Brain potentials elicited by matching global and occluded 3-dimensional contours

The human brain deals with violating general color or depth knowledge in different time courses

Utilizing the high temporal resolution of event-related potentials (ERPs), we compared the time course of processing incongruent color versus 3D-depth information. Participants were asked to judge whether the food color (color condition) or 3D structure (3D-depth condition) was congruent or incongruent with their previous knowledge and experience. The behavioral results showed that the reaction times in the congruent 3D-depth condition were slower than those in the congruent color condition. The reaction times in the incongruent 3D-depth condition were slower than those in the incongruent color condition. The ERP results showed that incongruent color stimuli induced a larger N270, larger P300, and smaller N400 components in the fronto-central region than the congruent color stimuli. Incongruent 3D-depth stimuli induced a smaller N1 in the occipital region, larger P300 and smaller N400 in the parietal-occipital region than congruent 3D-depth stimuli. The time-frequency analysis found that incongruent color stimuli induced a larger theta band (360-580 ms) activation in the fronto-central region than congruent color stimuli. Incongruent 3D-depth stimuli induced larger alpha and beta bands (240-350 ms) activation in the parietal region than congruent 3D-depth stimuli. Our results suggest that the human brain deals with violating general color or depth knowledge in different time courses. We speculate that the depth perception conflict was dominated by solving the problem with visual processing, whereas the color perception conflict was dominated by solving the problem with semantic violation.

Neural adaptation to non-symbolic number and visual shape: an electrophysiological study

Several studies assumed that the analysis of numerical information happens in a fast and automatic manner in the human brain. Utilizing the high temporal resolution of electroencephalography (EEG) in a passive oddball adaptation paradigm, we compared event-related brain potentials (ERPs) evoked by unattended shape changes and unattended numerosity changes. We controlled visual stimulus properties in a stringent manner. Unattended changes in shape elicited significant, gradual adaptation effects in the range of early visual components, indicating the fast and automatic processing of shapes. Changes in numerosity did not elicit significant changes in these early ERP components. The lack of early number-specific effects was qualified by a significant interaction between Shape and Number conditions. Number change elicited gradual ERP effects only on late ERP components. We conclude that numerosity is a higher-level property assembled from naturally correlating perceptual cues and hence, it is identified later in the cognitive processing stream.

Visual completion processing in human face perception

Subjects discriminated whether two sequentially presented human face pictures (S1 and S2) were identical while event-related potentials were recorded to explore the neural basis of visual completion for occluded objects. Four kinds of stimulus trials were employed: S2 and S1 were identical (match-complete); S2 and S1 were identical, but S2 was partially occluded (match-incomplete); S2 was a different face from S1 (mismatch-complete); S2 was different from S1, and was partially occluded (mismatch-incomplete). Incomplete faces enhanced the amplitude of N1 compared with complete faces. The peak latency of N2 elicited by incomplete faces was delayed about 20 ms compared with complete faces. The enhancement of N1 is related to visual completion processing that requires additional time.

Various conflicts from ventral and dorsal streams are sequentially processed in a common system

Event-related potentials (ERPs) were recorded in subjects while they were matching two sequentially presented color spots. The two spots might be presented in the same position of the same color, or different colors (color conflict). They might be in different positions of the same color (position conflict), or different colors (color and position conjunction conflicts). Subjects matched the stimuli in three different sessions according to different attention tasks: attending to color, attending to position, or attending to both color and position. A negative one-peak brain potential, N270, was elicited in all the conflict conditions with amplitude enhanced in the task-relevant conflict. Two negative effects, N270 and N400, were recorded when attending to the conjunction conflicts concurrently. Visual spatial information is processed through the dorsal stream, while the feature information is processed through the ventral stream in the brain. The results suggest that all kinds of conflicts might be processed in a common system above the level of the two streams, which processes the conjunction conflict information from ventral and dorsal stream in series.

Event-related potentials elicited by visual stimulus-duration discrimination tasks

Event-related potentials (ERPs) were recorded on subjects who discriminated the stimulus duration of two sequentially presented spots (S1 and S2). Four kinds of trials were included: short-duration match (S1 and S2 lasting 300 ms), short-duration conflict (S1 and S2 lasting 300 ms and 600 ms, respectively), long-duration match (S1 and S2 were 600 ms) and long-duration conflict (S1 and S2 were 600 ms and 900 ms, respectively). When S1 was equal to S2, components of P1, N1, P2, N2 and a delayed late positive component were recorded after the onset of S2. The other three negativities were elicited in both short and long duration conflict conditions. The three negative components peaked at 475, 600 and 900 ms in the short-duration condition, and they peaked at 805, 900 and 1200 ms in the long-duration condition. The first negativity was considered a visual mis-match negativity (vMMN), followed by a delayed N270 reflecting the conflict processing for duration in the brain. The last negativity, similar to N270, possibly reflects the second conflict processing activity evoked by stimulus offset.