Takashi Morotomi

Face-specific N170 component is modulated by facial expressional change.

We examined processing of change in facial expression. Event-related brain potentials (ERPs) were elicited by successive presentation of two different faces without interval. Smile faces were preceded by either a neutral face of the same person, a smile face of a different person, or a neutral face of a different person, which generated expressional, individual, or both expressional and individual change, respectively. For the preceding faces, there were no differences in face-specific N170. In contrast, the second faces elicited a larger N170 for expressional change relative to individual or both changes, which indicates that facial expression was processed in the early stage of face processing in the posterior temporal region, when they are presented in change context.

Attending to a location in three-dimensional space modulates early ERPs

It has been reported that attending to a particular location can modulate incoming sensory signals, as reflected by the stimulus-evoked P1 and N1 components of the visual event-related potential (ERPs) in a two-dimensional (2D) display [Attention, Space, and Action: Studies in Cognitive Neuroscience, Oxford University Press, New York, 1999, p. 31]. In contrast, in this study we examined the effect of attention in 3D space using a stereoscopic display. Stimuli were presented randomly, one at a time, in an orthogonal combination of two depths (near, far) and two 2D locations (left, right) relative to the fixation point. The task was to attend selectively to one of these four positions and to respond to a target stimulus defined by shape in the attended 3D location. The effect of 2D location selection on the P1 amplitude was greater for stimuli in the near than the far depth plane, and the amplitude of N1 increased in response to stimuli in the attended combination of 2D location and depth. These results suggest that the effect of early spatial selection on the visual ERP is not simply based on retinotopic organization of the visual field, but also on intermediate stages that construct a 3D spatial representation of the external world.

Integrated neural representation of sound and temporal features in human auditory sensory memory: an event-related potential study

The present study explored the effect of varying stimulus onset asynchrony (SOA) on the pre-attentive detection of frequency changes indexed by the mismatch negativity (MMN). Reading subjects were presented with sequences of tones delivered at two SOAs. Each sequence included either one or both of the two SOAs. In sequences with two SOAs, the order of the SOAs was alternated or sequenced randomly. The MMN amplitude was larger in sequences with one SOA than in those with two. The order of SOAs (alternate or random) had no effect on the MMN. These results revealed that the processings of frequency and SOA are not independent, suggesting that sound features and the timing of stimulation delivering the sound can be encoded into a functionally integrated representation.

Event-related brain potentials during selective attention to depth and form in global stereopsis

To elucidate the discriminating processes of surface depth and boundary form in global stereopsis, event-related brain potentials (ERPs) were investigated by the detection of combinations of the attributes in random sequences. The attentional relevance of depth or form was associated with selection negativities (SNs) over the lateral occipito-temporal regions initiating at about 200 ms post-stimulus. The initial SNs were elicited irrespective of relevance to the other feature; the following parts increased only for stimuli with crossed disparity having the relevant dimension of the other feature, suggesting the independent selection of stereoscopic depth and form followed by the perceptual integration into an object.

Enhancement of averaged evoked responses to brief flashes after offset of preexposed light stimulation: A critical moment

Abstract Dim test flash disks (TFs) of 20 /gmsec duration, below 0.001 mL, were exposed after termination of preexposed conditioning light disks (CLs) of 3 sec duration, 0.003 mL, with CL-TF intervals ranging from 100 to 1000 msec. Major finding was that the critical momentwas the brief period between 250 and 500 msec after the CL offset when the amplitude enhancementof the visual evoked potential(VEP) to the TF occurred to the greatest extent. The result suggested that there is the facilitatory process in the visual system a short time after termination of preceding light stimulation.

Enhancement of evoked responses to brief flashes and its correlation with off responses to pre-exposed light stimulation.

Abstract The offset evoked potentials (EPs) to the termination of conditioning lights (CLs) and the onset EPs to test flashes (TFs) with a duration of 20 μsec, exposed 300 msec after the CL cessation, were analyzed as to the CL duration ranging from 20 μsec to 9 sec. The amplitude of the offset EP, and that of the EP to the TF became larger as the CL duration was made longer. Remarkable enhancement of the EP amplitude to the TF was found if the CL lasted a longer time.

Color-specific filtering of rival binocular inputs induced by priming1

:  In a situation where the two eyes separately receive two dissimilar images such as a blue square and a red square, the brain is forced to resolve competitive interpretations of the visual inputs. Earlier studies have indicated that adaptation to one of two rival images can control the following competitive perception. Consistent with those studies, the present experiments revealed that immediately after a brief presentation of a color (priming stimulation) to the two eyes, subjects dominantly perceived the other color out of the chromatic rivalry. This effect showed an interocular transfer even if indirect monocular priming was employed, but the filtering out of a primed color did not occur when an unprimed rival image was removed from the other eye. These facts suggest that binocular feature-detection processes in the human visual system might be responsible for the priming effect on rival images.

1-A-D-17. The influence of spatial frequency and autistic traits on the perception of change in facial expression: An event-related potential study

We studied visual information process of dynamic facial expressions in autism spectrum condition. Our aim was to investigate how P1 and N170 ERP components are affected by an interaction with the spatial frequencies and autistic traits. We filtered low spatial frequency information or high spatial frequency information from grayscale face pictures. These face stimuli consisted of neutral, happy and angry expressions. Sixteen healthy participants observed the change in facial expression (Miyoshi et al., 2004). They were assessed autistic traits by Autism-Spectrum Quotient Japanese version (AQ, Baron-Cohen et al., 2001; Wakabayashi et al., 2004). When participants viewed the change in low spatial frequency facial expression, P1 amplitude from parieto-occipital electrode was attenuated in participants with high AQ group. In the high spatial frequency condition, participants with greater autistic trait showed more smaller N170 amplitude to the change in facial expression at the posterior temporal site. Our findings suggest that individuals with high autistic traits may have aberrant visual processing of spatial frequency information.