Different roles of the parietal and lateral occipito-temporal cortex for 3D perception from motion

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Abstracts / Neuroscience Research 58S (2007) S1–S244

P3-e45 Determining factors for endogenous saccadic eye movement during visual search in complex scene Noriko Katsumata 1,2 , Michel Vidal-Naquet 1 , Manabu Tanifuji 1 1 RIKEN Brain Science Institute, Japan; 2 Department of Neurosurgery, Graduate School of Tokyo Medical and Dental University, Japan It is known that when we search for a target object in a complex scene, we tend to make saccades to the visual features that stand out from the background (exogenous saccades). However, it seems less likely that we find the target object solely based on exogenous saccades during visual search. To investigate additional factors (endogenous components) involved in the saccades, we asked human subjects to perform visual search tasks in which a target object was chosen from one of three object categories that were familiarized to the subject beforehand. We then calculated the category specific information content of each local feature, centered on the saccade end-points. We found that the end points of saccades tend to provide more information about the category of the target object than randomly selected features. Thus, a determining factor for saccades during visual search could be visual features specific to the target object category.

 1 Different roles of the parietal and lateral occipitoP3-f0 temporal cortex for 3D perception from motion Tetsuya Yamamoto 1,2 , Shigeko Takahashi 3 , Takashi Hanakawa 4,5 , Shin-Ichi Urayama 4 , Toshihiko Aso 4 , Hidenao Fukuyama 4 , Yoshimichi Ejima 6 1 Grad. Schl. of Hum. & Environ. Stud., Kyoto University, Kyoto, Japan; 2 JSPS, Tokyo, Japan; 3 Fac. of Fine Arts, Kyoto Cty. University of Arts, Kyoto, Japan; 4 HBRC, Grad. Schl. of Med., Kyoto University, Kyoto, Japan; 5 Department of Cortical Funct. Disord., Natl. Inst. of Neurosci., NCNP, Kodaira, Japan; 6 Kyoto Inst. of Technol., Kyoto, Japan We can perceive a 3D object when a special figure rotates in the frontal plane about the visual axis, which is termed the stereokinetic effect (SKE). To reveal the roles of visual areas along the dorsal pathway for SKE, we compared fMRI activity in the lateral occipito-temporal (LOT) region with that in the dorsal intraparietal (DIP) region, while subjects viewed a variety of SKE stimuli or performed a spatial attention task. DIP was activated only for the class of SKE stimuli that evoked a spatial attention shift, whereas LOT did not show such preference. This suggests that LOT plays a central role in constructing 3D structures from motion, while DIP is involved in spatial attention to constructed objects. Research funds: JSPS 17-2093

P3-e46 Perceptional orientation-dependent interaction bet-

 3 Receptive field structures of transcallosally connected P3-f0

ween color and luminance

neurons in the cat’s visual cortex

Akitoshi Hanazawa LSSE, Kyushu Institute of Technology, Kitakyushu, Japan

Yusuke Asada, Takahisa M. Sanada, Izumi Ohzawa Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan

Isoluminant color modulation such as a red–green color grating perceptually fades by gaze fixation when presented on uniform background (Troxler fading) or superimposed on a orthogonal luminance grating (monocular rivalry). In this study, we found that a moving luminance grating enhances the perceptual fading of the color grating when superimposed orthogonally, and abolishes the fading when superimposed parallel. Perception of a static color grating was suppressed by superimposing a moving orthogonal luminance grating. When the color grating was moving, Troxler fading and monocular rivalry did not occur. The moving luminance grating, however, suppressed the perception of the moving color grating. When the orientation of the luminance grating was the same as that of the color grating, the perceptual suppression never occurred even when the luminance grating was smaller than the color grating. These results suggest that there are enhancing and suppressive perceptual interactions between color and luminance when their orientations are the same and orthogonal, respectively.

How are receptive fields organized for transcallosally connected visual neurons? Although previous studies showed that hand-plotted receptive field of interhemispheric synchronized neurons are typically overlapped and their orientation preferences are similar, structures of the receptive fields were not clarified. To investigate the spatial organizations of receptive-fields these neurons, a reverse correlation analysis is used. Simultaneous recordings were made in left and right hemispheres from the border areas between area 17 and 18 (transitional zone). Interhemispheric connectivity was examined by cross-correlation analysis. Contrary to previous studies, however, we found that some pairs of connected neurons have different orientation preference. In addition, subregions of the paired neurons show various response polarities, where the overlaps were observed not only for ON–ON or OFF–OFF, but also for ON–OFF combinations. These results suggest greater complexity in the pattern of callosal connectivity than that previously thought. Research funds: MEXT(18020017), JSPS(13308048), COE21

P3-e47 Functional maps of visual responses with a multipleelectrode array in macaque inferotemporal cortex Manabu Tanifuji 1 , Naohisa Miyakawa 1 , David Blake 2 , Micheal Merzenich 1,2 1 The Synapses & Cog. Neurosci. Center, Medical College of Georgia, United States; 2 Keck Center for Integrative Neurosci., UCSF, United States Previous studies with intrinsic signal imaging revealed that an object image is represented by a combination of columns each representing visual features. To address a question how object recognition relates to object representation with multiple columns, it is essential to investigate spatiotemporal patterns of activity maps with monkeys working on visual recognition tasks. Intrinsic signal imaging, however, is not appropriate for this purpose because the signals are indirect measures of neural activities and because of their low S/N ratio. In this study, we developed a densely arranged multiple electrode array that is available in behaving monkeys and have spatial resolution roughly comparable to intrinsic signal imaging. The array consisted of 16 (4 × 4) or 49 (7 × 7) electrodes (spacing, 350 ␮m) which were arranged to cover 1.05 mm × 1.05 mm or 2.1 mm × 2.1 mm area along the cortical surface. With this array, we successfully reconstructed a two-dimensional functional map elicited by object stimuli.

 4 Characteristics of surround modulation and stimulus P3-f0 shape for consistent determination of border ownership Haruka Nishimura, Yoshihisa Tsuji, Ko Sakai Department of Computer Science, University of Tsukuba, Japan Border Ownership (BO) that indicates the side of figure along the border is an essence for figure/ground assignment. We propose a computational model for the BO determination based on the surround modulation (SM) reported in early visual areas. To examine the characteristics of the SM necessary for consistent BO determination among stimuli, we tested hundreds of the model cells, whose regions were given randomly, with a set of pseudo-random stimuli. Our analysis showed that the significant factor for the consistency is dominance of suppression that is a major physiological characteristic of SM. To analyze overall consistency of the model cells as a population, we compared the consistency of the model with the reaction time of human subjects, and found that a stimulus with the longer reaction time yields the lower consistency. The result provides phenomenological evidence for supporting SM in BO determination. Research funds: This work was supported by grant-in-aid from the Brain Science Foundation and the Okawa Foundation. HN is supported by KAKENHI for JSPS fellows, 17.7216