Directional sensitivity in cat of collicular auditory neurons to FM sound

Directional sensitivity for FM sound was compared between two types of FM sound, a linear FM and a "Step" FM digitally synthesized to contain 28 steady short tones with half-overlap in time between every successive pair, simulating the formant transitions of speech. There seemed to be no difference in the response of the cat collicular neuron in directionality of the units for ascending vs descending frequencies. As far as we have examined, no FM-sensitive neurons were observed which were specifically responsive to particular FM components in a stimulus.