C. Giovanni Galizia

• Prof.
• University of Konstanz

Olfactory coding relies on primary information from olfactory receptor cells that respond to volatile airborne substances. Despite extensive efforts, our understanding of odor‐response profiles across receptors is still poor, because of the vast number of possible ligands (odorants), the high sensitivity even to trace compounds (creating false posi...

Whether individuals exhibit consistent behavioural variation is a central question in the field of animal behaviour. This question is particularly interesting in the case of social animals, as their behaviour may be strongly modulated by the collective. In this study, we ask whether honeybees exhibit individual differences in stinging behaviour. We...

In insects, olfactory receptor neurons (ORNs) are localized in sensilla. Within a sensillum, different ORN types are typically co-localized and exhibit non-synaptic reciprocal inhibition through ephaptic coupling. This inhibition is hypothesized to aid odour source discrimination in environments where odor molecules (odorants) are dispersed by wind...

Groups of animals inhabit vastly different sensory worlds, or umwelten, which shape fundamental aspects of their behaviour. Yet the sensory ecology of species is rarely incorporated into the emerging field of collective behaviour, which studies the movements, population-level behaviours, and emergent properties of animal groups. Here, we review the...

Insect olfactory receptor neurons (ORNs) are often co-localized within sensilla and exhibit non-synaptic reciprocal inhibition through ephaptic coupling. It has been postulated that this inhibition aids odour source discrimination, as synchronous arrival of different odour molecules (odorants) from a single source should increase ephaptic inhibitio...

Sleep and sleep-like states are present across the animal kingdom, with recent studies convincingly demonstrating sleep-like states in arthropods, nematodes, and even cnidarians. However, the existence of different sleep phases across taxa is as yet unclear. In particular, the study of rapid eye movement (REM) sleep is still largely centered on ter...

Simple Summary Insects have several methods to protect themselves and their resources from danger. One of them is to use their sense of smell. In this review, we describe how insects use smell to detect threats and perform behaviours of ‘flight or fight’ such as avoidance, escape or attack, in order to protect themselves. We also discuss how group-...

The ground nesting raptor Montagu’s Harrier breeds in loose colonies in cereal fields in the Spanish Extremadura. It is unclear how and whether birds in different colonies interact and how harriers spend time before and after nesting, before starting migration. We used GPS–GSM tags deployed on ten females and three males, some over multiple seasons...

An effective means of finding food is crucial for organisms. Whereas specialized animals select a small number of potentially available food sources, generalists use a broader range. Specialist (oligolectic) bees forage on a small range of flowering plants for pollen and use primarily olfactory and visual cues to locate their host flowers. So far,...

With less than a million neurons, the western honeybee Apis mellifera is capable of complex olfactory behaviors and provides an ideal model for investigating the neurophysiology of the olfactory circuit and the basis of olfactory perception and learning. Here, we review the most fundamental aspects of honeybee's olfaction: first, we discuss which o...

In social species, decision-making is both influenced by, and in turn influences, the social context. This reciprocal feedback introduces coupling across scales, from the neural basis of sensing, to individual and collective decision-making. Here, we adopt an integrative approach investigating decision-making in dynamical social contexts. When choo...

The ability to move towards or away from a light source, namely phototaxis, is essential for a number of species to find the right environmental niche and may have driven the appearance of simple visual systems. In this study we ask if the later evolution of more complex visual systems was accompanied by a sophistication of phototactic behaviour. T...

The general architecture of the olfactory system is highly conserved from insects to humans, but neuroanatomical and physiological differences can be observed across species. The American cockroach, inhabiting dark shelters with a rather stable olfactory landscape, is equipped with long antennae used for sampling the surrounding air-space for orien...

Finding the right lure for trapping pest insects is difficult. The typical smell of rain and humid soil, geosmin, now turns out to be a strong attractant for the yellow fever mosquito Aedes aegypti.

Synopsis Insects have highly developed olfactory systems: in many species the olfactory input is the most important sensory information about the environment. Furthermore, odorants are used to communicate within a species (pheromones) and between. In this chapter, the anatomy and the physiology of adult insect olfactory systems is reviewed in a sys...

The general architecture of the olfactory system is highly conserved from insects to humans, but neuroanatomical and physiological differences can be observed across species. The American cockroach, inhabiting dark shelters with a rather stable olfactory landscape, is equipped with long antennae used for sampling the surrounding air-space for orien...

The odorant receptor neurons on the fruit fly antenna are highly sensitive to a broad range of chemicals. A compound signal of receptor activity on the antenna can be read out in real time with functional neuroimaging, and individual receptor responses to hundreds of odorants are available in a database. Utilizing the fruit fly antenna as chemosens...

Honeybees have remarkable learning abilities given their small brains, and have thus been established as a powerful model organism for the study of learning and memory. Most of our current knowledge is based on appetitive paradigms, in which a previously neutral stimulus (e.g., a visual, olfactory, or tactile stimulus) is paired with a reward. Here...

