Correlation between the rising slope of lens accommodation responses and lens-related neuronal...
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S178 GABAERGIC INHIBITION IN THE SUPERFICIAL LAYERS OF CAT SUPERIOR COLLICULUS. TORU TAKIMORI, *I TETSURO OGAWA, 1 AND KOICHI IIJIMA, 2 Departments of iphysiology, 2Anatomy, Akita University School of Medicine, i-I-I Hondo, Akita-shi, Japan. Using chloralose-anesthetized cats, we investigated a GABAergic inhibitory mechanism in superficial layers of the superior colliculus. Bipolar stimulating electrodes were stereotaxically placed in the optic chiasm(OX) and optic tract(OT). Multibarreled glass microelectrodes were used for recording unit discharges extracellularly and for applying GABA, bicuculline and NaCI by iontophoresis. Recording sites of all units studied were checked with reference to Pontamine Sky Blue marking spots. Application of GABA suppressed the spike discharges evoked by OT or OX stimulation or occurring spontaneously. This suppression was observed on cells located in layers I, II, and III, especially in the middle part of layer II where about 70% of cells studied were suppressed. Bieuculline blocked GABA's effects as well as an inhibition induced by OT/OX stimulation. These findings support the idea that the inhibition is mediated by GABA and that the majority of neurons in layer II have at least GABA A receptors. Based on these physiological results we made an immunocytochemical study of intrinsic GABAergic neurons, using an antiserum raised against bovine serum albumin-conjugated GABA. Neurons labeled by the GABA antibody were densest in layer II, although less numerous labeled neurons were found in layer III. The ratio of labeled to unlabeled neurons was ca. 30% in layer II. CORRELATION BETWEENTF~ERISING SI/laE OF LENS ACLX]MM3DATIONRESPONSES AND L~NS-RELATED NEURONAL ACTIVITIES IN THE LATERAL SUPRASYLVIANAREA IN CATS. TAF~IKO BANDOAND HARUOTODA r Department of Physiology, Niigata University School of Medicine F Asahimachi, Niigata F Niiqata 951 Japan. Lens-related neuronal activities in the lateral suprasylvian area (LSA) in cats were cor- related to spontaneous and evoked changes of dioptric power of the eye. Chronically operated cats were anesthetized with N20/O2, and immobilized with gallamine triethiodide. Lens accom- modation of the right eye was monitored using an infrared optometer. Visual properties were tested manually and the reoeptive field of each LSA neuron was determined in the frontoparallel screen. For quantitative analysis, a target was driven by a laboratory computer in depth. Tnirteen of 184 LSA neurons were lens-related: they discharged 200-1000 msec (450 ~ 220 msec) before the onset of spontaneous lens aouu,|,odation, and dioptric power of the eye was increased by microstimulation at the recording sites. The n~nber of spikes of lens-related neurons during 700 msec just prior to the onset of a~ation correlated significantly to rising slopes of acc~,,,~dation. Lens-related neurons responded to the movement of the target in depth. Five of 13 lens-related units selectively responded to approaching target, and 8 responded to movement of the target both in depth and in fronto-parallel plane. Visual activities of lens-related neurons followed the movement of targets, and preceded the increase of dioptric power. In a few lens-related neurons, nummber of spikes just prior to a ~ t i o n correlated to rising slopes of evoked accommodation. These results suggest that LSA plays important roles in processing visual information related to the dynamic aspect of lens acoommodation, transforming it to motor-related neural signal and transmitting it to themotor nuclei in the brainstem. CROSS-CORRELATION ANALYSIS OF INHIBITORY INTERACTION BETWEEN ORIENTATION COLUMNS IN CAT VISUAL CORTEX. YOSHIO HATA', TADAHARU TSUMOTO, HIROMICHI SATO, KOUICHIRO HAGIHARA', AND HIROSI TAMURA', Department of Neurophyslology, Biomedical Research Center, Osaka University Medical School, 4-3- 57, Kltaku, Osaka, 530 Japan. Neurons In the visual cortex are selectively responsive to light or dark bars presented at particular orientations. Intracortlcal inhibition is hypothesized to contribute to this orienta- tion selectivity. However, the presence of intracortical connections mediating inhibition for orientation selectivity is controversial. The present study explored properties of inhibitory connections between visual cortical neurons. Spike discharges of pairs of cells were recorded simultaneously from the cat primary visual cortex. The animals were anesthetized with 70~ N20-30~ 02. Halothane was added to the gas when necessary to maintain an adequate depth of anesthesia. The receptive field properties of each cell were explored and cross-correlograms were constructed from the pair of spike trains. Significant inhibitory interactions were found in 10 of the 310 pairs of cells that were separated horizontally by less than 1 mm, which is the approximate diameter of a "hypereolumn". Inhibitory interactions were observed in 4 pairs with difference in optimal orientations less than 22", and in 6 pairs with differences between 23" and 45". No inhibitory interaction was found in pairs with orientation difference more than 45'. As to the laminar location of the cells, 9 pairs with inhibitory interactions were in the same layer and one was in the neighboring layer. These results demonstrate that horizontal inhibitory interactions exist between visual cortical cells with somewhat different orientation preferences, but appear not to exist between those with orthognnal preferences.
