Martin Giurfa

The study of gustatory pathways from the periphery to the brain offers valuable insights into the neural mechanisms underlying taste processing and foraging choices, particularly in ecologically and economically relevant species such as the honey bee, Apis mellifera . While the neural substrates of other sensory modalities in bees, notably olfaction and vision, have been thoroughly characterized, the organization principles of gustatory pathways in the primary gustatory center (the subesophageal zone, SEZ) and brain of this species remain largely unexplored. Using anterograde mass staining with dextran‐coupled fluorescent tracers applied into the main gustatory appendages (antennae, mouthparts, and foreleg tarsi), we identified the projection areas of their sensory afferents within the SEZ. Our results show that sensory circuits are confined to specific, distinct regions of the SEZ, suggesting the presence of somatotopic “maps” corresponding to the different appendages. Overlaps between projections, reflecting potential information exchange between appendicular domains in the SEZ, were most evident among inputs originating from similar appendages (e.g., between mouthparts—proboscis and mandibles) and were limited between domains of different appendages (e.g., antennae and mouthparts). We also confirm the subesophageal‐calycal tract (SCT) as the main output of the SEZ. Combined retrograde staining of the SCT and anterograde staining of taste appendages revealed that SCT dendrites overlap specifically with sensory input from the maxillae in the SEZ. The functional significance of these findings is discussed in the context of gustatory information processing during bee feeding behavior, and the results are considered within a comparative framework across insect taxa.

The idea that invertebrates may exhibit basic forms of emotion, and possibly sentience, is gaining traction as evidence of their advanced cognitive abilities continues to mount. While high-level cognition does not imply emotional states, invertebrates offer a unique window into whether such states can arise in small-brained animals. With their relatively simple yet highly structured nervous systems, they serve as tractable models for dissecting the mechanisms underlying emotional expression. To probe these processes, researchers have developed behavioural paradigms exposing different species to contexts likely to elicit emotional responses. From a phylogenetic perspective, studying emotional expression in invertebrates can reveal whether basic emotional systems are conserved across species. This review synthesizes current knowledge of non-verbal emotional expression in social insects, focusing on mechanisms and functional roles. We apply a multi-component approach to examine key building blocks shared across emotions and taxa, offering insights into their evolutionary origins. We also identify critical gaps in knowledge and propose directions for future research. By examining the proximate and ultimate causes of emotion, this framework enhances our understanding of the biological basis and evolutionary significance of emotions, promoting interdisciplinary research that bridges neuroscience, ethology and evolutionary biology. This article is part of the theme issue ‘Mechanisms, development, phylogeny and functions of emotional expressions’.

Neuropeptide activity in honey bees varies with age, behavioral role, and season. The short neuropeptide F (sNPF) modulates foraging-related behaviors in summer foragers, including food intake, sucrose sensitivity, and sensory processing, but its role in other castes remains unknown. Winter bees and nurses are two phenotypes, which are considered similar due to their substantial internal energetic reserves. Yet, their appetitive profiles have never been characterized. Here, we combined electrophysiological, behavioral and neuropeptide supplementation approaches to compare appetitive behaviors across bees of different behavioral castes and ages, with or without sNPF supplementation. sNPF treatment enhanced sucrose responsiveness in winter bees and olfactory responses in nurses. Our results reveal distinct appetitive profiles, challenge the assumption that nurses and winter bees behave similarly, and highlight that appetitive motivation is multidimensional. Specifically, they show that phenotype and season can decouple peripheral sensitivity, central responsiveness, learning performance, and food consumption.

A recent study provided evidence for emotional contagion in bumble bees, thus raising questions about the evolutionary origins of emotions and their social components. Although evidence for affective contagion is compelling, the mechanisms and cues allowing this emotional transfer remain unclear and require further exploration. (PsycInfo Database Record (c) 2026 APA, all rights reserved).

