Abstract
Beyond attending to locations, features, and simple objects, it seems as if we can attend to visual categories, such as "cars" or "beaches". This hints that attentional tuning may extend to categorical information. We used magnetoencephalography (MEG) to investigated the neural dynamics of category-based attention. Participants (n=24) viewed rapid serial visual presentation (RSVP) streams consisting of six images (100ms each) from eight categories. Participants reported the presence or absence of a target image. On each trial, the target category was 1) cued before the RSVP [precue], 2) cued after the RSVP [postcue], or 3) not cued. Consistent with previous research (e.g. Potter & Hagman, 2015), performance was above chance for both pre- and post-cued trials, with a strong advantage for precues vs. postcues: participants were more accurate (p< 0.001) and faster (p< 0.001) to detect targets when they had seen a cue before the RSVP. This suggests that a cue to attend to a particular category facilitates its processing at some level. To determine if this facilitation occurs at the earliest stages of visual processing, we used pattern classification to measure category information across the timecourse of each trial. We used trial-by-trial amplitude in 41 occipital MEG channels as features for classification. During the RSVP, not only could we decode the category of the target (17.5% [chance=12.5%], p< 0.001), but we could also decode the category of each individual distractor image (18-20%, ps< 0.001). Of these measures, target category decoding was greater for correct than incorrect trials (p< 0.01), but target classification based on MEG signals was not influenced by the presence of a cue. Thus, early visual responses contain information about both relevant and irrelevant categories, and that the fidelity of target representation is linked to performance. However, cueing does not appear to affect categorical information in early visual processing.
Meeting abstract presented at VSS 2018