It has been proposed that the most fundamental units of attentional selection are "objects" that are grouped according to Gestalt factors such as similarity or connectedness.Previous studies using event-related potentials (ERPs) have shown that object-based attention is associated with modulations of the visual-evoked N1 component, which reflects an early cortical mechanism that is shared with spatial attention. However, these studies only examined the case of perceptually continuous objects. The present study examined the case of separate objects that are grouped according to feature similarity (color, shape), by indexing lateralized potentials at posterior sites in a sustained-attention task that involved bilateral stimulus arrays. A behavioral object effect was found only for task-relevant shape similarity. Electrophysiological results indicated that attention was guided to the task-irrelevant side of the visual field due to achromatic-color similarity in N1 (155-205 ms post-stimulus) and early N2 (210-260 ms) and due to shape similarity in early N2 and late N2 (280-400 ms) latency ranges. These results are discussed in terms of selection mechanisms and object/group representations.

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The appearance of electroencephalogram (EEG) alpha activity in a multiple sleep latency test was quantitatively analysed using percentage time alpha. Two components were extracted from the temporal change in smoothed percentage time alpha: a general level showing a progressive decrease and a cyclic variation with a mean interval of 39.8 s. The cyclic variation of percentage time alpha was evident during the period of the general level below 50%. The arousal cycle in the drowsy state is discussed.

This study investigated the semantic processing of children with autism spectrum disorder (ASD). Eventrelated potentials (ERP) with children performing silent reading tasks were analyzed. Furthermore, we used descriptive tests to require participants to answer whether a sentence was correct and to correctly rewrite the incorrect sentences. According to an analysis of ERP, the ASD group demonstrated significantly smaller N400 amplitudes compared with the typically developing (TD) group. However, no significant differences between the groups were observed in the percentage of correct answers on descriptive tests. These results suggest that children with ASD have a peculiarity of neural processing for semantically incongruent words, although they can determine whether sentences are correct or incorrect, which is similar to the TD children.