Brain-wide visual habituation networks in wild type and fmr1 zebrafish

Abstract

Habituation is a form of learning during which animals stop responding to repetitive stimuli, and deficits in habituation are characteristics of several psychiatric disorders. Due to the technical challenges of measuring brain activity comprehensively and at cellular resolution, the brain-wide networks mediating habituation are poorly understood. Here we report brainwide calcium imaging during visual learning in larval zebrafish as they habituate to repeated threatening loom stimuli. We show that different functional categories of loom-sensitive neurons are located in characteristic locations throughout the brain, and that both the functional properties of their networks and the resulting behavior can be modulated by stimulus saliency and timing. Using graph theory, we identify a principally visual circuit that habituates minimally, a moderately habituating midbrain population proposed to mediate the sensorimotor transformation, and downstream circuit elements responsible for higher order representations and the delivery of behavior. Zebrafish larvae carrying a mutation in the fmr1 gene have a systematic shift towards sustained premotor activity in this network, and show slower behavioral habituation. This represents the first description of a visual learning network across the brain at cellular resolution, and provides insights into the circuit-level changes that may occur in people with Fragile X syndrome and related psychiatric conditions.Habituation is a simple form of non-associative learning, characterized by a decrease in response after multiple presentations of a stimulus, that is conserved across much of the animal kingdom 1 . It allows animals to remain attentive to novel and ecologically relevant stimuli while minimizing their expenditure of energy on inputs that occur frequently without consequence. The strength and speed of habituation, and of recovery during periods without the stimulus, depend on the parameters of the stimulus and its repetitions (the intensity, frequency, and number of stimuli) 2,3 . Careful modulations of these stimulus properties have proven useful in exploring the relationships between repetitive stimuli and behavior, thereby providing clues about the underlying habituation circuitry 4-7 .Other work has addressed some of the molecular and cellular dynamics mediating habituation, including reductions in motor neurons' presynaptic vesicle release during shortterm habituation and processes involving protein syntheses for longer-term forms of habituation [8][9][10][11][12][13] . At the other end of the spectrum, fMRI studies in humans have revealed changes in activity for various brain regions during habituation [14][15][16] . The intervening scales, of regional circuits and brain-wide networks, cannot be addressed using targeted cellular techniques or traditional brain-wide approaches. These networks, and the ways in which they change during habituation, can only be addressed by observing activity in whole populations of neurons (up to and including the whole brain) at single-cell...

Broad frequency sensitivity and complex neural coding in the larval zebrafish auditory system

“…Zebrafish larvae, which provide unparalleled opportunities for the description of sensory circuits and networks [15–18], have thus far been reported to have a rudimentary auditory system [19, 20]. As a result, many of the circuit-level details of complex auditory processing in fish remain unexplored, and it remains unclear whether the larvae of any fish species extract complex properties from auditory stimuli to inform behavior [21–23].…”

“…To give a visual representation of the data, clusters were mapped back onto the brain using Unity™ which has been adapted into a data visualization system. An isosurface mesh of the zebrafish brain was generated from the Zbrain masks for the diencephalon, mesencephalon, rhombencephalon, telencephalon and eyes using ImageVis3D [17, 18]. The mesh was imported in Unity and overlaid to the ROIs.…”

Calcium Imaging and the Curse of Negativity

“…However, negative deviations from the fluorescence baselines have been observed, and assumptions of non-negativity may cause the omission or misinterpretation of GECI data from populations with such negative deviations (Galizia et al, 2010 ; Munch and Galizia, 2017 ; Favre-Bulle et al, 2018 ; Marquez-Legorreta et al, 2019 ; Zimmerman et al, 2019 ). With the slow rise and decay of GECI probes, on the order of hundreds of milliseconds, a long-term average firing rate above 1 Hz would be convolved as a high fluorescence baseline.…”

Calcium imaging and the curse of negativity

“…However, negative deviations from the fluorescence baselines have been observed, and these assumptions of non-negativity may bias the results and observation by excluding relevant responses that do not show the expected peaks of activity above baseline (Favre-Bulle, , Marquez-Legorreta, Constantin et al 2019, Zimmerman, Huey et al 2019. With the slow rise and decay of GECI probes, in the hundreds of milliseconds, a long-term average firing rate above 0.1Hz would be convolved as a constant fluorescence increase above baseline.…”