No abstract

When solving navigational problems, remembering that a critical location is approaching can enable appropriate behavioural choices without waiting for sensory signals. Whereas multiple types of neuron in the hippocampus and retrohippocampal cortex represent locations using codes based on discrete spatial firing fields, analogue neural representations may be advantageous for efficiently recalling proximity to locations of behavioral importance. Here, we identify retrohippocampal neurons that use analogue ramp-like changes in firing rate to represent location as mice navigate a virtual environment in which they have learned the location of a reward. Ramp-like firing patterns had positive or negative slopes and could switch polarity or reset their rate at the reward location. These transitions were maintained when location cues were removed, indicating that path integration is sufficient to drive recall of the track structure expressed through ramp-like codes. We suggest that analogue ramp-like representations encode learned models for goal-directed navigation.

Grid firing fields of neurons in the medial entorhinal cortex have been proposed as a neural substrate for spatial localisation and path integration. While there are strong theoretical arguments to support these roles, it has been challenging to directly test whether and when grid cells contribute to behaviours. Here, we investigate firing of grid cells during a task in which mice obtain rewards by recalling a location on a linear virtual track. We find that grid firing can either be anchored to the track, providing a code for position, or can instead encode distance travelled independent from the track position. Because engagement of these representations varied between and within sessions we were able to test whether positional grid firing predicts behaviour. We find that when a visual cue indicates the reward location, performance is similar regardless of whether grid cells encode position or distance. By contrast, in the absence of the visual cue, performance was substantially improved when grid cells encoded position compared to when they encoded distance. Our results suggest that positional anchoring of grid firing enhances performance of tasks that require path integration.

Bottlenose dolphins ( Tursiops truncatus and Tursiops aduncus; BND) live in coastal waters, prompting frequent contact with humans. Interaction with BND can be either planned (e.g. swim-with-dolphin experiences) or chance (e.g. BND surfing on boat wakes). These charismatic cetaceans are common in many forms of wildlife tourism, including marine wildlife tours, swim-with-dolphin experiences and hand feeding. BND also interact with humans by chance during ocean recreation activities, such as surfing, swimming and boating. Within fisheries, there is both cooperation and conflict between humans and BND. Through a literature review, this paper highlights the effects such interactions cause to both BND and humans with a focus on wildlife tourism, ocean recreation and fisheries.