Abstract
Schizophrenia is associated with deficits in both object perception and visual attention. However, few studies in schizophrenia have investigated object-based attention, which is dissociable from other forms of visuospatial attention. Recent research in healthy populations has shown that the ‘spotlight’ of sustained visual attention flickers in a rhythmic, oscillatory fashion at specific frequencies in the 4-12Hz range. In healthy samples, this oscillatory signature has been used to investigate spatiotemporal dynamics of object-based attention, showing that the attentional spotlight spreads to uncued locations within cued objects, and also periodically alternates focus between cued and uncued objects. In this study, we adapted a performance-based visual object cueing task to investigate object-based attention in schizophrenia and matched healthy controls. In controls, spatiotemporal patterns of object-based attention closely resembled those reported in previous studies of healthy individuals. Members of the schizophrenia group also showed the oscillatory signature of attention at low frequencies in the location of the cue and on uncued objects, similar to controls. Indeed, the oscillatory signature of attention at the spatial location of the cue was stronger in the schizophrenia group than in controls. However, there was no indication of attention spreading across the cued object in schizophrenia; rather, attention appeared to remain hyperfocused at the spatial location of the cue. These findings provide the first evidence that visual attention has oscillatory characteristics in schizophrenia, as in the general population. However, the results also demonstrate that the fundamental process of attentional spreading which underlies object-based attention is abnormal in schizophrenia.