The loci of oscillatory visual-object priming: a combined electroencephalographic and reaction-time study

The detection of reaction-times (RTs) to a target Kanizsa-type square (an i llusory square defined by the collinear arrangement of 90 degrees corner ju nctions) within a matrix of distracter junctions are expedited when the tar get display is preceded by a 40-Hz flickering display of premask crosses pr esented prior to, and at the locations subsequently occupied by the junctio ns of the target display. Priming effects were obtained when four crosses ( which together matched the Gestalt arrangement of the target) were presente d at the display locations subsequently occupied by the junctions forming t he target Kanizsa square (Elliott and Muller, 1998; Elliott and Muller, 200 0). The present study was conducted with the aim of replicating the 40-Hz R T priming effects, while simultaneously recording the observers EEG in orde r to establish the presence and location of Gestalt priming in the brain. T he statistical pattern obtained in the RT data corresponded well with previ ous studies and was matched by the pattern of target P300 latencies across bilateral central and posterior electrodes. Planned analyses focused upon t he evoked 40-Hz activity that co-occurs with the P300, revealing a more spe cific pattern of 40-Hz priming over the visual cortex. A subsequent series of cross-correlational analyses examined the cortical distribution and timi ng of Gestalt-prime generation during and subsequent to premask-display pre sentation. Correlations were revealed between stimulus related 40-Hz activi ty over a range of cortical loci, including the right temporal lobe, which is considered important for figure coding. Taken together, these findings n ot only support the role of a distributed 40-Hz mechanism during Gestalt-fi gure priming, but also suggest that patterns of oscillatory brain activity may be directly influenced by, and interpretable in terms of equivalent tem poral patterns of stimulus activity. (C) 2000 Elsevier Science B.V. All rig hts reserved.