CONTRAST SENSITIVITY AND ACUITY OF THE GOLDFISH

Photopic contrast thresholds to sinusoidal gratings were measured in five goldfish by conditioning respiration in a Pavlovian paradigm. Vertical gratings were generated on an oscilloscope at a space-averaged luminance of 5 and 23 cd/m2. The CSF (contrast sensitivity as a function of grating spatial frequence) peaked at about 0.3 c/deg, falling off at lower and higher spatial frequencies. CSF's were fitted by double exponential functions that were used to calculate acuity and point-spread functions. Acuity, defined as the half-period of a just resolvable unity contrast grating, ranged in different fish from 13′ to 22′, the smaller value agreeing with the acuity predicted from the intercone separation. The central region of the derived point-spread function subtended about 1.6°, which is smaller than both the smallest ganglion cell receptive field centers, and the limit of full summation previously found for the light-adapted goldfish. © 1979.