TRANSIENT ATTENTIONAL ENHANCEMENT DURING THE ATTENTIONAL BLINK: EEG CORRELATES OF THE ST2 MODEL

Abstract

The Attentional Blink (AB) is a well studied temporal attention phenomenon, and is particularly suitable for investigating the nature and limits of conscious perception. The AB employs Rapid Serial Visual Presentation (RSVP), in which a sequence of items is presented at the same spatial location at a rate of around 10 items per second, with each item rapidly replacing the previous one. At such speeds, the items presented, some of which are targets to be detected and others are irrelevant distractors, yield only fleeting mental representations, resulting in targets often being missed. In the AB, detection of a second target (T2) following a correctly identified first target (T1) is significantly impaired if T2 follows T1 within 200-600 ms. There has been considerable recent interest in the identification of neural correlates of the AB, and the development of neurally explicit explanations of it, a prominent one being the Simultaneous Type Serial Token (ST 2 ) [1] neural model. In addition to incorporating computationally explicit accounts of visual processing, item identification, attentional selection and working memory encoding, the model proposes the episodic distinctiveness hypothesis, i.e., that the AB reflects a system attempting to allocate unique episodic contexts to targets. Importantly, it suggests that when the visual system detects an item that may be task relevant, a spatially specific Transient Attentional Enhancement (TAE), called the ‘blaster’ is triggered. For a fleeting stimulus such as that arising in RSVP, the contribution of this enhancement is critical in enabling the stimulus to be encoded into working memory. This paper reports on our investigations into EEG activity during the AB, and a hypothesized correlation between the blaster and the N2pc ERP component [2]. The N2pc describes a negative deflection of the ERP at around 190-300 ms after the presentation of a laterally offset target, and is most strongly visible at posterior electrodes contralateral to the position of the target. Previous research has associated the N2pc with the selection of a target in the presence of competing distractors. We discuss findings that, in the context of the AB, suggest a correspondence between blaster activity and manifestation of the N2pc. Specifically, we demonstrate that the temporal firing pattern of the blaster in the model matches the N2pc component in human ERP recordings, for T1s and T2s that are seen and missed during the AB. Such a correlation between a computational account of the AB and ERP data provides useful insights into the processes underlying selectivity in temporal attention.