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Information processing of the human visual system analyzed by visual evoked potentials
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EXCITATION PROPAGATION IN VISUAL CORTICAL SLICES VISUALIZED BY OPTICAL RECORDING. HANABU TANIFUJI, RINTARO SUNABA, AND KEISUKE TOYAHA, N a t l . I n s t . P h y s i o l . S c i . , ~W_9_d~i.ii, Okazaki 444,.Jap_an. T r a n s v e r s e s l i c e s were d i s s e c t e d from a d u l t r a t v i s u a l c o r t e x (VC) and s t a i n e d w i t h a v o l t a g e s e n s i t i v e dye (RH482). The membrane p o t e n t i a l c h a n g e s in VC c e l l s p r o d u c e d by w h i t e m a t t e r (WH) s t i m u l a t i o n was d e t e r m i n e d as c h a n g e s i n l i g h t a b s o r b a n c e . E x c i t a t i o n p r o p a g a t i n g i n VC s l i c e s was v i s u a l i z e d as t i m e - l a p s e images by s t r o b i n g illumination at different time intervals (1 8 ms) a f t e r WH s t i m u l a t i o n . The o p t i c a l r e c o r d i n g t e c h n i q u e d e m o n s t r a t e d a s e q u e n c e o f e v e n t s : 1) a s h a r p wave p r o d u c e d i n t h e n e i g h b o r h o o d o f t h e c a t h o d e o f t h e s t i m u l a t i n g electrodes, representing impulses being propagated superficially, probably along the g e n i c u l a t e afferents, as w e l l as l a t e r a l l y , probably along the recurrent collaterals of the c o r t i c a l e f f e r e n t s ( i n t e r v a l , 1 ms), 2) m o n o s y n a p t i c e x c i t a t i o n p r o d u c e d i n l a y e r IV by g e n i c u l a t e i m p u l s e s , and t h a t i n l a y e r s V and VI by t h e recurrent impulses (3 ms), 3) polysynaptic excitation transferred to more superficial layers from layer IV (5 ms), and 4) higher order polysynaptic excitation transferred from layers II, III b a c k to layers V and VI. It was a l s o noted that the m a i n c o m p o n e n t of e x c i t a t i o n r e m a i n e d in a v e r t i c a l c o l u m n (about 500 um wide), e x t e n d i n g from the site of s t i m u l a t i o n to the c o r t i c a l surface, w i t h a weaker component extending laterally across the e n t i r e slice, w h i c h w o u l d be transferred by r e c u r r e n t collaterals of the efferents originating from each c o r t i c a l layer.
FUNCTIONAL MODULAR ORGANIZATION IN THE INFEROTEMPORAL CORTEX OF THE MACAQUE MONKEY. ICHIRO FUJITA, KANG CHENG*, AND KEIJI TANAKA, Lab. for Neural Information Processing, Frontier Research Program, RIKEN, Hirosawa 2-1, Wako, Saitama 351-01, Japan, The anterior part of the monkey inferotemporal cortex (AIT) is the final stage of a series of unimodal visual areas involved in object recognition. Most AIT cells selectively respond to particular visual images. To elucidate how visual information is represented in the AIT, we examined the relationship between stimulus selectivities of adjacent cells. Two Japanese monkeys were anesthetized with a mixture of N 2 0 and 02 and immobilized with gallamine triethiodide. We recorded simultaneously from several adjacent cells with a single electrode and determined stimulus features to activate these cells. Adjacent cells responded to similar features in most cases, although the optimal feature or the degree of tuning slightly differed among adjacent cells. We often observed cells with similar or related selectivity over a distance of more than 1 mm in penetrations directed vertically to the AIT surface. This suggests that these cells cluster across all cortical layers. Clusters of cells with similar, but slightly different s e l e c t i v i t i e s may form unit structures w h e r e stimulus features are represented by activity patterns across a cell population, or this clustering suggests that interaction among adjacent cells contributes to neuronal selectivity to visual stimuli.
INFORMATION PROCESSINGOF THE HUMANVISUAL SYSTE~ ANALYZED BY VISUAL EVOKED POTENTIALS. SHOZOTOBIMATSU'. SHIZUKA TASHIMA-KURITA'. MIYUKI NAKAYAMA-HIROMATSU'. AND MOTOHIROKATO. Department of Clinical Neurophysiology, Neurological Institute. Faculty of Medicine. Kvushu University 60, 3-I-1Maidashi, HigashiKu. Fukuoka 812. Japan. Visual evoked potentials (VEPs) were recorded in 12 young adults to study the information processing of the human visual system. Visual stimuli consisted of sinusoidal and square-wave 9ratin9~ and checkerboard pattern with the fundamental s p a t i a l frequency (SF) of 0.5-8 c/deg. For recording transient VEPs (T-VEPs). the pattern was a l t e r n a t e d a t a rate of 1Hz. ~hile f o r steady-state VEPs (S-VEPs) at 4 Hz and 8 Hz. I r r e s p e c t i v e of the types of the pattern, our major findings included; (l) the latency of the major p o s i t i v e component (PIO0) of T-MEPs was tuned to the fundamental SF of 2.0 c/deg, while the PIO0 amplitude did not show spatial tuning function. (2) the phase of the second harmonic response of S-VEPs f o r 4 Hz was tuned to the fundamental SF of 2.0 c/deg, while the amplitude did not show any tendency, and (3) the amplitude of S-VEPs for 8 Hz was tuned to the fundamental SF of 2.6 c/deg, while the phase did not show s p a t i a l s e l e c t i v i t y . These results suggest that the human visual system has the sp a t ia l tuning function to the fundamental SF of the pattern as a s p a t i a l frequency analyzer. The latency, phase and amplitude of VEPs may provide the d i f f e r e n t information about the visual system.
