Surprise? Early visual novelty processing is not modulated by attention

Abstract

This study investigated the influence of direction of attention on the early detection of visual novelty, as indexed by the anterior N2. The anterior N2 was measured in young subjects (n=32) under an attend and an ignore condition. Subjects were presented standard, target/rare, and perceptually novel visual stimuli under both conditions, but under the ignore condition, attention was directed toward an auditory n-back task. The size of the anterior N2 to novel stimuli did not differ between conditions and was significantly larger than the anterior N2 to all other stimulus types. Furthermore, under the ignore condition, the anterior N2 to visual novel stimuli was not affected by the level of difficulty of the auditory n-back task (3-back vs. 2-back). Our findings suggest that the early processing of visual novelty, as measured by the size of the anterior N2, is not strongly modulated by direction of attention.

Figure 1

Midline grand average ERPs at frontocentral sites (Fz, FCz, Cz, Pz) in response to novel, target/rare, and standard stimuli under the A) Attend condition and the B) Ignore condition. In (A) arrows illustrate the N1, P2, N2, and P3a waves at Fz, and the P3b wave at Pz under the Attend condition. In (B) arrows illustrate the N1, P2, N2, and P3a waves at Fz.

Figure 2

Midline grand average ERPs at frontocentral sites (Fz, FCz, Cz) in response to novel stimuli under the Attend vs. Ignore conditions.

Figure 3

Midline grand average ERPs at frontocentral sites (Fz, FCz, Cz) in response to novel visual stimuli under the Ignore condition when subjects focused on the 2-back task vs. 3-back task in the auditory modality.