Courtship behaviour reveals temporal regularity is a critical social cue in mouse communication

While animals navigating the real world face a barrage of sensory input, their brains evolved to perceptually compress multidimensional information by selectively extracting the features relevant for survival. Notably, communication signals supporting social interactions in several mammalian species consist of acoustically complex sequences of vocalisations. However, little is known about what information listeners extract from such time-varying sensory streams. Here, we utilise female mice’s natural behavioural response to male courtship songs to identify the relevant acoustic dimensions used in their social decisions. We found that females were highly sensitive to disruptions of song temporal regularity and preferentially approached playbacks of intact over rhythmically irregular versions of male songs. In contrast, female behaviour was invariant to manipulations affecting the songs’ sequential organisation or the spectro-temporal structure of individual syllables. The results reveal temporal regularity as a key acoustic cue extracted by mammalian listeners from complex vocal sequences during goal-directed social behaviour

Host location in a specialist parasitoid wasp via olfactory cues – a physiological, behavioural and morphological study

For successful host location, parasitoids are thought to have evolved different strategies to filter relevant olfactory cues which indicate the presence of the host. Because of their versatility in their ecology and behaviour, as well as their fine tuned olfactory system to volatile compounds of the host and host plant, they have gained increasing recognition as model organisms to study learning and behaviour in an adaptive ecological context. However, neural and cellular mechanisms of olfactory detection and processing in parasitoids are mainly unknown.In this thesis physiological, behavioural and morphological experiments were used to determine neural and behavioural mechanisms of host location via olfactory cues in the specialist parasitoid Cotesia vestalis. C. vestalis showed significant antennal responses to a range of odour compounds. Behavioural experiments, however, have demonstrated that only the herbivore-induced plant volatile linalool attracts C. vestalis males and females, but 1-nonanol has a repulsive effect on females. A morphological study of the antennal lobe, the first brain area where olfactory information is processed, revealed 40 ordinary glomeruli in both males and females. In addition, a complex of 2-3 enlarged glomeruli (MGC) was found in males. The courtship behaviour observed in males and the MGC suggest that males could use sex pheromones to locate females. Finally, calcium imaging studies showed glomerular activity to olfactory stimulation in bees but not in parasitoids. In conclusion, the degree of host specialisation in C. vestalis appears to influence olfactory learning in males and females, which favours learning of volatiles related to its host and host plant, as well as the morphological organisation of the antennal lobe. Larger, fewer and possibly specialised glomeruli could enhance processing of odour cues which are important for this parasitoid

Whistle while you work it : the role of energetic state and audience identity in singing mouse vocal effort

Elaborate animal displays serve crucial functions as animals attempt to deploy displays precisely to maximize reproductive rewards and minimize potential costs. These costs include both the potential wasted resources from a failed display and the possibility that a display might evoke attack from a rival or predator. To achieve this, individuals must integrate both internal and external information before deciding whether to signal and how much energy to invest into a given signal. Here we examine display effort in Alston’s singing mouse, Scotinomys teguina. using leptin, a hormone secreted by adipose tissue that regulates energy allocation. We manipulated individual perception of energy balance through intraperitoneal injection of exogenous leptin and social context through playback of conspecific song. Leptin-injected mice responded with song to playback more frequently and quickly than saline-injected controls. Although leptin promoted increased song effort, we found that leptin also reduced song duration. Playback of conspecific songs also increased song effort. We next focused on social context by recording focal males when alone, in the presence of a familiar female mouse, with an unfamiliar female mouse, and with an unfamiliar male mouse. Singing mice produce two distinctive types of songs: the long, well-studied advertisement song and a short “strophe” song that is disproportionately produced in the presence of females. Advertisement songs produced in the presence of females are quieter but longer than those produced in other treatments. These advertisement songs also contain enough information to identify individuals. Upon further analysis of recordings, we find that singing mice also produce short vocalizations that are similar to the ultrasonic vocalizations common in rodents. These are almost never found when alone and are vastly more common in female-directed treatments than in other treatments. A cluster analysis shows that they fall into four distinct types: peeps, sweeps, and warbles, plus the short “strophe” songs discussed previously. All are more commonly produced to female audiences than to other males, and all contain identity information similarly to advertisement songs.Ecology, Evolution and Behavio

