Nonlinear Transient Responses from Light-Adapted Wolf Spider Eyes to Changes in Background Illumination

Retinal action potentials were recorded at the corneas of light-adapted wolf spider eyes in response to large positive and negative step changes in background illumination. These incremental responses were superimposed upon the steady-state DC responses to the background illumination. Both positive and negative step responses had peaks which overshot the DC levels to which they decayed. The overshoot was greater for positive than for negative steps. Short term DC responses measured after one-half sec were larger for negative than for positive steps; these short-term DC responses were thus asymmetrical. However, responses to short positive and negative flashes were not asymmetrical; rather, they varied linearly with flash amplitude. Asymmetries were thus delayed in onset. The short-term DC responses were found to be different from the steady-state DC responses to maintained changes in background illumination. There was an approximately exponential decay or creep from the short-term to the steady-state DC responses. It is proposed that the dynamics of delayed asymmetries can explain the waveforms of the short-term transient responses.