Neuroelectric Correlates of Perceptual Awareness During the Auditory Attentional Blink

Abstract

Background: Perceptual awareness refers to the conscious detection and identification of a sensory event. In electrophysiological studies, it is associated with a modality-specific negative-going event-related potential, which can be observed as early as 100-300 ms after the stimulus onset.

Method: In this study, we measured neuroelectric brain activity during the auditory attentional blink, comparing brain responses when participants correctly reported both the first (T1) and second (T2) targets versus when only T1 was detected, but T2 was missed. To achieve robust statistical power, we pooled data across six previously published studies for the current analyses.

Result: Our results revealed that accurately reporting both T1 and T2 elicited greater negativity between 150 and 300 ms over the frontocentral and central scalp areas following T2 onset, compared to trials where T1 was detected but T2 was not. Additionally, a positive displacement, peaking around 800 ms over the central-parietal scalp area, followed the early negativity. Successful detection of both T1 and T2 was also associated with more pronounced alpha suppression, peaking at approximately 500 ms before and 800 ms after T2 onset.

Conclusions: These findings suggest that neural correlates of what we refer to "auditory awareness" occur both before the stimulus sequence and soon after T2 onset. Pre-stimulus difference in alpha power may serve as an indicator of lapses in attention, with greater alpha power reflecting periods when participants are less engaged or off-task.

Keywords: EEG; ERP; attentional blink; auditory; awareness-related negativity.

Figure 1

Schematic of a single trial in a typical attentional blink paradigm. Each trial began with a fixation cross displayed on a computer screen, followed by a sequence of 16 auditory stimuli. In the illustrated example, the first auditory target (T1) occurs at the 5th position, with the second target (T2) occurring two positions later. Distractors (D) are non-target stimuli interspersed throughout the sequence. R1 and R2 represent responses to T1 and T2, respectively. The stimulus onset asynchrony (SOA) denotes the time interval between the onsets of any two stimuli.

Figure 2

Brain responses elicited when the first (T1) and second (T2) targets were correctly detected (Hits) versus when only T1 was detected (Misses). (a) Group mean event-related potential time-locked on T2 onset (0 ms) at the midline central parietal electrode (CPz) for hits and misses. The color shaded areas show the group mean standard deviation. The gray shaded areas show the interval where the amplitude difference was significant. (b) Iso-contour maps for the difference in ERP amplitude between hits and misses. The contour maps show the mean amplitude for the early (216–256 ms) and late (780–820 ms) modulations following T2 onset.

Figure 3

Brain electrical source analysis. Distributed source analysis of group mean difference wave using an iterative application of Low-Resolution Electromagnetic Tomography (LORETA) termed Classical LORETA Analysis Recursively Applied (CLARA). The top panel shows the mean source activity for the 216–256 interval, whereas the bottom panel shows the solution for the 780–820 ms interval.

Figure 4

Time–frequency analysis. (a) Alpha power (% change relative to baseline −1000 to −800 ms) before and after the onset of the secondary target. Time–frequency for hits (left panel) and misses (right panel) from the right central electrode (C4). The dashed box highlights the intervals of differences in alpha power (8–12 Hz). Alpha synchronization was higher for the misses. (b) Contour map of pre-stimulus mean alpha power for the −550 to −450 ms interval for hits and misses.