CALIFORNIA INST OF TECH PASADENA
Pagination or Media Count:
The properties of a model describing optomotor responses in the housefly are listed. Some of these theoretical properties may be found empirically by histological and electrophysiological techniques. The parameters required are the interommatidial angle, the diameter of the receptive field of an ommatidium or retinula cell, and the relationship between the generator potential and light intensity. The interommatidial angle was measured histologically. This is variable over the whole eye, the most uniform region lying between 20 and 60 degrees in the horizontal plane anterior 0 degrees and 30 degrees above and 10 degrees below horizontal in the vertical. The mean interommatidial angle in the horizontal plane is 3.9 degrees, and 2.5 degrees in the vertical. The role of screening pigment is examined. This is most dense in the upper part of the eye. During dark adaptation the pigment migrates, moving inwards away from the lenses and contracting outwards towards the pseudocone from deeper parts of the retina. This is discussed in relation to the optical system of the ommatidia, and it is suggested that the pigment migration will lead to a widening of the receptive field.