The question of whether awareness is required for trace but not for delay conditioning has recently been explored in the honeybee, a species renowned for its cognitive abilities. Distractors impair trace but not delay absolute olfactory conditioning, suggesting that bees, like humans, rely on awareness of the conditioned stimulus–unconditioned stimulus contingency during trace learning. Here, we extend this approach to reversal learning, which requires learning an initial discrimination (A+ B−) and subsequently learning the reversed contingencies (A−B+). Bees mastered olfactory reversal learning under both delay and trace protocols but acquisition was slower and less robust under trace than under delay conditioning. Introducing a visual distractor during the reversal phase impaired performance in distinct ways. Delay-conditioned bees increased responsiveness, adopting an A+B+ response profile, whereas trace-conditioned bees decreased responsiveness, adopting an A⁻B⁻ profile. To our knowledge, this is the first study in any animal species investigating reversal learning under a trace-conditioning regime, and the first assessing distractor effects in this paradigm. The contrasting outcomes indicate that the distractor disrupted attentional reallocation in both protocols, but additionally interfered with awareness in trace learning. These findings provide evidence that bees engage awareness-like processes during trace reversal learning, highlighting cognitive processing in an insect.

Understanding the mechanisms underlying animal cognition requires experimental designs and analyses that respect the biological and perceptual constraints of the species being studied. We address an ongoing debate regarding the role of visual spatial frequency in numerical cognition studies, using honeybees (Apis mellifera) as a model system. Prior analyses that excluded the low spatial frequencies known to be fundamental to how these insects use their spatial vision may have introduced spurious correlations between visual features and numerical cues. By recalculating stimulus properties while incorporating the biologically relevant spectrum of spatial frequencies perceivable by a bee, our results suggest that numerical cognition in honeybees is not driven by spatial frequency but instead reflects true numerosity processing. This work highlights the necessity of aligning experimental design and analysis with the sensory and perceptual abilities of the studied species to ensure biologically meaningful conclusions. To support this goal, we provide a general framework for designing experiments that respect the psychophysical constraints of animal models in numerical cognition studies.

Humans and animals share basic abilities to represent numerosity, called number sense, which underpins human abstract numerical skills. A key feature is Spatial-Numerical Association (SNA): the association of small numbers with the left and large ones with the right space. Initially observed in human adults using symbolic numbers, SNA has been found in newborns and animals using non-symbolic numerosity. This discovery initiated a debate on the SNA's origins: Is the use of space to represent numbers a learning outcome or an inherited predisposition? This review presents an up-to-date, comprehensive overview on systematic developments in SNA. Specifically, it 1) organizes the present literature by tracing back the emergence of SNA in humans, primates, birds and invertebrates; 2) outlines SNA modulation over the lifespan; 3) critically compares the most influential models regarding the origin and modulation of SNA; 4) expands the focus by providing evidence on SNA in arithmetic; 5) suggests future research directions. From this comprehensive overview, it emerges that a biological predisposition to associate numerosity with space is inherent in nervous systems endowed with a number sense, irrespective of their neural complexity. Strength and orientation of SNA are then modulated by ontogenetic aspects and adapted to solve contingent problems. Importantly, SNA plays a crucial role in mathematical cognition. This holistic understanding of how SNA emerges, evolves and adapts provides a new perspective from which to refine both the conceptual and methodological definitions of SNA, with important implications for the development of efficient mathematical brains.

Despite having a miniature brain—smaller than one cubic millimeter and comprising roughly one million neurons—honey bees display a rich behavioral repertoire in which learning and memory play a central role. This raises the question of whether their adaptive behavior extends beyond simple forms of learning, and whether the neural mechanisms underlying complex cognition can be elucidated in this insect model. Elemental olfactory conditioning, where bees learn to associate an odorant with a sucrose reward, has provided an unparalleled framework to dissect the neural circuits underlying conditioned (odor) and unconditioned (sucrose) stimulus processing. This work revealed how these pathways converge in the brain—particularly within the antennal lobes, lateral horn, and mushroom bodies—and how learning reshapes neural coding, notably at the level of the antennal lobe. Beyond elemental tasks, bees master non-elemental discriminations such as negative patterning and biconditional learning, which require configural processing. Neural interference studies identify the mushroom bodies as essential for these higher-order functions. Even more complex capacities have been demonstrated: bees categorize visual stimuli, learn abstract rules (sameness, difference, above/below), transfer learning across sensory modalities, and display numerical competence, including rudimentary arithmetic and an understanding of zero. Together, these findings reveal a degree of cognitive sophistication once thought unique to vertebrates and establish the honey bee as a powerful system for investigating both basic and advanced cognitive processes, as well as their neural foundations, within a miniature brain.