Fig 1.
The spectrogram of representative echolocation call of Hipposideros pratti (A) and CF-FM stimulus used in our present study (B). The echolocation call included 3 harmonics (H1-H3), and the CF component of these harmonics were 28.9 kHz (CF1), 58.9 kHz (CF2) and 88.5 kHz (CF3).
Fig 2.
Basic properties of the SO and DO neurons.
(A): SO and DO neurons. The PSTHs show the discharge pattern and number of impulses in the SO and DO neurons. Whereas both neurons discharged impulses to CF, FM and CF-FM sounds (Aa), only the DO neuron discharged impulses to the FM component of the CF-FM sound (Ab3). A sketch of each sound stimulus is shown below the abscissae. (B) and (C): Scatter plots of the distribution of BFs in relation to the recording depth of (B) SO and (C) DO neurons. The linear regression line is shown by a solid line. r is the correlation coefficient of the distribution. The grey rectangle indicates the frequency range of the bat’s second harmonic. (D): Average recording depth, (E): MT, and (F): BF of SO (solid bar) and DO (empty bar) neurons. # P >0.05.
Fig 3.
The iso-level frequency tuning curve (FTC) stimulated by CF sounds.
Iso-level FTC in (A) DO and (B) SO neurons; (a): representative HFN, (b): LFN, (c): BS, and (d): multi-peak. The number and percentage of each type of iso-level FTC are shown as n and %, respectively. The numbers in each figure represent the data number of each neuron; BF, BW, BWL, and BWH are shown in order from top to bottom.
Table 1.
The iso-level frequency tuning curve (FTC) types under CF and CF-FM stimulation of SO neurons.
Table 2.
The iso-level frequency tuning curve (FTC) types under CF and CF-FM stimulation of DO neurons.
Fig 4.
The BWs changes after switching the CF to CF-FM sounds.
(A): SO and (B) DO neurons. The BWs were (a) decreased, (b) increased, and (c) did not change, after switching the CF to CF-FM sounds. The number and percentage of each type of change are shown as n and %, respectively. The numbers in each figure represent the data number of each neuron; BF and BW under CF stimulation, BF and BW under CF-FM stimulation.
Fig 5.
BW distribution of SO and DO neurons.
Scatter plots showing the distribution of BWs under CF and CF-FM stimulation for (A) SO and (B) DO neurons. The solid line represents the equal-value diagonal line and the dashed line is the 0.5-kHz difference line. (C): Box plots show BWs under CF and CF-FM stimulation for SO and DO neurons. # P >0.05; * P <0.05.
Fig 6.
BW Change rate of SO and DO neurons.
The distribution of the BWs change rate against BF for (A) SO and (B) DO neurons. The solid line is the “zero line”, indicating that no change was observed in the BWs under CF and CF-FM stimulation; and the dashed line represents the 30% change rate line. (C): Mean BWs change rate of SO and DO neurons. (D): Mean BWs change rate of low BF SO and low BF DO neurons. LBF SO, low BF SO neurons; LBF DO, low BF DO neurons. * P <0.05.
Fig 7.
Scatter plots of BFs under CF and CF-FM stimulation for (A) SO and (B) DO neurons. The solid line represents the equal-value diagonal line and the dashed line is the 2-kHz difference line. The inset box plots show that the BFs under CF and CF-FM stimulation had no significant different between the SO (A inset) and the DO (B inset) neurons.
Fig 8.
Post-spike hyperpolarization latency (PSHL) and excitatory duration (ED) of SO and DO neurons.
(A) and (B): representative responses of (A) SO and (B) DO neurons to (a) CF and (b) CF-FM sounds. The number besides the action potential (AP) firing in each panel represents the total number of APs elicited by various stimuli per eight trials. The number after PSHL and ED in each panel is the average PSHL and ED value of each representative response. A sketch of each sound stimulus is shown below the neuron’s response. (C) and (D): Magnified view of the area highlighted with a dashed line rectangle in the corresponding response traces of (C) SO and (D) DO neurons. (E): comparisons of (a) PSHL and (b) ED under CF and CF-FM stimulation for SO and DO neurons. The PSHL under CF stimulation for SO and DO neurons were 14.2 ± 1.9 and 11.4 ± 1.3 ms; The PSHL under CF-FM stimulation for SO and DO neurons were 13.2 ± 1.8 and 10.9 ± 1.2 ms (Ea). The ED under CF stimulation for SO and DO neurons were 4.8 ± 1.1 and 2.3 ± 0.5 ms; The ED under CF-FM stimulation for SO and DO neurons were 3.9 ± 1.1 and 2.1 ± 0.6 ms (Eb). * P <0.05.