Transcript of Correlation between the rising slope of lens accommodation responses and lens-related neuronal...
S178
GABAERGIC INHIBITION IN THE SUPERFICIAL LAYERS OF CAT SUPERIOR COLLICULUS. TORU TAKIMORI, *I TETSURO OGAWA, 1 AND KOICHI IIJIMA, 2 Departments of iphysiology, 2Anatomy, Akita University School of Medicine, i-I-I Hondo, Akita-shi, Japan.
Using chloralose-anesthetized cats, we investigated a GABAergic inhibitory mechanism in superficial layers of the superior colliculus. Bipolar stimulating electrodes were stereotaxically placed in the optic chiasm(OX) and optic tract(OT). Multibarreled glass microelectrodes were used for recording unit discharges extracellularly and for applying GABA, bicuculline and NaCI by iontophoresis. Recording sites of all units studied were checked with reference to Pontamine Sky Blue marking spots. Application of GABA suppressed the spike discharges evoked by OT or OX stimulation or occurring spontaneously. This suppression was observed on cells located in layers I, II, and III, especially in the middle part of layer II where about 70% of cells studied were suppressed. Bieuculline blocked GABA's effects as well as an inhibition induced by OT/OX stimulation. These findings support the idea that the inhibition is mediated by GABA and that the majority of neurons in layer II have at least GABA A receptors. Based on these physiological results we made an immunocytochemical study of intrinsic GABAergic neurons, using an antiserum raised against bovine serum albumin-conjugated GABA. Neurons labeled by the GABA antibody were densest in layer II, although less numerous labeled neurons were found in layer III. The ratio of labeled to unlabeled neurons was ca. 30% in layer II.
CORRELATION BETWEENTF~ERISING SI/ laE OF LENS ACLX]MM3DATIONRESPONSES AND L~NS-RELATED NEURONAL ACTIVITIES IN THE LATERAL SUPRASYLVIANAREA IN CATS. TAF~IKO BANDOAND HARUOTODA r Department of Physiology, Niigata University School of Medicine F Asahimachi, Niigata F Niiqata 951 Japan.
Lens-related neuronal activities in the lateral suprasylvian area (LSA) in cats were cor- related to spontaneous and evoked changes of dioptric power of the eye. Chronically operated cats were anesthetized with N20/O2, and immobilized with gallamine triethiodide. Lens accom- modation of the right eye was monitored using an infrared optometer. Visual properties were tested manually and the reoeptive field of each LSA neuron was determined in the frontoparallel screen. For quantitative analysis, a target was driven by a laboratory computer in depth. Tnirteen of 184 LSA neurons were lens-related: they discharged 200-1000 msec (450 ~ 220 msec) before the onset of spontaneous lens aouu,|,odation, and dioptric power of the eye was increased by microstimulation at the recording sites. The n~nber of spikes of lens-related neurons during 700 msec just prior to the onset of a~ation correlated significantly to rising slopes of acc~,,,~dation. Lens-related neurons responded to the movement of the target in depth. Five of 13 lens-related units selectively responded to approaching target, and 8 responded to movement of the target both in depth and in fronto-parallel plane. Visual activities of lens-related neurons followed the movement of targets, and preceded the increase of dioptric power. In a few lens-related neurons, nummber of spikes just prior to a ~ t i o n correlated to rising slopes of evoked accommodation. These results suggest that LSA plays important roles in processing visual information related to the dynamic aspect of lens acoommodation, transforming it to motor-related neural signal and transmitting it to themotor nuclei in the brainstem.
