SPECTRAL SENSITIVITY OF THE GOLDFISH TORUS-LONGITUDINALIS

We measured the photopic spectral sensitivity of multiunit activity in the torus longitudinalis and optic tectum of goldfish. Since negative contrast stimuli are most effective for exciting torus longitudinalis , spiking activity was evoked by the shadow of a disc moving through a monochromatic light beam projected upon a screen. The amount of activ ity evoked in torus longitudinalis generally increased with the monoch romatic stimulus radiance at the same rate for all wavelengths, indica ting a univariant response. Spiking activity in tectum, however, incre ased at different rates across the spectrum, indicating color-dependen t responses. The action spectra for torus longitudinalis were all simi lar and relatively flat as expected of a homogeneous, broad-band lumin ance processing system, and about 1 log unit more sensitive than the t ectal action spectra. The latter generally displayed sharp peaks and d ips in sensitivity indicative of opponent processing.