EXCITATION PROPAGATION IN VISUAL CORTICAL SLICES VISUALIZED BY OPTICAL RECORDING. HANABU TANIFUJI, RINTARO SUNABA, AND KEISUKE TOYAHA, N a t l . I n s t . P h y s i o l . S c i . , ~W_9_d~i.ii, Okazaki 444,.Jap_an. T r a n s v e r s e s l i c e s were d i s s e c t e d from a d u l t r a t v i s u a l c o r t e x (VC) and s t a i n e d w i t h a v o l t a g e s e n s i t i v e dye (RH482). The membrane p o t e n t i a l c h a n g e s in VC c e l l s p r o d u c e d by w h i t e m a t t e r (WH) s t i m u l a t i o n was d e t e r m i n e d as c h a n g e s i n l i g h t a b s o r b a n c e . E x c i t a t i o n p r o p a g a t i n g i n VC s l i c e s was v i s u a l i z e d as t i m e - l a p s e images by s t r o b i n g illumination at different time intervals (1 8 ms) a f t e r WH s t i m u l a t i o n . The o p t i c a l r e c o r d i n g t e c h n i q u e d e m o n s t r a t e d a s e q u e n c e o f e v e n t s : 1) a s h a r p wave p r o d u c e d i n t h e n e i g h b o r h o o d o f t h e c a t h o d e o f t h e s t i m u l a t i n g electrodes, representing impulses being propagated superficially, probably along the g e n i c u l a t e afferents, as w e l l as l a t e r a l l y , probably along the recurrent collaterals of the c o r t i c a l e f f e r e n t s ( i n t e r v a l , 1 ms), 2) m o n o s y n a p t i c e x c i t a t i o n p r o d u c e d i n l a y e r IV by g e n i c u l a t e i m p u l s e s , and t h a t i n l a y e r s V and VI by t h e recurrent impulses (3 ms), 3) polysynaptic excitation transferred to more superficial layers from layer IV (5 ms), and 4) higher order polysynaptic excitation transferred from layers II, III b a c k to layers V and VI. It was a l s o noted that the m a i n c o m p o n e n t of e x c i t a t i o n r e m a i n e d in a v e r t i c a l c o l u m n (about 500 um wide), e x t e n d i n g from the site of s t i m u l a t i o n to the c o r t i c a l surface, w i t h a weaker component extending laterally across the e n t i r e slice, w h i c h w o u l d be transferred by r e c u r r e n t collaterals of the efferents originating from each c o r t i c a l layer.
FUNCTIONAL MODULAR ORGANIZATION IN THE INFEROTEMPORAL CORTEX OF THE MACAQUE MONKEY. ICHIRO FUJITA, KANG CHENG*, AND KEIJI TANAKA, Lab. for Neural Information Processing, Frontier Research Program, RIKEN, Hirosawa 2-1, Wako, Saitama 351-01, Japan, The anterior part of the monkey inferotemporal cortex (AIT) is the final stage of a series of unimodal visual areas involved in object recognition. Most AIT cells selectively respond to particular visual images. To elucidate how visual information is represented in the AIT, we examined the relationship between stimulus selectivities of adjacent cells. Two Japanese monkeys were anesthetized with a mixture of N 2 0 and 02 and immobilized with gallamine triethiodide. We recorded simultaneously from several adjacent cells with a single electrode and determined stimulus features to activate these cells. Adjacent cells responded to similar features in most cases, although the optimal feature or the degree of tuning slightly differed among adjacent cells. We often observed cells with similar or related selectivity over a distance of more than 1 mm in penetrations directed vertically to the AIT surface. This suggests that these cells cluster across all cortical layers. Clusters of cells with similar, but slightly different s e l e c t i v i t i e s may form unit structures w h e r e stimulus features are represented by activity patterns across a cell population, or this clustering suggests that interaction among adjacent cells contributes to neuronal selectivity to visual stimuli.
INFORMATION PROCESSINGOF THE HUMANVISUAL SYSTE~ ANALYZED BY VISUAL EVOKED POTENTIALS. SHOZOTOBIMATSU'. SHIZUKA TASHIMA-KURITA'. MIYUKI NAKAYAMA-HIROMATSU'. AND MOTOHIROKATO. Department of Clinical Neurophysiology, Neurological Institute. Faculty of Medicine. Kvushu University 60, 3-I-1Maidashi, HigashiKu. Fukuoka 812. Japan. Visual evoked potentials (VEPs) were recorded in 12 young adults to study the information processing of the human visual system. Visual stimuli consisted of sinusoidal and square-wave 9ratin9~ and checkerboard pattern with the fundamental s p a t i a l frequency (SF) of 0.5-8 c/deg. For recording transient VEPs (T-VEPs). the pattern was a l t e r n a t e d a t a rate of 1Hz. ~hile f o r steady-state VEPs (S-VEPs) at 4 Hz and 8 Hz. I r r e s p e c t i v e of the types of the pattern, our major findings included; (l) the latency of the major p o s i t i v e component (PIO0) of T-MEPs was tuned to the fundamental SF of 2.0 c/deg, while the PIO0 amplitude did not show spatial tuning function. (2) the phase of the second harmonic response of S-VEPs f o r 4 Hz was tuned to the fundamental SF of 2.0 c/deg, while the amplitude did not show any tendency, and (3) the amplitude of S-VEPs for 8 Hz was tuned to the fundamental SF of 2.6 c/deg, while the phase did not show s p a t i a l s e l e c t i v i t y . These results suggest that the human visual system has the sp a t ia l tuning function to the fundamental SF of the pattern as a s p a t i a l frequency analyzer. The latency, phase and amplitude of VEPs may provide the d i f f e r e n t information about the visual system.