On the basis of long-term (2001–2017) and extensive data (> 1700 breeding attempts), we assess factors influencing breeding parameters in Montagu’s Harrier (Circus pygargus), a medium-sized ground-nesting semi-colonial raptor breeding in cereal fields, in a study area in its core distribution range (Extremadura, Spain). We evaluated annual and long...

The ensemble of odorant receptors on the antenna of the fruit fly Drosophila melanogaster acts as an encoder for chemical molecules. Chemically similar odorants elicit activity in similar subsets of the receptors, spanning a so-called chemotopic feature space that enables chemical similarity search. A compound signal of receptor activity can be rea...

[This corrects the article on p. 128 in vol. 12, PMID: 29867361.].

Animals can form associations between temporally separated stimuli. To do so, the nervous system has to retain a neural representation of the first stimulus until the second stimulus appears. The neural substrate of such sensory stimulus memories is unknown. Here, we search for a sensory odor memory in the insect olfactory system and characterize o...

Related to Figure 4: Post-odor response patterns of ORN axons and PN dendrites differ from odor response patterns. Corresponding graphs as in Figures 3A,B, for cross correlations between stimuli of increasing length (abscissa, from top to bottom), with a stimulus of 10 s length (ordinate, in each graph).

Related to Figure 6: Odor and post-odor responses evolve differently in different brain areas. Corresponding graphs as in Figure 6 for cross correlations between responses to repeated presentation of the same odorant, in PN somata, KC dendrites and KC somata [columns (A–C), respectively]. See methods for odorant abbreviations.

The olfactory stimulator produced odorant pulses, with steep odorant on- and off-sets. Traces show photoionization detector signals (PID, Model 200a, Aurora Scientific Inc.) during stimulation with the tracer substance ethyl acetate (undiluted, ionization potential 10.01 eV) for different pulse lengths (0.2, 0.4, 1, 3, 6 s in channel 1, and 10 s in...

In a recent paper, Joseph and colleagues (Joseph et al., 2017) have characterized an IR60b receptor-expressing neuron in Drosophila. They showed that it responds to sucrose and serves to limit sucrose consumption, and proposed that it may thereby act to prevent overfeeding. Here, we propose an alternative hypothesis for the functional role of sucro...

Animals can follow olfactory traces to find food, detect a sexual mate, or avoid predators. A new study reveals that pheromone-specific projection neurons in the cockroach have a spatially tuned receptive field, and allow encoding spatial information of an odorant.

In a recent paper, Joseph and colleagues (Joseph et al., 2017) have characterized the selective sucrose receptor IR60b in Drosophila , and proposed that it serves to limit sucrose consumption, and thus to prevent overfeeding. Here, we propose an alternative hypothesis for this sucrose receptor. Adult fruit flies feed by excreting saliva onto the fo...

In a recent paper, Joseph and colleagues (Joseph et al., 2017) have characterized the selective sucrose receptor IR60b in Drosophila , and proposed that it serves to limit sucrose consumption, and thus to prevent overfeeding. Here, we propose an alternative hypothesis for this sucrose receptor. Adult fruit flies feed by excreting saliva onto the fo...

Neural activity can be mapped across individuals using brain atlases, but when spatial relationships are not equal, these techniques collapse. We map activity across individuals using functional registration, based on physiological responses to predetermined reference stimuli. Data from several individuals are integrated into a common multidimensio...

Due to the highly efficient olfactory code, olfactory sensory systems are able to reliably encode enormous numbers of olfactory stimuli. The olfactory code consists of combinatorial activation patterns across sensory neurons, thus its capacity exceeds the number of involved classes of sensory neurons by a manifold. Activation patterns are not stati...

The insect antennae receive olfactory information from the environment. In some insects, it has been shown that antennal responsiveness is dynamically regulated by circadian clocks. However, it is unknown how general this phenomenon is and what functions it serves. Circadian regulation in honeybee workers is particularly interesting in this regard...

Dopaminergic neurons (DANs) signal punishment and reward during associative learning. In mammals, DANs show associative plasticity that correlates with the discrepancy between predicted and actual reinforcement (prediction error) during classical conditioning. Also in insects, such as Drosophila, DANs show associative plasticity that is, however, l...

Several studies have attempted to test the vibrational hypothesis of odorant receptor activation in behavioral and physiological studies using deuterated compounds as odorants. The results have been mixed. Here, we attempted to test how deuterated compounds activate odorant receptors using calcium imaging of the fruit fly antennal lobe. We found sp...

The honey bee is an excellent visual learner, but we know little about how and why it performs so well, or how visual information is learned by the bee brain. Here we examined the different roles of two key integrative regions of the brain in visual learning: the mushroom bodies and the central complex. We tested bees' learning performance in a new...