CROSS-CORRELATION ANALYSIS OF INHIBITORY INTERACTION BETWEEN ORIENTATION COLUMNS IN CAT VISUAL CORTEX. YOSHIO HATA', TADAHARU TSUMOTO, HIROMICHI SATO, KOUICHIRO HAGIHARA', AND HIROSI TAMURA', Department of N e u r o p h y s l o l o g y , B i o m e d i c a l Research Cen te r , Osaka U n i v e r s i t y Medical School , 4-3- 57, K l t aku , Osaka, 530 Japan .
Neurons In t he v i s u a l c o r t e x a r e s e l e c t i v e l y r e s p o n s i v e to l i g h t or da rk b a r s p r e s e n t e d a t p a r t i c u l a r o r i e n t a t i o n s . I n t r a c o r t l c a l i n h i b i t i o n i s h y p o t h e s i z e d to c o n t r i b u t e to t h i s o r i e n t a - t i o n s e l e c t i v i t y . However, t he p r e s e n c e of i n t r a c o r t i c a l c o n n e c t i o n s m e d i a t i n g i n h i b i t i o n fo r o r i e n t a t i o n s e l e c t i v i t y i s c o n t r o v e r s i a l . The p r e s e n t s t u d y e x p l o r e d p r o p e r t i e s of i n h i b i t o r y c o n n e c t i o n s between v i s u a l c o r t i c a l neu rons . Spike d i s c h a r g e s of p a i r s of c e l l s were r eco rded s i m u l t a n e o u s l y from the c a t p r i m a r y v i s u a l c o r t e x . The a n i m a l s were a n e s t h e t i z e d w i t h 70~ N20-30~ 02. Ha lo thane was added to t he gas when n e c e s s a r y to m a i n t a i n an adequa te depth of a n e s t h e s i a . The r e c e p t i v e f i e l d p r o p e r t i e s of each c e l l were e x p l o r e d and c r o s s - c o r r e l o g r a m s were c o n s t r u c t e d from the p a i r of s p i k e t r a i n s . S i g n i f i c a n t i n h i b i t o r y i n t e r a c t i o n s were found in 10 of the 310 p a i r s of c e l l s t h a t were s e p a r a t e d h o r i z o n t a l l y by l e s s than 1 mm, which i s the app rox ima te d i a m e t e r of a "hypereo lumn" . I n h i b i t o r y i n t e r a c t i o n s were o b s e r v e d in 4 p a i r s w i th d i f f e r e n c e in o p t i m a l o r i e n t a t i o n s l e s s than 22", and in 6 p a i r s w i th d i f f e r e n c e s between 23" and 45". No i n h i b i t o r y i n t e r a c t i o n was found in p a i r s w i t h o r i e n t a t i o n d i f f e r e n c e more than 4 5 ' . As to the l a m i n a r l o c a t i o n of the c e l l s , 9 p a i r s w i t h i n h i b i t o r y i n t e r a c t i o n s were in the same l a y e r and one was i n the n e i g h b o r i n g l a y e r . These r e s u l t s d e m o n s t r a t e t h a t h o r i z o n t a l i n h i b i t o r y i n t e r a c t i o n s e x i s t between v i s u a l c o r t i c a l c e l l s w i t h somewhat d i f f e r e n t o r i e n t a t i o n p r e f e r e n c e s , but appear not to e x i s t between t h o s e w i t h o r t h o g n n a l p r e f e r e n c e s .
