Sj. Judge et Fc. Rind, THE LOCUST DCMD, A MOVEMENT-DETECTING NEURON TIGHTLY TUNED TO COLLISION TRAJECTORIES, Journal of Experimental Biology, 200(16), 1997, pp. 2209-2216
A Silicon Graphics computer was used to challenge the locust descendin
g contralateral movement detector (DCMD) neurone with images of approa
ching objects. The DCMD gave its strongest response, measured as eithe
r total spike number or spike frequency, to objects approaching on a d
irect collision course. Deviation in either a horizontal or vertical d
irection from a direct collision course resulted in a reduced response
, The decline in the DCMD response with increasing deviation from a co
llision course was used as a measure of the tightness of DCMD tuning f
or collision trajectories. Tuning was defined as the half-width of the
response when it had fallen to half its maximum level. The response t
uning, measured as averaged mean spike number versus deviation away fr
om a collision course, had a halfwidth at half-maximum response of 2.4
degrees-3.0 degrees for a deviation in the horizontal direction and 3
.0 degrees for a deviation in the vertical direction. Mean peak spike
frequency showed an even sharper tuning, with a halfwidth at half-maxi
mum response of 1.8 degrees for deviations away from a collision cours
e in the horizontal plane.