The honeybee has been established as an important model organism in studies on visual learning. So far the emphasis has been on appetitive conditioning, simulating floral discrimination, and homing behavior, where bees perform exceptionally well in visual discrimination tasks. However, bees in the wild also face dangers, and recent findings suggest...

Male moths possess a highly specialized olfactory system comprised of two segregated sub-arrangements dedicated to processing information about plant odors and pheromones, respectively. Communication between these two sub-systems has been described at the peripheral level, but relatively little is known about putative interactions at subsequent syn...

DNA methyltransferases (Dnmts) - epigenetic writers catalyzing the transfer of methyl-groups to cytosine (DNA methylation) – regulate different aspects of memory formation in many animal species. In honeybees, Dnmt activity is required to adjust the specificity of olfactory reward memories and bees’ relearning capability. The physiological relevanc...

Animals encounter fine-scale temporal patterns of odorant mixtures that contain information about the distance and number of odorant sources. To study the role of such temporal cues for odorant detection and source localization, one needs odorant delivery devices that are capable of mimicking the temporal stimulus statistics of natural odor plumes....

The honeybee Apis mellifera is an established model for the study of visual orientation. Yet, research on this topic has focused on behavioral aspects and has neglected the investigation of the underlying neural architectures in the bee brain. In other insects, the anterior optic tubercle (AOTU), the lateral (LX) and the central complex (CX) are im...

Insects primarily rely on olfaction when locating resources such as food or mating partners. Tracking down the source of an odor poses a particular challenge: air turbulences break odor plumes into intermittent filaments which intermingle with filaments of background odors. This creates temporally and spatially complex patterns of different odor co...

The activity of the epigenetic writers DNA methyltransferases (Dnmts) after olfactory reward conditioning is important for both stimulus-specific long-term memory (LTM) formation and extinction. It, however, remains unknown which components of memory formation Dnmts regulate (e.g. associative vs. non-associative) and in what context (e.g. varying t...

The Drosophila larva has a simple peripheral nervous system with a comparably small number of sensory neurons located externally at the head or internally along the pharynx to assess its chemical environment. It is assumed that larval taste coding occurs mainly via external organs (the dorsal, terminal, and ventral organ). However, the contribution...

N,N-Diethyl-meta-toluamide (DEET) is the most widely used insect repellent, but it requires repeated application at high, potentially harmful, concentrations, which is prohibitively impractical and costly in the countries suffering most from insect vector-borne diseases1; understanding DEET’s mode of action might help identify improved alternatives...

DNA methyltransferases (Dnmts) - epigenetic writers catalyzing the transfer of methyl-groups to cytosine - regulate stimulus-specific olfactory long-term memory (LTM) formation and extinction in honeybees. The physiological relevance of their function in neural networks, however, remains unknown. Here, we investigated how Dnmts impact neuroplastici...

Odors elicit complex patterns of activated olfactory sensory neurons. Knowing the complete olfactome, i.e. the responses in all sensory neurons for all relevant odorants, is desirable to understand olfactory coding. The DoOR project combines all available Drosophila odorant response data into a single consensus response matrix. Since its first rele...

Scientific Reports 5 : Article number: 16223 10.1038/srep16223 ; published online: 04 November 2015 ; updated: 25 February 2016 . This Article contains an error in the order of the Figures.

The medfly Ceratitis capitata is one of the most important pests for horticulture worldwide. The knowledge about anatomy and function of the medfly olfactory system is still limited. The first brain structure to process olfactory information in insects is the antennal lobe (AL), which is composed of its functional and morphological units, the olfac...

DNA methylation and demethylation are epigenetic mechanisms involved in memory formation. In honey bees DNA methyltransferase (Dnmt) function is necessary for long-term memory to be stimulus specific (i.e. to reduce generalization). So far, however, it remains elusive which genes are targeted and what the time-course of DNA methylation is during me...

Odors elicit complex patterns of activated olfactory sensory neurons. Knowing the complete olfactome, i.e. responses in all sensory neurons for all odorants, is desirable to understand olfactory coding. The DoOR project combines all available Drosophila odorant response data into a single consensus response matrix. Since its first release many stud...

This chapter describes the challenges faced by the olfactory system of terrestrial insects and how insects cope with such challenges. It discusses the basic circuitry of odor coding in the insect brain. For many insects, olfaction is the main sensory system. The chapter provides few examples of how odors are used by different insects, taking into a...

Gravid mosquitoes use chemosensory (olfactory, gustatory, or both) cues to select oviposition sites suitable for their offspring. In nature, these cues originate from plant infusions, microbes, mosquito immature stages, and predators. While attractants and stimulants are cues that could show the availability of food (plant infusions and microbes) a...