Balancing expectations:Adaptive flexibility in mammalian circadian rhythms

Circadian rhythms are internally generated oscillations of approximately 24 hours that synchronize with the environments day-night cycle, which drive and modulate countless behavioural and physiological processes. In this thesis we use a novel behavioural work-for-food paradigm which allows to study how changes in energy balance cause a change in the temporal niche of mice, making them adopt a day-active activity pattern. We show and discuss data supporting a functional role of circadian flexibility; diurnal activity patterns requiring less energy versus remaining night-active - for burrowing small mammals in temperate climate. We build on this by showing the rearrangements in temporal niche are associated with plasticity in the direct light response (photic masking) and explore differences between male and female mice. Further we show data that neither the adrenals nor the Paraventricular thalamic Nucleus are essential for circadian niche adaptation whereas the central circadian clock located in the suprachiasmatic nucleus remains of vital importance, despite itself not appearing to change phase. The rigidity of the SCN-timing might be linked to its role in measuring daylength and guiding seasonal rhythms. Which processes make behavioural and physiological rhythms obtain a different phase angle to the SCN during simulated food shortage remains largely elusive. The work in this thesis provides a solid scientific basis to re-address circadian flexibility and it’s relation to energy balance in future studies. Gaining more insights in circadian rhythm flexibility might solve the poorly understood mechanisms behind metabolic risks associated with human shift-work and how to cope with circadian disruptions

How does the brain extract acoustic patterns? A behavioural and neural study

In complex auditory scenes the brain exploits statistical regularities to group sound elements into streams. Previous studies using tones that transition from being randomly drawn to regularly repeating, have highlighted a network of brain regions involved during this process of regularity detection, including auditory cortex (AC) and hippocampus (HPC; Barascud et al., 2016). In this thesis, I seek to understand how the neurons within AC and HPC detect and maintain a representation of deterministic acoustic regularity. I trained ferrets (n = 6) on a GO/NO-GO task to detect the transition from a random sequence of tones to a repeating pattern of tones, with increasing pattern lengths (3, 5 and 7). All animals performed significantly above chance, with longer reaction times and declining performance as the pattern length increased. During performance of the behavioural task, or passive listening, I recorded from primary and secondary fields of AC with multi-electrode arrays (behaving: n = 3), or AC and HPC using Neuropixels probes (behaving: n = 1; passive: n = 1). In the local field potential, I identified no differences in the evoked response between presentations of random or regular sequences. Instead, I observed significant increases in oscillatory power at the rate of the repeating pattern, and decreases at the tone presentation rate, during regularity. Neurons in AC, across the population, showed higher firing with more repetitions of the pattern and for shorter pattern lengths. Single-units within AC showed higher precision in their firing when responding to their best frequency during regularity. Neurons in AC and HPC both entrained to the pattern rate during presentation of the regular sequence when compared to the random sequence. Lastly, development of an optogenetic approach to inactivate AC in the ferret paves the way for future work to probe the causal involvement of these brain regions

The Effects of noise of Zebrafish (Danio rerio) memory

Abstract Ever since the start of the industrial revolution anthropogenic disturbances have increased in severity. Anthropogenic noise is one such example, which has deleterious effects on organisms in both terrestrial and aquatic habitats. The range of effects may vary from interruptions in behavioural functions such as communication, feeding, breeding, and prey-predator interactions to physiological alterations in hormones levels or even severe damages to internal organs. In this study, I investigated the effects of white noise on the cognitive performance of zebrafish (Danio rerio) and its possible mechanism of action, focusing on GABA neurotransmitter levels in the brain. To this end, adult zebrafish were exposed to four sound treatments: a medium intensity sound presented in either a regular and irregular pattern, or a high intensity sound presented with either a regular or irregular pattern for 30 min. Subsequently, alterations in cognitive performance were evaluated using a plus maze associative learning paradigm and novel object recognition paradigm. The first experiment results showed a significant drop in the total travelling distance in noise-exposed treatments compared to controls without supplementary noise. Moreover, in the noise treatments, there was a trend towards fewer visits to the target arm of the maze in comparison to the control group. Although the total time spent in the target arm among noise-exposed treatments was significantly different compared to control, only the High-Irregular treatment was significantly different from the Medium-Regular and High-Regular treatments. In the second test, no significant difference was observed in the total travelling distance except for Medium-Irregular and High-Irregular groups that showed reduced movement. Fish in the High-Irregular treatment had the lowest visiting frequency and accumulated time around the novel object, and the highest latency to visit the novel object, which can be an indicator of developing neophobia in this group. Furthermore, the High-Irregular treatment had a significant difference compared to other noise-exposed treatments. The noise intensity and predictability did not reveal a significant difference between treatments. However, slight changes were noticeable in some of the behavioural variables. Our results indicated that noise exposure can affect zebrafish performance, and different patterns of noise may result in different outcomes. However, whether these changes are the results of a direct effect of noise on memory requires more studies