- Email: [email protected]
Line length selective masking
215 immediate neighbours. It is, therefore, concluded that in area 17 of the cat the orientation domain has a continuous spatial and functional representation. 1 HUBEL, D. H., AND WIESEL) T. N., Receptive fields, binocular interaction and functional architec-
ture in the cat's visual cortex, J. Physiol. (Lond.), 160 (1962) 106-154. 2 HtraEL, D. H., AND WmSEL,T. N., Shape and arrangement of columns in cat's striate cortex, J. Physiol. (Lond.), 165 (1963) 559-568.
Line length selective masking KEN SHIINA AND R. B. FREEMAN, JR. - - Tottori University, Japan and University of
Constance, Constance (G.F.R.) In a series of experiments, we investigated a relatively higher order of stimulus feature selectivity: line length selective backward and forward masking. The test (T) stimulus was one of 12 upper case letters of the alphabet drawn so that all strokes of a single letter had the same line length. The masking (M) stimulus consisted o f a p a t t e r n of lines of equal lengths which were spatially randomly distributed and oriented so as to avoid overlap of the lines. These T- and M-stimulus pairs were prepared with 3 different line lengths (15, 30 and 60 min of arc) but with a constant line width. A fourth masking stimulus composed of randomly distributed dots was also used. The 4 M-stimulus patterns and 3 T-stimulus sizes were presented tachistoscopically in all possible permutations. The subject's task was to identify the T-stimulus letter correctly. Both monocular and dichoptic thresholds were determined under conditions of forward and backward masking. The results showed size-selective masking effects in backward as well as forward masking situations: in the 3 T- and M-stimulus conditions in which line lengths were equal, the masking effect was greater than in corresponding conditions involving unequal T- and M-stimulus line lengths. The size-selective masking effect was shown rather more clearly in dichoptic than in monoptic observation. The results are neither explainable in terms of stimulus confusion nor by interception of information processing. Contour overlap between the letter and the masking lines must also be ruled out as the responsible factor for these effects. Rather we conclude that the results may be attributed to non-retinotopic tuning of line length at a level of the visual system higher than that of the coding processes of simple and complex cells.
Visual responses of hypothalemic neurones M. J. BtrRTON, E. T. ROLLSAND F. MORA - - Department of ExperimentaIPsychology,
University of Oxford, Oxford (Great Britain) We have made recordings from several hundred different neurones in the far
ture in the cat's visual cortex, J. Physiol. (Lond.), 160 (1962) 106-154. 2 HtraEL, D. H., AND WmSEL,T. N., Shape and arrangement of columns in cat's striate cortex, J. Physiol. (Lond.), 165 (1963) 559-568.
Line length selective masking KEN SHIINA AND R. B. FREEMAN, JR. - - Tottori University, Japan and University of
Constance, Constance (G.F.R.) In a series of experiments, we investigated a relatively higher order of stimulus feature selectivity: line length selective backward and forward masking. The test (T) stimulus was one of 12 upper case letters of the alphabet drawn so that all strokes of a single letter had the same line length. The masking (M) stimulus consisted o f a p a t t e r n of lines of equal lengths which were spatially randomly distributed and oriented so as to avoid overlap of the lines. These T- and M-stimulus pairs were prepared with 3 different line lengths (15, 30 and 60 min of arc) but with a constant line width. A fourth masking stimulus composed of randomly distributed dots was also used. The 4 M-stimulus patterns and 3 T-stimulus sizes were presented tachistoscopically in all possible permutations. The subject's task was to identify the T-stimulus letter correctly. Both monocular and dichoptic thresholds were determined under conditions of forward and backward masking. The results showed size-selective masking effects in backward as well as forward masking situations: in the 3 T- and M-stimulus conditions in which line lengths were equal, the masking effect was greater than in corresponding conditions involving unequal T- and M-stimulus line lengths. The size-selective masking effect was shown rather more clearly in dichoptic than in monoptic observation. The results are neither explainable in terms of stimulus confusion nor by interception of information processing. Contour overlap between the letter and the masking lines must also be ruled out as the responsible factor for these effects. Rather we conclude that the results may be attributed to non-retinotopic tuning of line length at a level of the visual system higher than that of the coding processes of simple and complex cells.
Visual responses of hypothalemic neurones M. J. BtrRTON, E. T. ROLLSAND F. MORA - - Department of ExperimentaIPsychology,
University of Oxford, Oxford (Great Britain) We have made recordings from several hundred different neurones in the far