A simple coding procedure enhances a neuron's information capacity.

The contrast-response function of a class of first order interneurons in the fly's compound eye approximates to the cumulative probability distribution of contrast levels in natural scenes. Elementary information theory shows that this matching enables the neurons to encode contrast fluctuations most efficiently.

Single photon signals in fly photoreceptors and first order interneurones at behavioral threshold.

1. The contrast sensitivity of the optomotor response of the fly Musca domestica was measured using a moving sinusoidal grating as the stimulus. In parallel experiments intracellular recordings were made from photoreceptors and first order visual interneurones to to determine their responses to the same threshold stimuli.

Effects of three syllable durations using the melodic intonation therapy technique.

Five nonfluent aphasics were presented English phrases with three syllable durations; a regular speech, non-intoned duration less than 1 sec per syllable, and two modified Melodic Intonation Therapy (MIT) intoned durations of 1.5 sec per syllable and 2.0 sec per syllable.

The structures of dorsal and ventral regions of a dragonfly retina.

The apposition eyes of the corduliid dragonfly Hemicordulia tau are each divided by pigment colour, facet size and facet arrangement into three regions: dorsal, ventral, and a posterior larval strip. Each ommatidium has two primary pigment cells, twenty-five secondary pigment cells, and eight receptor cells, all surrounded by tracheae which probably prevent light passing between ommatidia, and reduce the weight of the eye. Electron microscopy reveals that the receptor cells are of two types: small vestigial cells making virtually no contribution to the rhabdom, and full-size typical cells.

Receptor and interneuron light-adaptation in the dragonfly visual system.

Intracellular recordings show that the receptors and second-order interneurons of the dragonfly compound eye change their sensitivity in response to maintained illumination. Comparison of receptor with interneuron shows that neural mechanisms act to ensure that the modulation of interneuron membrane potential that is set up by contrast changes is independent of background intensity.