Neural competition for conscious representation across time: an fMRI study

Abstract

Background: The information processing capacity of the human mind is limited, as is evidenced by the attentional blink (AB)--a deficit in identifying the second of two temporally-close targets (T1 and T2) embedded in a rapid stream of distracters. Theories of the AB generally agree that it results from competition between stimuli for conscious representation. However, they disagree in the specific mechanisms, in particular about how attentional processing of T1 determines the AB to T2.

Methodology/principal findings: The present study used the high spatial resolution of functional magnetic resonance imaging (fMRI) to examine the neural mechanisms underlying the AB. Our research approach was to design T1 and T2 stimuli that activate distinguishable brain areas involved in visual categorization and representation. ROI and functional connectivity analyses were then used to examine how attentional processing of T1, as indexed by activity in the T1 representation area, affected T2 processing. Our main finding was that attentional processing of T1 at the level of the visual cortex predicted T2 detection rates Those individuals who activated the T1 encoding area more strongly in blink versus no-blink trials generally detected T2 on a lower percentage of trials. The coupling of activity between T1 and T2 representation areas did not vary as a function of conscious T2 perception.

Conclusions/significance: These data are consistent with the notion that the AB is related to attentional demands of T1 for selection, and indicate that these demands are reflected at the level of visual cortex. They also highlight the importance of individual differences in attentional settings in explaining AB task performance.

Figure 1. The attentional blink task.

Example of a trial.

Figure 2. Behavioral T2 performance.

A: Data from the behavioral pilot experiment. T2 accuracy as a function of Lag (200, 400, 600 or 800 ms) and Task Condition (single, dual). B: Behavioral data collected in the MRI scanner. T2 accuracy as a function of Lag (short, long).

Figure 3. Brain regions associated with conscious T2 perception (A) and body parts and natural scenes (B).

A: Frontoparietal network associated with conscious T2 perception (p<0.05 after controlling for False Discovery Rate). LPFC, lateral prefrontal cortex; SMFC, superior medial frontal cortex; PCG, precentral gyrus; IPS, intraparietal sulcus; PPA, parahippocampal place area; STRI, striatum. B: Localizer task data. The ‘representative subject’ map shows the 8 most active contiguous voxels for each region of interest (p<.0001). The ‘group data’ map is thresholded at q<.05 (or p<.0006).

Figure 4. The relationship between individual differences in prefrontal brain activity and T2 accuracy.

Greater activity in left posterior lateral prefrontal cortex selectively predicted higher T2 detection rates.

Figure 5. T1- and T2-object specific activity during the localizer task (A) and the AB task (B).

A: Selective activity in the EBA and PPA during the localizer task to bodies and scenes, respectively. B: Activity in the EBA and PPA during the AB task as a function of conscious T2 perception (blink, no-blink). While the EBA was equally active in no-blink and blink trials, the PPA exhibited significantly greater activation when T2 was consciously perceived.

Figure 6. T1-related EBA activity predicts T2 accuracy across participants.