EEG alpha activity and PD represent time-sensitive indicators of internal attention demands, which may be involved in a neurophysiological gating mechanism serving to shield internal cognition from irrelevant sensory information.

Keywords: divergent thinking; electroencephalography; eye tracking; internal attention.

Figure 1

Exemplary segmented data of the 120 s resting state period of one participant, which forms the basis of the electroencephalography (EEG)—eye‐tracking covariation analysis. All EEG and eye‐tracking parameters were segmented to 1‐s segments represented by single tiles. Continuous parameters (EEG alpha, and PD, PD variance, AoEV, and AoEV variance) were z‐scaled; for discrete parameters, the frequency of occurrence within the time segment was counted. AF, anteriofrontal; AoEV, Angle of Eye Vergence; CT, centro‐temporal; F = frontal; O, occipital; P, parietal; PD, pupil diameter. Gray tiles mark missing data

Figure 2

Task‐related power (TRP) changes in the alpha band (8.5–12.5 Hz) during anagram generation (AN) and sentence generation (SG) for experimental conditions of externally directed cognition (EDC) versus internally directed cognition (IDC). Positive TRP (cool colors) indicates task‐related alpha synchronization, and negative TRP (warm colors) indicates desynchronization (AF, anteriofrontal; CT, centro‐temporal; F = frontal; P, parietal; O, occipital). IDC resulted in relatively higher TRP in posterior brain regions for both tasks

Figure 3

Effect sizes of oculometric differences between internally directed cognition (IDC) and externally directed cognition (EDC). AoEV, angle of eye vergence; PD, pupil diameter. ***p < .001, **p < .01

Figure 4

Correlations between electroencephalography (EEG) alpha power and eye parameters during the 120 s rest period (left). Bold numbers denote significant average correlations (p < .00125). Topographical plot of correlations between pupil diameter (PD) and EEG alpha power for aggregated channels (right). Violet tones denote positive correlations, and orange tones denote negative correlations. AoEV, angle of eye vergence; MS, microsaccade; var., variance