Neural dynamics of the attentional blink revealed by encoding orientation selectivity during rapid visual presentation

Abstract

The human brain is inherently limited in the information it can make consciously accessible. When people monitor a rapid stream of visual items for two targets, they can typically report the first, but not the second target, if these appear within 200-500 ms of each other, a phenomenon known as the attentional blink (AB). No work has determined the neural basis for the AB, partly because conventional neuroimaging approaches lack the temporal resolution to adequately characterise the neural activity elicited by each item in a rapid stream. Here we introduce a new approach that can identify the precise effect of the AB on behaviour and neural activity. Specifically, we employed a multivariate encoding approach to extract feature-selective information carried by randomly-oriented gratings within a rapid serial stream. We show that feature selectivity is enhanced for correctly reported targets and suppressed when the same items are missed. By contrast, no such effects were apparent for irrelevant distractor items. Our findings point to a new theoretical account that involves both short- and long-range temporal interactions between visual items competing for consciousness.

Representational Dynamics Preceding Conscious Access

“…Our findings corroborate previous work showing that multiple sensory representations can coexist in patterns of neural activity for a few hundred milliseconds, presumably at different (early) stages of processing (Grootswagers et al, 2019;Marti & Dehaene, 2017;Tang et al, 2020). Temporal decoding profiles of target and distractor stimuli were robust and remarkably similar up to approximately 250 ms, confirming that early stages of visual processing are common to all stimuli -seen or unseen -entering the visual system, while late-stage processing is selective to consciously perceived stimuli (Marti & Dehaene, 2017).…”

“…Previous fMRI studies have shown enhanced T2 processing in T2-seen trials, in frontal and parietal areas as well as in low-level visual areas, such as the primary visual cortex (Hein, Alink, Kleinschmidt, & Müller, 2009;Slagter, Johnstone, Beets, & Davidson, 2010;Williams, Visser, Cunnington, & Mattingley, 2008). Using EEG, Tang et al (2020), as noted above, also observed differences in early T2 orientation representation between blink and no-blink trials, within 100-150ms post-T2. Yet, here, while we could decode T2 number identity peaking around 170 ms, we could do so equally well in T2 blink and no-blink trials.…”

“…Yet, this study unexpectedly did not find any differences in T1 or D1 representations between T2 seen and unseen trials. One notable difference between the current study and the study by Tang et al (2020) is that the latter study examined changes in the representation of a stimulus feature (orientation) that did not dissociate targets from distractors, as target and distractors were defined by spatial frequency. As we decoded features that identified targets and distractors, it is possible that we were more sensitive to picking up effects of feature attention on sensory representations of T1 and D1.…”

“…David, Hayden, Mazer, & Gallant, 2008;Fang, Becker, & Liu, 2019;Ling, Liu, & Carrasco, 2009;Williford & Maunsell, 2006). Indeed, a recent study using EEG and forward encoding modelling found that T2 selection was associated with an increase in gain, not the precision of its neural representation, suggesting that temporal attention works in a similar manner as spatial attention (Tang et al, 2020). Yet, this study unexpectedly did not find any differences in T1 or D1 representations between T2 seen and unseen trials.…”

“…However, a more recent study that compared the negativity arising after the frontal selection positivity component between two conditions that differed only in the temporal position of the first post-T1 distractor (TD and TTD) did not observe a latency shift of the frontal negativity component, challenging the assumption that the frontal negativity reflects a distractorevoked inhibitory response (Dell'Acqua et al, 2016). Furthermore, a recent study that used inverted encoding modeling to decode the orientation of each item in the AB task (stimuli were oriented gratings with different spatial frequencies), which could thus isolate single-item processing dynamics, only observed AB-related changes in early orientation tuning to T2, but no differences in the representational strength of D1 as a function of T2 visibility (Tang et al, 2020).…”