Chromatic properties of interneurons in the optic lobes of the bee

SummaryNarrow band or monochromatic neurons were recorded in the medulla and lobula of the bee optic lobe. The spectral sensitivities of UV, blue and green units were similar to, but narrower than those of the corresponding receptors.Colour opponent cells were recorded in the proximal medulla and were predominantly UV excited and inhibited by blue and green. Green and blue excited neurons which were inhibited by UV were rarely found. All opponent cells showed a maximum sensitivity change in the violet region. The receptive fields of these neurons were homogeneous, each point being excited by the one wavelength and being inhibited by the other.Polychromatic neurons, i.e. those that showed clearly colour dependent responses in several wavelength regions but which showed a dominant response in only one wavelength range were recorded mainly in the lobula. Only UV or green dominated polychromatic cells were found. Their receptive fields show complex colour dependent substructures which are not concentrically arranged.Two neurons showed definite inputs from more than one colour channel but remain narrow band. These neurons respond best in the region of overlap of two receptors, i.e. bluish-green and violet.Colour opponency appears to play a major role in colour integration as in vertebrates, although no evidence supporting the combination of colour with spatial opponency was found.