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1621 Motion aftereffect on saccadic eye movements
S182
1620
THE HUMAN COUNTERPART OF THE DORSAL MEDIAL-SUPERIOR-TEMPORAL AREA AS REVEALED BY POSITRON EMISSION TOMOGRAPHY. KANG CHENG l, HIDEAKI FUJITA 3, IWAO KANNO 3, SHUICHI MIURA 3, AND KEIJI TANAKAI,2, 1Lab. for Neural Into. Processing, and 21nfo. Sci. Lab., RIKEN~ Wake 351~ Japan and 3Dept. of Radiology & Nuclear Med., Res. Inst. for Brain & Blood Vessels, Akita 010, Japan. Most cells in the dorsal part of the medial superior temporal area (dMST) in monkey have large receptive fields and respond preferentially to the movement of a wide textured field rather than to that of a small stimulus. The dMST has thus been thought to be involved in the analysis of wide-field movement caused by movements of animal itself. We have used positron emission tomography (PET) to monitor stimuli-evoked changes in cerebral blood flow (CBF) and used subtraction technique to map the functional loci engaged in analysis of wide-field movement in normal human subjects. The 2 test conditions reported here included 2 arrays of moving dots on a gray background which were identical in dot/background contrast (0.15 log unit), size of dots (1" in diam.), density el dots (1.2%), and speed of motion (32°/s), but were different in motion -- in the first condition, all dots moved coherently in one of 8 directions (45° apart) which changed every l-s, whereas in the second condition, each dot moved in a ron0Qm direction• The control condition was a blank gray background without dots. The stimuli were made on a VTR system (30 frames/s) and were played back on a 5" liquid crystal TV display accommodated within the PET scanner. During 90-s data acquisition of PET scan in each condition (2 scans per condition), the subject had to use his left eye to fixate on a cross in the center of the display through a lens so that the display field could extend up to 80x80°. Subtraction was made between 2 test images and the control image, as well as between coherent and r~nOQmimages (~ - r Image), and were anatomically standardized for each subject based on a standard Japanese brain and averaged across 10 subjects (all male Japanese). The average ~ - r image revealed statistically significant (t-analysis) CBF increase in several brain areas, including a left-dominant but bilateral activation in a region extending from the posterior superior temporal gyms (Brodmann area 22) to the ventral angular gyrus (area 39), which may be the counterpart of dMST in human visual cortex.
1621
MOTION
AFTEREFFECT
ON
SACCADIC
EYE
MOVEMENTS.
TADASHI
OGAWA
and
M A S A H I K O FUJITA, Communications Reserarch Lab. M.P.T., 4-2-1 Nukuikita-machi, Koganei-shi, Tokyo 184, Japan
We investigated the motion aftereffect (MAE) on saccadic eye m o v e m e n t s in o r d e r to clarify the r e l a t i o n s h i p b e t w e e n motion and p o s i t i o n p e r c e p t i o n in h u m a n v i s u a l i n f o r m a t i o n p r o c e s s i n g . The information of target position is used in planning saccades m a d e to a stationary target,
but in planning
s a c c a d e s to a moving target, both target position and target velocity information must be involved. We investigated the characteristics of these two types of horizontal saccadic eye movements to a target under rightward or leftward directed MAE. S a c c a d e s made to a moving target are less accurate than those made to a stationary target. When the moving target and MAE were in the s a m e direction, saccades t e n d e d to be hypermetric, but in the opposite direction they tended to be hypometric. T h e s e results suggest that the target motion was perceptually biased opposite to the MAE direction.
1622
RETINOTOPIC ORGANIZATION OF VISUAL CORTEX REVEALED BY VISUAL EVOKED MAGNETIC FIELDS. ATSUSHI NAMBU, RYUICHI MATSUZAKI, TORU TSUJIMOTO AND SH1N-
ICHI KYUHO Dept. of Integrative Physiology, National Institute for Physiological Sciences, Okazaki 444, Japan A non-invasive technique, magnetoencephalography (MEG) is considered to be useful in estimating active loci in the human brain. Visual stimuli were presented at 4 or 8 positions around the center of the visual field through fiber optics. Magnetic fields over the occipital part of scalp were recorded with a 37-channel first-order SQUID gradiometer system (BTi, CA), and were averaged 100-400 times at the onset of visual stimuli. Several components were identified. Waveform and distribution of the responses in the 37 channels greatly varied depending on the stimulus position within the visual field. The first component (peak latency, around 70 ms) was small (<50 IF) and was not always observed. The second component (around 100 ms) was large (50-100 IT), and the electrical current dipole responsible for the magnetic field was estimated around the midline of the occipital lobe, presumably the striate cortex. The third component was large (50-100 IT), but did not show a simple dipolar pattern. 'this component may originate from the extra-striate cortex in addition to the striate cortex. Further studies should be made on the integrative visual functions in human subjects.
