Arctiid moths and bat echolocation: broad-band clicks interfere with neural responses to auditory stimuli in the nuclei of the lateral lemniscus of the big brown bat.

Clicks emitted by arctiid moths interfere with the ranging ability of echolocating bats. To identify possible neural correlates of this interference, we recorded responses of single units in the nuclei of the lateral lemniscus to combinations of a broad-band click and a test signal (pure tones or frequency-modulated sweeps). In 77% of 87 units tested, clicks interfered with neural responses to the test stimuli. The interference fell into two categories: latency ambiguity and suppression. Units showing latency ambiguity responded to both the click and the test signal. However, when the click occurred within a window of approximately 3 ms before the onset of the test signal, the latency of the response to the test signal was affected. Units that were suppressed did not respond to clicks. Nevertheless, when a click was presented immediately before or simultaneously with a test signal, the response to the test signal was eliminated. Both types of units were found throughout the lateral lemniscus except for the columnar division of the ventral nucleus, where all units tested exhibited latency ambiguity. There is a close match between the single unit data and previous studies of range difference discrimination in the presence of clicks.