The question of how animals process stimulus mixtures remains controversial as opposing views propose that mixtures are processed analytically, as the sum of their elements, or holistically, as unique entities different from their elements. Overshadowing is a widespread phenomenon that can help decide between these alternatives. In overshadowing, a...

Honey bees are important model systems for the investigation of learning and memory and for a better understanding of the neuronal basics of brain function. Honey bees also possess a rich repertoire of tones and sounds, from queen piping and quacking to worker hissing and buzzing. In this study, we tested whether the worker bees' sounds can be used...

Vision and olfaction are two key sensory modalities used by insect herbivores to locate and exploit host plants. Here, we provide examples of synergisms documented at the level of behavior and neurophysiology within (olfaction) and across (olfaction and vision) sensory modalities for various species of insect pests. For fruit flies (Diptera: Tephri...

Significance How fast can animals smell? Whereas we know how fast our eyes are (in the cinema, images at 24 Hz fuse for humans, whereas our retina can resolve flickers at more than 100 Hz), olfactory perception is believed to be slow. After all, we take a sniff and later another one. Odor plumes in the air, however, can fluctuate at a millisecond t...

Background: Insect behavior is often monitored by human observers and measured in the form of binary responses. This procedure is time costly and does not allow a fine graded measurement of behavioral performance in individual animals. To overcome this limitation, we have developed a computer vision system which allows the automated tracking of bo...

Extracting motion trajectories of insects is an important prerequisite in many behavioral studies. Despite great efforts to design efficient automatic tracking algorithms, tracking errors are unavoidable. In this paper, we propose general principles that help to minimize the human effort required for accurate multi-target tracking in the form of ap...

Methyl N,N-dimethyl anthranilate (MDA), ethyl anthranilate (EA) and butyl anthranilate (BA) were previously shown to repel Aedes aegypti mosquitoes from landing on human skin. However, the effect of these compounds on the orientation of flying mosquitoes in a choice situation and their effect on mosquito oviposition are not yet known. Here, we used...

Background p-cresol (4-methylphenol) and its isomer m-cresol (3-methylphenol) have been shown to activate the same sensilla in Aedes aegypti (Linnaeus) mosquitoes. Whereas p-cresol has been suggested to play a role in oviposition site choice, the behavioral significance of m-cresol is unknown. Methods Here, we assayed the oviposition behavior of A...

Odours can be used to detect cancer Diagnosing diseases by the smell and taste of bodily samples goes back to ancient history. While the smell of some infections or metabolic diseases has been used as a diagnostic tool for a long time, it has only recently been observed that cancer is also detectable by its specific scent. The first reports about...

Motivated by the analysis of glomerular time series extracted from calcium-imaging data, asymptotic theory for piecewise polynomial and spline regression with partially free knots and residuals exhibiting three types of dependence structures (long memory, short memory and anti-persistence) is considered. Unified formulas based on fractional calculu...

Much progress has been made recently in understanding how olfactory coding works in insect brains. Here, I propose a wiring diagram for the major steps from the first processing network (the antennal lobe) to behavioral readout. I argue that the sequence of lateral inhibition in the antennal lobe, non-linear synapses, threshold-regulating gated spr...

Insects have a remarkable ability to identify and track odor sources in multi-odor backgrounds. Recent beha-vioral experiments show that this ability relies on detecting millisecond stimulus asynchronies between odors that originate from different sources [1]. Honeybees are able to distinguish mixtures where both odors arrive at the same time (sync...

Intracellular signaling in insect olfactory receptor neurons remains unclear, with both metabotropic and ionotropic components being discussed. Here, we investigated the role of heterotrimeric Go and Gi proteins using a combined behavioral, in vivo and in vitro approach. Specifically, we show that inhibiting Go in sensory neurons by pertussis toxin...

Cancer cells and non-cancer cells differ in their metabolism and they emit distinct volatile compound profiles, allowing to recognise cancer cells by their scent. Insect odorant receptors are excellent chemosensors with high sensitivity and a broad receptive range unmatched by current gas sensors. We thus investigated the potential of utilising the...

Intracellular signaling in insect olfactory receptor neurons remains unclear, with both metabotropic and ionotropic components being discussed. Here, we investigated the role of heterotrimeric Go and Gi proteins using a combined behavioral, in vivo and in vitro approach. Specifically, we show that inhibiting Go in sensory neurons by pertussis toxin...

Calcium imaging in insects reveals the neural response to odours, both at the receptor level on the antenna and in the antennal lobe, the first stage of olfactory information processing in the brain. Changes of intracellular calcium concentration in response to odour presentations can be observed by employing calcium-sensitive, fluorescent dyes. Th...

Understanding the functions of sleep and dreaming requires that we understand how the brain processes sensory information. Do we replay and consolidate memories during sleep? When insects sleep, do they process sensory information in a manner similar to their processing of sensory information while awake? European honey bees (Apis mellifera), when...