Biology subjects

Beetz, M. J.

Publications and source records attributed to Beetz, M. J..

8 recordsLinked to original sources

bioRxiv2025

Honeybees acquire a spatial memory by learning landmarks and visual patterns in parallel

Spatial memory is vital for central-place foragers that navigate the same habitat on a daily basis. Computational models suggest that insects remember panoramic snapshots to return to goal locations. To what extent these snapshots represent retinotopic images or whether salient landmarks are stored isolated from the panorama remains unclear. With a newly designed spatial-memory task, we show that honeybees employ two different strategies for learning visual cues. In essence, they learn visual patterns as panoramic snapshots and three-dimensional objects as single entities. Freely walking honeybees were challenged to locate a rewarded feeder in the presence of visual patterns or objects. Selectively perturbing the panorama degraded the orientation behaviour only when visual patterns were present but not when objects were available. Presenting visual patterns and objects simultaneously and setting these cues in conflict revealed that honeybees primarily rely on a landmark-based navigation strategy. Making the spatial information of the objects ambiguous did not induce disorientation because the honeybees then relied on the visual patterns for finding the feeder. Altogether, our results suggest two independent visual memories operating in parallel, one dedicated to local landmarks and a second one for visual patterns that could be interpreted as distal cues. Notably, in rats, the spatial tuning of some hippocampal cells has been shown to be either anchored to local or distal cues. Our results provide the first hints that a distinction between local and distal cues may also be present in the insect brain.

animal behavior and cognition↗

bioRxiv2022

Neural representation of goal direction in the monarch butterfly brain

Neural processing of a navigational goal requires the continuous comparison between the current heading and the intended goal direction. While the neural basis underlying the current heading is well-studied in insects, the coding of the goal direction is completely unexplored. Here, we identify for the first time neurons that encode goal direction in the brain of a navigating insect, the monarch butterfly. The spatial tuning of these neurons accurately correlates with the animals goal direction while being unaffected by compass perturbations. Thus, they specifically encode the goal direction similar to goal neurons described in the mammalian brain. Taken together, a navigation network based on goal-direction and heading-direction neurons generates steering commands that efficiently guides the monarch butterflies to their migratory goal.

neuroscience↗

bioRxiv2022

Weighting of celestial and terrestrial cues in the monarch butterfly central complex

Monarch butterflies rely on external cues for orientation during their annual long-distance migration from Northern US and Canada to Central Mexico. These external cues can be celestial cues, such as the sun or polarized light, which are processed in the internal compass of the brain, termed the central complex (CX). Previous research typically focused on how individual simulated celestial cues are encoded in the butterflys CX. However, in nature, the butterflies perceive several celestial cues at the same time and need to integrate them to effectively use the compound of all cues for orientation. In addition, a recent behavioral study revealed that monarch butterflies can rely on terrestrial cues, such as the panoramic skyline, for orientation and use them in combination with the sun to maintain a directed flight course. How the CX encodes a combination of celestial and terrestrial cues and how they are weighted in the butterflys CX is still unknown. Here, we examined how input neurons of the CX, termed TL neurons, combine celestial and terrestrial information. While recording intracellularly from the neurons, we presented a sun stimulus and polarized light to the butterflies as well as a simulated sun and a panoramic scene simultaneously. Our results show that celestial cues are integrated linearly in these cells, while the combination of the sun and a panoramic skyline did not always follow a linear integration of action potential rates. Interestingly, while the weighting between the sun and polarized light was invariant between individual input neurons, it varied strongly when the sun stimulus and the panoramic skyline were presented simultaneously. Taken together, this dynamic weighting between celestial and terrestrial cues may allow the butterflies to flexibly set their cue preference during navigation.

neuroscience↗

bioRxiv2021

State-dependent egocentric and allocentric heading representation in the monarch butterfly brain

For navigation, animals use a robust internal compass. Compass navigation is especially crucial for long-distance migrating animals like monarch butterflies, which use a sun compass to navigate every fall over 4,000 km to their overwintering sites. The central complex, a brain region equipped with sun-compass neurons, is proposed to control the butterflys heading. Although the activity of central-complex neurons exhibits a locomotor-dependent modulation in many insects, the consequences of such modulations for the coding of heading remain unexplored. Here, we developed tetrode recordings from tethered flying monarch butterflies to reveal how flight modulates heading representation. We found that during flight, heading-direction neurons change their tuning, transforming the central-complex network to function as a global compass. This compass coding is characterized by the dominance of steering feedback and allows for robust heading representation even under unreliable visual scenarios, an ideal strategy for maintaining a migratory heading over enormous distances.

