Characterisation of sensitivity and orientation tuning for visually responsive ensembles in the zebrafish tectum

Abstract

Sensory coding relies on ensembles of co-active neurons, but these ensembles change from trial to trial of the same stimulus. This is due in part to wide variability in the responsiveness of neurons within these ensembles, with some neurons responding regularly to a stimulus while others respond inconsistently. The specific functional properties that cause neurons to respond more or less consistently have not been thoroughly explored. Here, we have examined neuronal ensembles in the zebrafish tectum responsive to repeated presentations of a visual stimulus, and have explored how these populations change when the orientation or brightness of the stimulus is altered. We found a continuum of response probabilities across the neurons in the visual ensembles, with the most responsive neurons focused toward the spatial centre of the ensemble. As the visual stimulus was made dimmer, these neurons remained active, suggesting higher overall responsiveness. However, these cells appeared to represent the most consistent end of a continuum, rather than a functionally distinct “core” of highly responsive neurons. Reliably responsive cells were broadly tuned to a range of stimulus orientations suggesting that, at least for this stimulus property, tight stimulus tuning was not responsible for their consistent responses.

A profile of auditory‐responsive neurons in the larval zebrafish brain

“…Interestingly, we find that auditory responsive neurons are highly consistent, responding in nearly 100% of trials to their relevant stimuli. This stands in contrast to sensory coding in the visual system of larval zebrafish, where a wide range of response probabilities exist, and where different neurons show sharply different stimulus tuning (Bianco & Engert, ; Del Bene et al, ; Orger, Smear, Anstis, & Baier, ; Temizer et al, ; Thompson & Scott, ; Thompson et al, ). This is likely a function of the depth of sensory discrimination across these modalities.…”

“…Stimuli were generated in Audacity, RRID: SCR_007198. Imaging was performed on a house‐built SPIM microscope, as previously described (Thompson & Scott, ; Thompson et al, ). The essential components of this microscope are listed in Table .…”

Diffuse light‐sheet microscopy for stripe‐free calcium imaging of neural populations

“…Automatically identifying regions of interest roughly corresponding to individual neurons, a process referred to as segmentation, is an important step in describing activity across populations of neurons . To gauge the impacts of stripes on segmentation, we used the MorphoLibJ segmentation tool in FIJI , a widely used approach for segmenting based on the neurons' morphology .…”

Cellular resolution imaging of vestibular processing across the larval zebrafish brain

“…The introduction of genetically encoded calcium indicators (GECIs) has allowed the observation of activity across large populations of neurons with single-cell resolution, using fluorescence techniques such as 2-photon or selective plane illumination microscopy (SPIM). For sensory modalities that are readily compatible with stationary preparations, such as olfaction[13], audition[14-16], and especially vision[17-20], such studies have uncovered patterns of activity spanning thousands of neurons, in some cases encompassing the entire brain.…”