Motivated state control in larval zebrafish: behavioral paradigms and anatomical substrates

Abstract

Over the course of each day, animals prioritize different objectives. Immediate goals may reflect fluctuating internal homeostatic demands, prompting individuals to seek out energy supplies or warmth. At other times, the environment may present temporary challenges or opportunities. Homeostatic demands and environmental signals often elicit persistent changes in an animal’s behavior to meet needs and challenges over extended periods of time. These changes reflect the underlying motivational state of the animal. The larval zebrafish has been established as an effective genetically tractable vertebrate system to study neural circuits for sensory-motor reflexes. Fewer studies have exploited zebrafish to study brain circuits that control motivated behavior. In part this is because appropriate conceptual frameworks, anatomical knowledge, and behavioral paradigms are not yet well established. This review sketches a general conceptual framework for studying motivated state control in animal models, how this applies to larval zebrafish and the current knowledge on neuroanatomical substrates for state control in this model.

Search strategy is regulated by somatostatin signaling and deep brain photoreceptors in zebrafish

“…As for other short-term internal states, search behaviors are typically time-limited and reversible [ 10 ]. If a resource is not located within the local environment, a roaming search strategy is often initiated, which is characterized by an outward movement profile [ 36 , 37 ].…”

“…Motivated behaviors such as search-states are goal directed, in that they promote specific objectives [ 10 , 38 , 39 ]. Therefore, to rigorously test whether local and outward movement patterns facilitate light-search behavior, we developed two novel phototaxis assays.…”

“…Search behavior requires the maintenance of an internal state that appropriately regulates motor activity, and potentially also modulates sensory thresholds to facilitate the discovery of desirable resources [ 18 , 19 ]. Short-term internal states such as arousal and hunger, and movement profiles consistent with exploratory behavior are present in larval stage zebrafish [ 10 , 11 , 20 – 22 ], raising the possibility that autogenic search behavior has also developed.…”

An Afferent Neuropeptide System Transmits Mechanosensory Signals Triggering Sensitization and Arousal in C. elegans

“…Hallmarks of arousal include sensitization in the form of enhanced sensory acuity, increased motor activity, and greater reactivity to external stimuli. Arousal is a highly conserved, possibly universal feature of animal nervous systems ( Horstick et al., 2016 , Pfaff et al., 2008 ) and is thought to provide a crucial mechanism through which animals can respond appropriately to their environment. Arousal can be “endogenously generated”; for example, the sleep-wake cycle leads to periods of hyperactive motion and increased neural activity alternating with quiescent periods with lower or altered patterns of neural activity ( Chiu et al., 2016 , Iannacone et al., 2017 , Lebestky et al., 2009 , Turek et al., 2016 ).…”

Impairment of motor but not anxiety‐like behavior caused by the increase of dopamine during development is sustained in zebrafish larvae at later stages

“…In this study, we performed a more detailed analysis and observed an overall diminishment of motor behavior in DA‐treated larvae in both the 5‐min and 30‐min analyses (Figure ). In our previous study, we showed a decrease in the number of GABAergic neurons within the 5 dpf DA‐treated larvae pallium and subpallium, which are regions suggested to be related to motivational states; as well as the pretectum and optic tectum, which are regions suggested to be related to vision (Gahtan, ; Horstick, Mueller, & Burgess, ). Moreover, we observed an increase in the number of GABAergic neurons in the thalamus, which is suggested to be a sensory relay station (Mueller, ).…”