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Wavelength - without brightness - processing in visual field defects: A hypothesis
239 REFERENCES I.
Kossut, M. and Rose, S.P.R., Neurosci., 12 (1984) 971-977,
2.
Stewart, M.G., King, T.S. and Rose, S.P.R., Acta Stereologica, 2, no I(1983) 227-230.
3.
Stewart, M.G., C s i l l a g , A. and Rose, S.P.R. (in preparation).
4.
Dyson, S.E. and Jones, D.G., Brain Res., 183 (1980) 43-59.
WAVELENGTH - WITHOUT BRIGHTNESS - PROCESSING IN VISUAL FIELD DEFECTS: A HYPOTHESIS STOERIG, P. I n s t i t u t f u r Medizinische Psychologie der Ludwig-Maximilians-Universit~t MUnchen, 8 MUnchen 2, West-Germany Under photopic viewing c o n d i t i o n s , colour and luminance perception are normally inseparable. In contrast, in visual f i e l d defects caused by postgeniculate lesions, wavelength could be shown to be dissociated from brightness processing. With a signal detection procedure, 6 of 10 patients were found to both discriminate and detect red an green targets (44', 10 cd/sqm) that were succesively presented (200 ms) at a r e l a t i v e l y central position in t h e i r b l i n d f i e l d .
However, at the same r e t i -
nal p o s i t i o n , the patients could not detect a white target (16 cd/sqm, 4 4 ' ) , or discriminate between two white targets d i f f e r i n g in luminous f l u x (16 vs 160 cd/sqm, 4 4 ' ) . To explain t h i s e f f e c t , a neuronal substrate has to be assumed that reacts b e t t e r , or e x c l u s i v e l y , to wavelength information. Apart from double-opponent c e l l s found in the cortex, only colour-opponent c e l l s in the l a t e r a l gen i c u l a t e body have been reported to react stronger to coloured l i g h t , provided the stimulus was l a r I ger than the receptive f i e l d centre of the c e l l tested . In combination with t h i s stimulus-size dependent antagonism for brightness information, the colour-synergism could explain the observed dissociation: As the colour-opponent system degenerates strongly a f t e r a postgeniculate l e s i o n , a r e s i dual visual f u n c t i o n mediated by t h i s system could depend on the functional c h a r a c t e r i s t i c s of i t s few s u r v i v i n g c e l l s . REFERENCES I.
De Valois et a l . , Sensory Processes I (1977).
THE EFFECT OF AMINO-PHOSPHONOBUTYRICACID (APB) AND OF ClS-2,3-PIPERIDINE DICARBOXYLIC ACID (PDA) ON FLASH RESPONSES OF RETINAL GANGLION CELLS SUCHER, N., PRZYBYSZEWSKI,A. AND GRUSSER, O.-J. Dept. of Physiology, Freie U n i v e r s i t ~ t , Arnimallee 22, Berlin 33, Germany L-APB, D-APB or PDA was injected into the vitreous body of the cat eye. Single ganglion c e l l activity
was recorded from optic t r a c t axons by means of microelectrodes. The L-APB at a dose above
0.5 mg per eye led to a decrease in on-center neuron spontaneous a c t i v i t y and a reduction or a b o l i t i o n of flash-evoked responses, while in o f f - c e n t e r neurons the flash-induced i n h i b i t o r y period was
Kossut, M. and Rose, S.P.R., Neurosci., 12 (1984) 971-977,
2.
Stewart, M.G., King, T.S. and Rose, S.P.R., Acta Stereologica, 2, no I(1983) 227-230.
3.
Stewart, M.G., C s i l l a g , A. and Rose, S.P.R. (in preparation).
4.
Dyson, S.E. and Jones, D.G., Brain Res., 183 (1980) 43-59.
WAVELENGTH - WITHOUT BRIGHTNESS - PROCESSING IN VISUAL FIELD DEFECTS: A HYPOTHESIS STOERIG, P. I n s t i t u t f u r Medizinische Psychologie der Ludwig-Maximilians-Universit~t MUnchen, 8 MUnchen 2, West-Germany Under photopic viewing c o n d i t i o n s , colour and luminance perception are normally inseparable. In contrast, in visual f i e l d defects caused by postgeniculate lesions, wavelength could be shown to be dissociated from brightness processing. With a signal detection procedure, 6 of 10 patients were found to both discriminate and detect red an green targets (44', 10 cd/sqm) that were succesively presented (200 ms) at a r e l a t i v e l y central position in t h e i r b l i n d f i e l d .
However, at the same r e t i -
nal p o s i t i o n , the patients could not detect a white target (16 cd/sqm, 4 4 ' ) , or discriminate between two white targets d i f f e r i n g in luminous f l u x (16 vs 160 cd/sqm, 4 4 ' ) . To explain t h i s e f f e c t , a neuronal substrate has to be assumed that reacts b e t t e r , or e x c l u s i v e l y , to wavelength information. Apart from double-opponent c e l l s found in the cortex, only colour-opponent c e l l s in the l a t e r a l gen i c u l a t e body have been reported to react stronger to coloured l i g h t , provided the stimulus was l a r I ger than the receptive f i e l d centre of the c e l l tested . In combination with t h i s stimulus-size dependent antagonism for brightness information, the colour-synergism could explain the observed dissociation: As the colour-opponent system degenerates strongly a f t e r a postgeniculate l e s i o n , a r e s i dual visual f u n c t i o n mediated by t h i s system could depend on the functional c h a r a c t e r i s t i c s of i t s few s u r v i v i n g c e l l s . REFERENCES I.
De Valois et a l . , Sensory Processes I (1977).
THE EFFECT OF AMINO-PHOSPHONOBUTYRICACID (APB) AND OF ClS-2,3-PIPERIDINE DICARBOXYLIC ACID (PDA) ON FLASH RESPONSES OF RETINAL GANGLION CELLS SUCHER, N., PRZYBYSZEWSKI,A. AND GRUSSER, O.-J. Dept. of Physiology, Freie U n i v e r s i t ~ t , Arnimallee 22, Berlin 33, Germany L-APB, D-APB or PDA was injected into the vitreous body of the cat eye. Single ganglion c e l l activity
was recorded from optic t r a c t axons by means of microelectrodes. The L-APB at a dose above
0.5 mg per eye led to a decrease in on-center neuron spontaneous a c t i v i t y and a reduction or a b o l i t i o n of flash-evoked responses, while in o f f - c e n t e r neurons the flash-induced i n h i b i t o r y period was