scholarly journals Disproportionate frequency representation in the inferior colliculus of doppler-compensating Greater Horseshoe bats: Evidence for an acoustic fovea

1979 ◽  
Vol 132 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Gerd Schuller ◽  
George Pollak
Keyword(s):  
Inferior Colliculus ◽  
Frequency Representation ◽  
Horseshoe Bats

scholarly journals Multiple sounds degrade the frequency representation in monkey inferior colliculus

2020 ◽  
Author(s):  
Shawn M. Willett ◽  
Jennifer M. Groh
Keyword(s):  
Maximum Likelihood ◽  
Firing Rate ◽  
Inferior Colliculus ◽  
Frequency Tuning ◽  
Tuning Curve ◽  
Response Functions ◽  
Tuning Curves ◽  
Frequency Representation ◽  
Simultaneous Sounds ◽  
Alternative Theories

AbstractHow we distinguish multiple simultaneous stimuli is uncertain, particularly given that such stimuli sometimes recruit largely overlapping populations of neurons. One hypothesis is that tuning curves might change to limit the number of stimuli driving any given neuron when multiple stimuli are present. To test this hypothesis, we recorded the activity of neurons in the inferior colliculus while monkeys localized either one or two simultaneous sounds differing in frequency. Although monkeys easily distinguished simultaneous sounds (∼90% correct performance), the frequency tuning of inferior colliculus neurons on dual sound trials did not improve in any obvious way. Frequency selectivity was degraded on dual sound trials compared to single sound trials: tuning curves broadened, and frequency accounted for less of the variance in firing rate. These tuning curve changes led a maximum-likelihood decoder to perform worse on dual sound trials than on single sound trials. These results fail to support the hypothesis that changes in frequency response functions serve to reduce the overlap in the representation of simultaneous sounds. Instead these results suggest alternative theories, such as recent evidence of alternations in firing rate between the rates corresponding to each of the two stimuli, offer a more promising approach.

Duration-Sensitive Neurons in the Inferior Colliculus of Horseshoe Bats: Adaptations for Using CF-FM Echolocation Pulses

2008 ◽  
Vol 99 (1) ◽  
pp. 284-296 ◽  
Author(s):  
Feng Luo ◽  
Walter Metzner ◽  
Feijian J. Wu ◽  
Shuyi Y. Zhang ◽  
Qicai C. Chen
Keyword(s):  
Inferior Colliculus ◽  
Stimulus Intensity ◽  
Signal Intensity ◽  
The Other ◽  
Pass Band ◽  
Constant Frequency ◽  
Sound Levels ◽  
Band Pass ◽  
Horseshoe Bat ◽  
Horseshoe Bats

The present study examines duration-sensitive neurons in the inferior colliculus (IC) of the least horseshoe bat, Rhinolophus pusillus, from China. In contrast to other bat species tested for duration selectivity so far, echolocation pulses emitted by horseshoe bats are generally longer and composed of a long constant-frequency (CF) component followed by a short downward frequency-modulated (FM) sweep (CF-FM pulse). We used combined CF-FM pulses to analyze the differential effects that these two pulse components had on the duration tuning in neurons of the horseshoe bat's IC. Consistent with results from other mammals, duration-sensitive neurons found in the least horseshoe bat fall into three main classes: short-pass, band-pass, and long-pass. Using a CF stimulus alone, 54% (51/95) of all IC neurons showed at least one form of duration selectivity at one or more stimulus intensities. In 65 of the 95 IC neurons tested with CF pulses, we were also able to test their duration selectivity for a combined CF-FM pulse, which increased the ratio of duration-sensitive neurons to 66% (43/65). Seven to 15 neurons that failed to show duration tuning for CF bursts became duration sensitive for CF-FM pulses, with most of them exhibiting short-pass (depending on stimulus intensity, between 4 and 8 neurons) or band-pass tuning (1–3 neurons). Increasing stimulus intensities did not affect the duration tuning in 53% (23/43) of duration-sensitive neurons for CF bursts and in about 26% (7/27) for CF-FM stimuli. In the remaining neurons, increasing sound levels generally reduced the ratio of duration-sensitive neurons to 33% for CF and 37% for CF-FM stimulation. In those that remained duration sensitive, louder CF bursts shortened best durations in band-pass neurons and cutoff durations in short- and long-pass neurons, whereas louder CF-FM stimuli reduced the cutoff durations only in short-pass neurons. Bandwidths of band-pass neurons were not significantly affected by any stimulus configuration, with only a slight trend for increasing bandwidths for louder CF bursts (but not CF-FM stimuli). Best durations and cutoff durations reached higher values than those in the other bat species examined so far and roughly match the longer durations of echolocation pulses emitted by horseshoe bats. Therefore presentation of a CF-FM stimulus improved the duration sensitivity in IC neurons by increasing the ratio of duration-tuned neurons and making them less susceptible to changes in signal intensity.

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