Abstract
For many species, hunting is an innate behaviour that is crucial for survival, yet the circuits that control predatory action sequences are poorly understood. We used larval zebrafish to identify a population of pretectal neurons that control hunting. By combining calcium imaging with a virtual hunting assay, we identified a discrete pretectal region that is selectively active when animals initiate hunting. Targeted genetic labelling allowed us to examine the function and morphology of individual cells and identify two classes of pretectal neuron that project to ipsilateral optic tectum or the contralateral tegmentum. Optogenetic stimulation of single neurons of either class was able to induce sustained hunting sequences, in the absence of prey. Furthermore, laser ablation of these neurons impaired prey-catching and prevented induction of hunting by optogenetic stimulation of the anterior-ventral tectum. We propose that this specific population of pretectal neurons functions as a command system to induce predatory behaviour.
Highlights
In response to sensory information and internal states, animals select specific actions from a repertoire of options and produce adaptive behavioural programmes
Transgenic elavl3:H2BGCaMP6s;atoh7:gapRFP larvae (6–7 dpf, N = 8) were partially restrained in agarose gel, but with their eyes and tail free to move, and were presented with a range of visual cues including small moving prey-like spots, which evoke naturalistic hunting responses (Figure 1B) (Bianco et al, 2011; Bianco and Engert, 2015)
We found that the KalTA4u508 cells that could evoke hunting behaviour belonged to the projection classes that innervated the ipsilateral optic tectum (9/23 cells, hereafter abbreviatedipsi-projecting) or that belong to the presumptive accessory pretectal nucleus (APN) and connect to the contralateral tegmentum (14/23 cells, `contra-projecting; Figure 3G,H)
Summary
In response to sensory information and internal states, animals select specific actions from a repertoire of options and produce adaptive behavioural programmes. In various species, hunting responses can be evoked by prey-like stimuli, defined by specific conjunctions of sensory features (Ewert, 1997; Anjum et al, 2006; Bianco and Engert, 2015), and predatory behaviour is modulated by internal state variables including associative learning and feeding drive (Ewert et al, 2001; Jordi et al, 2015). Electrical stimulation of brain regions, including the optic tectum, can evoke hunting actions (Ewert, 1970; Bels et al, 2012) and recent studies in rodents have identified circuits that motivate predatory behaviour (Han et al, 2017; Li et al, 2018; Park et al, 2018), neurons that command vertebrate hunting have yet to be identified
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