Delay-tuned neurons in the inferior colliculus of the mustached bat: implications for analyses of target distance.

Delay-tuned neurons in the inferior colliculus of the mustached bat: implications for analyses of target distance.

Portfors C V; Wenstrup J J

Journal of neurophysiology

1999

1999-09

We examined response properties of delay-tuned neurons in the central nucleus of the inferior colliculus (ICC) of the mustached bat. In the mustached bat, delay-tuned neurons respond best to the combination of the first-harmonic, frequency-modulated (FM1) sweep in the emitted pulse and a higher harmonic frequency-modulated (FM2, FM3 or FM4) component in returning echoes and are referred to as FM-FM neurons. We also examined H1-CF2 neurons. H1-CF2 neurons responded to simultaneous presentation of the first harmonic (H1) in the emitted pulse and the second constant frequency (CF2) component in returning echoes. These neurons served as a comparison as they are thought to encode different features of sonar targets than FM-FM neurons. Only 7% of our neurons (14/198) displayed a single excitatory tuning curve. The rest of the neurons (184) displayed complex responses to sounds in two separate frequency bands. The majority (51%, 101) of neurons were facilitated by the combination of specific components in the mustached bat's vocalizations. Twenty-five percent showed purely inhibitory interactions. The remaining neurons responded to two separate frequencies, without any facilitation or inhibition. FM-FM neurons (69) were facilitated by the FM1 component in the simulated pulse and a higher harmonic FM component in simulated echoes, provided the high-frequency signal was delayed the appropriate amount. The delay producing maximal facilitation ("best delay") among

Animal/physiology; Animals; Chiroptera/*physiology; Echolocation/*physiology; Inferior Colliculi/cytology/*physiology; Neural Inhibition/physiology; Neurons/*physiology; Reaction Time/physiology; Vocalization

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1326–1338

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