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

The cerebellum of the mormyrid fish consists of three major divisions: the valvula, the central lobes, and the caudal lobes. Several studies have focused on the central lobes and the valvula, but little is known about the caudal lobes. The mormyrid caudal lobe includes anterior and posterior components. The anterior caudal lobe is associated with the lateral line and eighth nerve end organs, whereas the posterior caudal lobe is associated with the electrosensory system. The present study examines the physiology and pharmacology of morphologically identified Purkinje cells and efferent cells in an in vitro slice preparation of the posterior caudal lobe. We found that the Purkinje cells in the posterior caudal lobe can be classified into three subtypes based on both their morphology and on their physiological responses to intracellular current injection and to synaptic inputs from parallel fibers and climbing fibers. Similarities and differences between the physiology of the caudal lobe and that of other regions of the mormyrid cerebellum and the mammalian cerebellum are discussed.

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Recurrent Feedback in the Mormyrid Electrosensory System: Cells of the Preeminential and Lateral Toral Nuclei

Journal of Neurophysiology ◽

10.1152/jn.01055.2004 ◽

2005 ◽

Vol 93 (4) ◽

pp. 2090-2103 ◽

Cited By ~ 7

Author(s):

Nathaniel B. Sawtell ◽

Claudia Mohr ◽

Curtis C. Bell

Keyword(s):

Electric Organ Discharge ◽

Electric Organ ◽

Motor Command ◽

Cell Types ◽

Electrosensory System ◽

Mormyrid Fish ◽

Descending Input ◽

Initial Description ◽

Electrosensory Processing ◽

Direct Feedback

Many sensory regions integrate information ascending from peripheral receptors with descending inputs from other central structures. However, the significance of these descending inputs remains poorly understood. Descending inputs are prominent in the electrosensory system of mormyrid fish and include both recurrent connections from higher to lower stages of electrosensory processing and electric organ corollary discharge (EOCD) signals associated with the motor command that drives the electric organ discharge. The preeminential nucleus (PE) occupies a key position in a feedback loop that returns information from higher stages of electrosensory processing to the initial stage of processing in the electrosensory lobe (ELL). This feedback reflects the integration of ascending electrosensory input from ELL, descending input from the lateral toral nucleus (torus), and EOCD inputs to PE. We used intracellular recording and axonal tracing of stained cells to characterize EOCD and electrosensory responses of several cell types in PE and the torus. PE and toral cells exhibit prominent EOCD responses that are not due to EOCD inputs from ELL. PE cells giving rise to a direct feedback projection to ELL respond to electrosensory stimuli with rapid, precisely timed spikes that will affect ELL neurons early during the same EOD cycle. EOCD and electrosensory responses in toral cells are similar to those observed in PE and may be important in shaping feedback to ELL. These results provide an initial description of electrosensory feedback to ELL as well as information about how ascending, descending, and EOCD inputs are combined at higher stages of electrosensory processing.

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Neural Readout of a Latency Code in the Active Electrosensory System

10.1101/2021.12.14.472594 ◽

2021 ◽

Author(s):

Nathaniel B Sawtell ◽

Krista Perks

Keyword(s):

Sensory Information ◽

Granular Cell ◽

Nerve Fibers ◽

Spike Count ◽

Stimulus Amplitude ◽

Electrosensory System ◽

Afferent Nerve Fibers ◽

Mormyrid Fish ◽

Sensory Responses ◽

Spike Latency

The latency of spikes relative to a stimulus conveys sensory information across modalities. However, in most cases it remains unclear whether and how such latency codes are utilized by postsynaptic neurons. In the active electrosensory system of mormyrid fish, a latency code for stimulus amplitude in electroreceptor afferent nerve fibers (EAs) is hypothesized to be read out by a central reference provided by motor corollary discharge (CD). Here we demonstrate that CD enhances sensory responses in postsynaptic granular cells of the electrosensory lobe, but is not required for reading out EA input. Instead, diverse latency and spike count tuning across the EA population gives rise to graded information about stimulus amplitude that can be read out by standard integration of converging excitatory synaptic inputs. Inhibitory control over the temporal window of integration renders two granular cell subclasses differentially sensitive to information derived from relative spike latency versus spike count.

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

eLife ◽

10.7554/elife.16851 ◽

2016 ◽

Vol 5 ◽

Cited By ~ 9

Author(s):

Alejandro Vélez ◽

Bruce A Carlson

Keyword(s):

Electric Fish ◽

Frequency Tuning ◽

Weakly Electric Fish ◽

Sensory Coding ◽

Electrosensory System ◽

Mormyrid Fish ◽

Intrinsic Oscillation ◽

Oscillation Frequencies ◽

Weakly Electric ◽

Peripheral Sensory

Recently, we reported evidence for a novel mechanism of peripheral sensory coding based on oscillatory synchrony. Spontaneously oscillating electroreceptors in weakly electric fish (Mormyridae) respond to electrosensory stimuli with a phase reset that results in transient synchrony across the receptor population (<xref ref-type="bibr" rid="bib5">Baker et al., 2015</xref>). Here, we asked whether the central electrosensory system actually detects the occurrence of synchronous oscillations among receptors. We found that electrosensory stimulation elicited evoked potentials in the midbrain exterolateral nucleus at a short latency following receptor synchronization. Frequency tuning in the midbrain resembled peripheral frequency tuning, which matches the intrinsic oscillation frequencies of the receptors. These frequencies are lower than those in individual conspecific signals, and instead match those found in collective signals produced by groups of conspecifics. Our results provide further support for a novel mechanism for sensory coding based on the detection of oscillatory synchrony among peripheral receptors.

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