1620
THE HUMAN COUNTERPART OF THE DORSAL MEDIAL-SUPERIOR-TEMPORAL AREA AS REVEALED BY POSITRON EMISSION TOMOGRAPHY. KANG CHENG l, HIDEAKI FUJITA 3, IWAO KANNO 3, SHUICHI MIURA 3, AND KEIJI TANAKAI,2, 1Lab. for Neural Into. Processing, and 21nfo. Sci. Lab., RIKEN~ Wake 351~ Japan and 3Dept. of Radiology & Nuclear Med., Res. Inst. for Brain & Blood Vessels, Akita 010, Japan. Most cells in the dorsal part of the medial superior temporal area (dMST) in monkey have large receptive fields and respond preferentially to the movement of a wide textured field rather than to that of a small stimulus. The dMST has thus been thought to be involved in the analysis of wide-field movement caused by movements of animal itself. We have used positron emission tomography (PET) to monitor stimuli-evoked changes in cerebral blood flow (CBF) and used subtraction technique to map the functional loci engaged in analysis of wide-field movement in normal human subjects. The 2 test conditions reported here included 2 arrays of moving dots on a gray background which were identical in dot/background contrast (0.15 log unit), size of dots (1" in diam.), density el dots (1.2%), and speed of motion (32°/s), but were different in motion -- in the first condition, all dots moved coherently in one of 8 directions (45° apart) which changed every l-s, whereas in the second condition, each dot moved in a ron0Qm direction• The control condition was a blank gray background without dots. The stimuli were made on a VTR system (30 frames/s) and were played back on a 5" liquid crystal TV display accommodated within the PET scanner. During 90-s data acquisition of PET scan in each condition (2 scans per condition), the subject had to use his left eye to fixate on a cross in the center of the display through a lens so that the display field could extend up to 80x80°. Subtraction was made between 2 test images and the control image, as well as between coherent and r~nOQmimages (~ - r Image), and were anatomically standardized for each subject based on a standard Japanese brain and averaged across 10 subjects (all male Japanese). The average ~ - r image revealed statistically significant (t-analysis) CBF increase in several brain areas, including a left-dominant but bilateral activation in a region extending from the posterior superior temporal gyms (Brodmann area 22) to the ventral angular gyrus (area 39), which may be the counterpart of dMST in human visual cortex.
1621
MOTION
AFTEREFFECT
ON
SACCADIC
EYE
MOVEMENTS.
TADASHI
OGAWA
and
M A S A H I K O FUJITA, Communications Reserarch Lab. M.P.T., 4-2-1 Nukuikita-machi, Koganei-shi, Tokyo 184, Japan
We investigated the motion aftereffect (MAE) on saccadic eye m o v e m e n t s in o r d e r to clarify the r e l a t i o n s h i p b e t w e e n motion and p o s i t i o n p e r c e p t i o n in h u m a n v i s u a l i n f o r m a t i o n p r o c e s s i n g . The information of target position is used in planning saccades m a d e to a stationary target,
but in planning
s a c c a d e s to a moving target, both target position and target velocity information must be involved. We investigated the characteristics of these two types of horizontal saccadic eye movements to a target under rightward or leftward directed MAE. S a c c a d e s made to a moving target are less accurate than those made to a stationary target. When the moving target and MAE were in the s a m e direction, saccades t e n d e d to be hypermetric, but in the opposite direction they tended to be hypometric. T h e s e results suggest that the target motion was perceptually biased opposite to the MAE direction.
1622
RETINOTOPIC ORGANIZATION OF VISUAL CORTEX REVEALED BY VISUAL EVOKED MAGNETIC FIELDS. ATSUSHI NAMBU, RYUICHI MATSUZAKI, TORU TSUJIMOTO AND SH1N-
ICHI KYUHO Dept. of Integrative Physiology, National Institute for Physiological Sciences, Okazaki 444, Japan A non-invasive technique, magnetoencephalography (MEG) is considered to be useful in estimating active loci in the human brain. Visual stimuli were presented at 4 or 8 positions around the center of the visual field through fiber optics. Magnetic fields over the occipital part of scalp were recorded with a 37-channel first-order SQUID gradiometer system (BTi, CA), and were averaged 100-400 times at the onset of visual stimuli. Several components were identified. Waveform and distribution of the responses in the 37 channels greatly varied depending on the stimulus position within the visual field. The first component (peak latency, around 70 ms) was small (<50 IF) and was not always observed. The second component (around 100 ms) was large (50-100 IT), and the electrical current dipole responsible for the magnetic field was estimated around the midline of the occipital lobe, presumably the striate cortex. The third component was large (50-100 IT), but did not show a simple dipolar pattern. 'this component may originate from the extra-striate cortex in addition to the striate cortex. Further studies should be made on the integrative visual functions in human subjects.