neuroscience↗

bioRxiv2020

Spatial orientation based on multiple visual cues in monarch butterflies

Monarch butterflies (Danaus plexippus) are prominent for their annual long-distance migration from North America to its overwintering area in Central Mexico. To find their way on this long journey, they use a sun compass as their main orientation reference but will also adjust their migratory direction with respect to mountain ranges. This indicates that the migratory butterflies also attend to the panorama to guide their travels. Here we studied if non-migrating butterflies - that stay in a more restricted area to feed and breed - also use a similar compass system to guide their flights. Performing behavioral experiments on tethered flying butterflies in an indoor LED flight simulator, we found that the monarchs fly along straight tracks with respect to a simulated sun. When a panoramic skyline was presented as the only orientation cue, the butterflies maintained their flight direction only during short sequences suggesting that they potentially use it for flight stabilization. We further found that when we presented the two cues together, the butterflies register both cues in their compass. Taken together, we here show that non-migrating monarch butterflies can combine multiple visual cues for robust orientation, an ability that may also aid them during their migration. SummaryNon-migrating butterflies keep directed courses when viewing a simulated sun or panoramic scene. This suggest that they orient based on multiple visual cues independent of their migratory context.

animal behavior and cognition↗

bioRxiv2019

Superfast periodicities in distress vocalizations emitted by bats

Communication sounds are ubiquitous in the animal kingdom, where they play a role in advertising physiological states and/or socio-contextual scenarios. Distress sounds, for example, are typically uttered in distressful scenarios such as agonistic interactions. Here, we report on the occurrence of superfast temporal periodicities in distress calls emitted by bats (species Carollia perspicillata). Distress vocalizations uttered by this bat species are temporally modulated at frequencies close to 1.7 kHz, that is, [~]17 times faster than modulation rates observed in human screams. Fast temporal periodicities are represented in the bats brain by means of frequency following responses, and temporally periodic sounds are more effective in boosting the heart rate of awake bats than their demodulated versions. Altogether, our data suggest that bats, an animal group classically regarded as ultrasonic, can exploit the low frequency portion of the soundscape during distress calling to create spectro-temporally complex, arousing sounds.

animal behavior and cognition↗

bioRxiv2019

Dynamic adaptations in the echolocation behavior of bats in response to acoustic interference

Animals extract behaviorally relevant signals from "noisy" environments. To investigate signal extraction, echolocating provides a rich system testbed. For orientation, bats broadcast calls and assign each echo to the corresponding call. When orienting in acoustically enriched environments or when approaching targets, bats change their spectro-temporal call design. Thus, to assess call adjustments that are exclusively meant to facilitate signal extraction in "noisy" environments, it is necessary to control for distance-dependent call changes. By swinging bats in a pendulum, we tested the influence of acoustic playback on the echolocation behavior of Carollia perspicillata. This paradigm evokes reproducible orientation behavior and allows a precise definition of the influence of the acoustic context. Our results show that bats dynamically switch between different adaptations to cope with sound-based navigation in acoustically contaminated environments. These dynamics of echolocation behavior may explain the large variety of adaptations that have been reported in the bat literature. Summary statementThe frugivorous bat Carollia perspicillata dynamically switch between different adaptations when echolocating in acoustically contaminated environments.

animal behavior and cognition↗

bioRxiv2018

Adaptations in the echolocation behavior of fruit-eating bats when orienting under challenging conditions

Summary statementWhen echolocating under demanding conditions e.g. noisy, narrow space, or cluttered environments, frugivorous bats adapt their call pattern by increasing the call rate within biosonar groups.\n\nAbstractFor orientation, echolocating bats emit biosonar calls and use echoes arising from call reflections. They often pattern their calls into groups which increases the rate of sensory feedback over time. Insectivorous bats emit call groups at a higher rate when orienting in cluttered compared to uncluttered environments. Frugivorous bats increase the rate of call group emission when they echolocate in noisy environments. Here, calls emitted by conspecifics potentially interfere with the bats biosonar signals and complicate the echolocation behavior. To minimize the information loss followed by signal interference, bats may profit from a temporally increased sensory acquisition rate, as it is the case for the call groups. In frugivorous bats, it remains unclear if call group emission represents an exclusive adaptation to avoid interference by signals from other bats or if it represents an adaptation that allows to orient under demanding environmental conditions. Here, we compared the emission pattern of the frugivorous bat Carollia perspicillata when the bats were flying in noisy versus silent, narrow versus wide or cluttered versus non-cluttered corridors. According to our results, the bats emitted larger call groups and they increased the call rate within the call groups when navigating in narrow, cluttered, or noisy environments. Thus, call group emission represents an adaptive behavior when the bats orient in complex environments.

animal behavior and cognition↗