Spectral Sensitivity of Photoreceptors and Spectral Inputs to the Neurons of the First Optic Ganglion in the Locust (Locusta migratoria)

Abstract

Spectral characteristics of locust photoreceptors and second order neurons were studied by intracellular recordings. Three types of receptors were found in the retina: λ= 360,430 and 530 nm. 38 of 41 examined neurons had very wide spectral efficiency and spectral sensitivity curves with more than 50% of their maximal sensitivity in the range of 360–550 nm. Comparison of spectral characteristics of the receptors and neurons shows that the neurons receive inputs from three receptor types and integrate their signals. A number of cells were stained with Procion yellow. The stained cells were identified as large monopolar neurons. In addition, 3 neurons with narrow spectral sensitivity curves and peaks at 530 nm were found. Their spectral characteristics correspond to those of the photoreceptors with λ = 530 nm, therefore they have inputs only from this single receptor type.