Toward Naturalistic Neuroscience of Navigation: Opportunities in Coral Reef Fish

The neural substrate of navigation using hydrostatic cues in goldfish

Hydrostatic pressure is a global sensory cue exploited by fish to navigate in the vertical dimension. Unlike other navigational cues in the horizontal plane that usually require learning and memory to determine location, hydrostatic pressure signals the absolute position along the vertical axis. Recently, it was shown that fish can use hydrostatic signals to navigate. It remains unclear, however, which brain regions are involved in processing this signal. Here, we tested whether the dorsomedial and lateral parts of the pallium, two regions that were found to be critical in horizontal navigation, are also critical for hydrostatic cue detection in goldfish. The results show that lesions to both these regions cause fish performance to deteriorate to chance values, indicating that both regions play an important role in processing hydrostatic pressure cues. These findings thus contribute to the rapidly growing body of knowledge on teleost navigation in space.

The archerfish uses motor adaptation in shooting to correct for changing physical conditions

The archerfish is unique in its ability to hunt by shooting a jet of water from its mouth that hits insects situated above the water's surface. To aim accurately, the fish needs to overcome physical factors including changes in light refraction at the air-water interface. Nevertheless, archerfish can still hit the target with a high success rate under changing conditions. One possible explanation for this extraordinary ability is that it is learned by trial and error through a motor adaptation process. We tested this possibility by characterizing the ability of the archerfish to adapt to perturbations in the environment to make appropriate adjustments to its shots. We introduced a perturbing airflow above the water tank of the archerfish trained to shoot at a target. For each trial shot, we measured the error, i.e., the distance between the center of the target and the center of the water jet produced by the fish. Immediately after the airflow perturbation, there was an increase in shot error. Then, over the course of several trials, the error was reduced and eventually plateaued. After the removal of the perturbation, there was an aftereffect, where the error was in the opposite direction but washed out after several trials. These results indicate that archerfish can adapt to the airflow perturbation. Testing the fish with two opposite airflow directions indicated that adaptation took place within an egocentric frame of reference. These results thus suggest that the archerfish is capable of motor adaptation, as indicated by data showing that the fish produced motor commands that anticipated the perturbation.

A perspective on neuroethology: what the past teaches us about the future of neuroethology

For 100 years, the Journal of Comparative Physiology-A has significantly supported research in the field of neuroethology. The celebration of the journal's centennial is a great time point to appreciate the recent progress in neuroethology and to discuss possible avenues of the field. Animal behavior is the main source of inspiration for neuroethologists. This is illustrated by the huge diversity of investigated behaviors and species. To explain behavior at a mechanistic level, neuroethologists combine neuroscientific approaches with sophisticated behavioral analysis. The rapid technological progress in neuroscience makes neuroethology a highly dynamic and exciting field of research. To summarize the recent scientific progress in neuroethology, I went through all abstracts of the last six International Congresses for Neuroethology (ICNs 2010-2022) and categorized them based on the sensory modalities, experimental model species, and research topics. This highlights the diversity of neuroethology and gives us a perspective on the field's scientific future. At the end, I highlight three research topics that may, among others, influence the future of neuroethology. I hope that sharing my roots may inspire other scientists to follow neuroethological approaches.

Lateral and medial telencephalic pallium lesions impair spatial memory in goldfish

Fish, like many other animals, navigate to ensure survival. While the telencephalon region of the teleost fish brain is believed to play a critical role in navigation, lesion and electrophysiology studies differ as to whether navigation is situated in the lateral pallium or the medial pallium. To address this inconsistency, we replicated combined behavioral and lesion studies in the goldfish. Goldfish were trained in two navigation tasks testing allocentric navigation on a horizontal plus-maze and a horizontal breadboard to get a reward. The fish were divided randomly into lateral pallium lesion, medial pallium lesion, and sham groups and retested for their success rates. The lateral lesion group had a significant decrease of success on the breadboard task but not on the plus-maze task, whereas the medial lesion affected both tasks significantly. These results suggest that both the medial and lateral pallium are essential for the coding of spatial memory and challenge the assumption that one distinct region of the pallium is involved in spatial memory in teleost.