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Detection of transient synchrony across oscillating receptors by the central electrosensory system of mormyrid fish

  1. Alejandro Vélez  Is a corresponding author
  2. Bruce A Carlson  Is a corresponding author
  1. Washington University in St. Louis, United States
Research Advance
Cite this article as: eLife 2016;5:e16851 doi: 10.7554/eLife.16851
4 figures and 1 data set

Figures

The central electrosensory system detects transient synchrony among oscillating receptors.

50 µm horizontal sections of the midbrain of P. tenuicauda (A), P. microphthalmus (B), and B. niger (C). The midbrain exterolateral nucleus (EL) in P. tenuicauda is small and undifferentiated; in the other two species, EL is enlarged and subdivided into separate anterior (ELa) and posterior (ELp) nuclei. (D) Representative mean evoked potentials (n = 10 traces) from the EL of P. tenuicauda obtained from relatively more anterior (left) and posterior (right) regions. Representative mean evoked potentials (n = 10 traces) obtained from ELa (left) and ELp (right) in P. microphthalmus (E) and B. niger (F). Scale bars in (A), (B), and (C) represent 200 µm. L, lateral nucleus; OT, optic tectum; MD, mediodorsal nucleus; Val, valvula cerebellum.

https://doi.org/10.7554/eLife.16851.002
Evoked potentials in the midbrain are blocked by a corollary discharge of the EOD motor command.

Effect of stimulus delay with respect to the spinal EOD motor command on the amplitude of evoked potentials in P. tenuicauda (A), P. microphthalmus (B) and B. niger (C). Evoked potentials in P. tenuicauda were obtained throughout EL, in locations varying from more anterior to more posterior, as in (i) and (ii) in Figure 1A. In (B) and (C), full symbols represent data from the anterior division of the exterolateral nucleus (ELa) and open symbols represent data from the posterior division (ELp). We measured the peak-to-peak amplitude of the evoked potential at each latency and normalized them to the maximum value for each fish tested and at each nucleus. Traces on the right are representative mean evoked potentials (n = 10 traces) when the stimulus was delivered at delays of 0, 1, 2, 2.5, 3, 3.5, 4, 5, and 6 ms with respect to the EOD command. Each symbol in (A), (B), and (C) represent the mean normalized amplitude and the error bars represent the S.E.M.

https://doi.org/10.7554/eLife.16851.003
Frequency content relates to the duration of communication signals in pulse-type mormyrids.

(A) Power spectra and (B) representative waveforms of electric organ discharges (EODs) of the three species tested.

https://doi.org/10.7554/eLife.16851.004
Midbrain frequency sensitivity matches EOD frequency content in species with spiking receptors, but not in species with oscillating receptors.

(A) Representative mean evoked potentials (n = 10 traces) from the EL of P. tenuicauda (black), ELa of P. microphthalmus (blue), and ELa of B. niger (red) in response to single-cycle bipolar sinusoidal pulses with durations of 0.5ms (left) and 0.1 ms (right), which correspond to peak power frequencies of 1.7 and 8.4 kHz, respectively. Frequency tuning curves of the midbrain exterolateral nucleus (EL) in P. tenuicauda (B), and the anterior (ELa) and posterior (ELp) subnuclei of EL in P. microphthalmus (C and D, respectively) and B. niger (E and F, respectively). Evoked potentials in P. tenuicauda were obtained throughout EL, in locations varying from more anterior to more posterior, as in (i) and (ii) in Figure 1A. Frequency tuning curves were obtained at three intensities: 73.6 (full lines), 23.4 (dashed lines), and 7.4 (dotted lines) mV/cm. We measured the peak-to-peak amplitude of the evoked potential at each frequency and intensity, and normalized them to the maximum value for each fish and each nucleus separately. Gray boxes represent the frequencies between the peak power frequency (ppf) of the conspecific EOD and one octave below the ppf. Each symbol in (B), (C), (D), (E), and (F) represent the mean normalized amplitude and the error bars represent the S.E.M.

https://doi.org/10.7554/eLife.16851.005

Data availability

The following data sets were generated
  1. 1

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