Contrast response of a movement-encoding system.
J Opt Soc Am A Opt Image Sci Vis
; 12(6): 1185-97, 1995 Jun.
Article
en En
| MEDLINE
| ID: mdl-7769505
ABSTRACT
The ability to identify the direction of apparent motion in a sequence of two short light pulses of different amplitudes at separate spatial locations was studied. The product of pulse amplitudes is a very poor predictor of such performance when one of the two signals is much higher in amplitude than the other above a certain amplitude the probability of correct identification becomes virtually independent of the amplitude of the larger pulse. There was no noticeable difference in performance between low-high and high-low contrast sequences. Both the direction identification and the simple contrast-detection probabilities can be represented by the same psychometric function of the luminance increment delta L, provided that delta L is normalized by the nth power of the background luminance level, Lb. These results suggest that the general Reichardt-type scheme of movement encoding should be modified in the manner proposed for the fly's visual system [J. Opt. Soc. Am. A 6, 116 (1989)] (1) the mean luminance is subtracted from the input signal before the signal is subjected to a nonlinear compression and (2) saturation characteristics are inserted into both branches of the two mirror-symmetric motion-detection subunits before multiplication of the input signals. The identical metric of the contrast response suggests that movement discrimination and luminance detection are two different special-purpose computations performed on the output of the same encoding network.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Sensibilidad de Contraste
/
Percepción de Movimiento
/
Movimiento
Tipo de estudio:
Prognostic_studies
Límite:
Humans
Idioma:
En
Revista:
J Opt Soc Am A Opt Image Sci Vis
Asunto de la revista:
OFTALMOLOGIA
Año:
1995
Tipo del documento:
Article
País de afiliación:
Estonia