Phasic alerting facilitates endogenous orienting of spatial attention: Evidence from event-related lateralizations of the EEG

Asanowicz, Dariusz; Panek, Bartłomiej · 2020 · Crossref

DOI: 10.3758/s13414-019-01958-3

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Summary

This study investigates the neural mechanisms underlying the interaction between phasic alerting and endogenous spatial orienting of attention. While alerting (readiness to respond) and orienting (shifting attention to a location) are often considered independent, previous behavioral research suggests they interact, with alerting facilitating orienting. Two competing hypotheses exist: the "accelerating hypothesis," which posits that alerting speeds up the orienting process without changing its magnitude, and the "enhancing hypothesis," which suggests alerting increases the magnitude of the orienting effect without altering its time course. Asanowicz and Panek aimed to distinguish between these mechanisms by examining the temporal dynamics of event-related lateralizations (ERLs) in the electroencephalogram (EEG). The researchers employed a spatial cueing task with 43 participants. Targets were preceded by valid or neutral central cues. Phasic alerting was induced by presenting an accessory tone 100 ms or 500 ms before the cue. The 100 ms interval was selected to capture phasic alerting effects, while the 500 ms interval served as a control to prevent confounding with temporal orienting. EEG data were recorded, and ERLs were calculated by subtracting ipsilateral from contralateral activity relative to the cued location, isolating spatially specific preparatory attention shifts. The analysis focused on two key orienting-related components: the early directing attention negativity (EDAN) and the late directing attention positivity (LDAP), which reflects preparatory modulations in the ventral visual stream. Behavioral results confirmed that phasic alerting facilitated spatial orienting; the benefit of valid cueing on response times was significantly larger in the alerting condition (35 ms) compared to the no-alerting condition (24 ms). EEG analysis revealed that the alerting tone affected both the latency and amplitude of orienting-related ERLs. Specifically, the LDAP component exhibited a significantly shorter onset latency (approximately 37 ms earlier) and a larger amplitude in the alerting condition compared to the no-alerting condition. The EDAN component also showed a trend toward earlier peak latency and reduced amplitude under alerting. These effects were specific to the 100 ms tone-cue interval, supporting the isolation of phasic alerting mechanisms. The findings indicate that phasic alerting facilitates endogenous orienting by both accelerating and enhancing the preparatory neural processes associated with spatial attention. Because the alerting condition produced both faster onset and greater amplitude of the LDAP component, the results support a combined mechanism rather than exclusively one hypothesis. This suggests that alerting optimizes the ventral visual stream for upcoming stimuli by speeding up the initiation of attentional shifts and increasing the strength of the preparatory attentional modulation. The study provides neural evidence clarifying the functional interaction between alerting and orienting systems.

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• attention selective divided