Biology subjects

Zordan, M. A.

Publications and source records attributed to Zordan, M. A..

6 recordsLinked to original sources

bioRxiv2026

Repellent olfactory cues influence the optomotor response modulation in Drosophila melanogaster

Animals need to precisely perceive and integrate the environmental cues to orient and select the appropriate motor responses required for navigating. This is the case, for instance, of the optokinetic reflex (OKR) and the optomotor response (OMR) in Drosophila melanogaster, where optic flow stimulation modulates the head or the body and legs motor activity respectively. Despite large bodies of literature on both the OKR and the OMR, there is still a limited understanding, in flies, of the impact on these responses of concomitant, and potentially conflicting, sensory inputs. To investigate this aspect, we used fruit flies walking on a sphere, presented with optic flow stimulation leading to the OMR together with the simultaneous exposure to olfactory stimulation, either using established repellent or masking compounds. We analysed the effect of different substances, and of their concentration, on the dynamics of the flies response to moving gratings, evaluating the fly walking path as well as average speed and duration. This analysis revealed several alterations between the compounds tested, in agreement with reported data on the simpler OKR. In conclusion, we show that concomitant exposure to repellents and maskers may consistently affect fundamental processes (the OKR and OMR) available to insects for informing themselves while navigating through the environment.

animal behavior and cognition↗

bioRxiv2025

A Syntaxin1A protein mutation drives sleep reduction in Drosophila

Syntaxin1A is a key component in the regulation of the vesicle fusion nanomachine and, together with VAMP/synaptobrevin and SNAP-25, forms the core of the SNARE complex, that is the molecular nanomachine regulating neurotransmitter release. Syntaxin1A is localized on the cytosolic face of the presynaptic membrane and with Munc-18-1 is thought to be the starting point for the SNARE complex assembly.1 In flies, aspartic-to-arginine amino acid substitution at position 253 of the protein sequence reduces synaptic release by affecting the assembly of multiple SNARE complexes into a super-complex without interfering with the single complex formation per se.2 In this study, we analyzed sleep behavior in flies expressing this mutated isoform of Syntaxin1A panneuronally. According to the synaptic homeostasis hypothesis,3 the overall decrease of synaptic activity during the previous period of wakefulness should reduce the need for sleep.4 We observed a reduction in the total amount of sleep in flies expressing the mutated isoform compared to controls. Moreover, the sleep pattern of the Syntaxina1A mutant flies was more fragmented compared to controls. Video-tracking analysis of free walking flies in an open-field arena showed that these changes were not caused by higher locomotor activity during the daytime relative to controls. Our results suggest that the widespread effect of Syntaxin1A mutation on synapses may lead to a dampening of the information load among neurons and, consequently, impact the regulation of sleep at the cellular level. HighlightsO_LIThe neurotransmitter release machinery modulates sleep in Drosophila C_LIO_LIA Syntaxin1A protein mutation causes fragmented night sleep C_LIO_LIMotor activity is not affected by the Syntaxin1A mutation C_LIO_LISyntaxin1A could regulate the homeostasis of vesicle fusion and sleep C_LI In briefFrighetto et al., investigated the role of a single amino acid substitution in the Syntaxin1A protein in sleep and locomotor behavior. Following the pan-neuronal expression of this mutated Syntaxin1A, they found a specific reduction of sleep with locomotion remaining largely unaffected.

neuroscience↗

bioRxiv2024

Optokinetic response in D. Melanogaster reveals the nature of common repellent odorants.

Animals ability to orient and navigate relies on selecting an appropriate motor response based on the perception and integration of the environmental information. This is the case, for instance, of the optokinetic response (OKR) in Drosophila melanogaster, where optic flow visual stimulation modulates the walking or flying patterns. Despite a large body of literature on the OKR, theres still a limited understanding of the impact on OKR of concomitant, potentially conflicting, inputs. To evaluate the impact of this multimodal integration, we combined in D. melanogaster, while flying in a tethered condition, the optic flow stimulation leading to OKR with the simultaneous presentation of olfactory cues, based on repellent or masking compounds typically used against noxious insect species. First, this approach al lowed us to directly quantify the effect of several substances and their concentration, on the dynamics of the flies OKR in response to moving gratings by evaluating the number of saccades and the velocity of its slow phase. Subsequently, this analysis was capable of easily revealing the actual effect, i.e. masking vs repellent, of the compound tested. In conclusion, we show that D. melanogaster, a cost-affordable species, represents a viable option for studying the effects of several compounds on the navigational abilities of insects.

animal behavior and cognition↗

bioRxiv2020

Hierarchical Spatial Search Strategies in Drosophila

Humans rely on multiple systems of sensory information to make decisions. However, strategies that shorten decision-making time by taking into account fewer but more essential elements of information are preferred to strategies involving complex analyses. These "shortcuts to decision" are also termed "heuristics". The identification of heuristic principles in species phylogenetically distant to humans would shed light on the evolutionary origin of speed-accuracy trade-offs and offer the possibility to investigate the brain representations of such trade-offs, urgency, and uncertainty. During experiments on spatial learning, we acknowledged that the search strategies of the invertebrate Drosophila melanogaster, the common fruit fly, resembled a spatial heuristic. Here we show that the fruit fly applies a heuristic termed the "Nearest Neighbour Rule" to avoid bitter taste (a negative stimulation). That is, the fly visits the salient location closest to its current position to hopefully stop the negative stimulation. Only if this strategy proves unsuccessful, the animal uses other learned associations to avoid bitter taste. The acknowledgement of a heuristic in D. melanogaster supports the view that invertebrates can leverage on economic principles when making choices and that the existence of heuristics in evolution dates to at least 600 million years ago.

neuroscience↗

bioRxiv2019

Searching for relief: Drosophila melanogaster navigation in a virtual bitter maze

Animals use pain-relief learning to discern which actions can diminish or abolish noxious stimuli. If relief from pain is provided in a specific location, place learning is the mechanism used to pinpoint that location in space. Little is known about how physiological and non-directly damaging stimuli can alter visual-based searching behaviour in animals. Here we show how the optogenetically-induced activation of bitter-sensing neurons urges Drosophila melanogaster to seek relief from bitter taste stimulation and that this distressful, but ecologically relevant stimulus, innately wired to the threat of intoxication, is sufficient to elicit pain-relief-like behavioural responses. Specifically, freely walking flies inside an open circular arena are trained to seek relief from the unpleasant stimulation by searching for a safe area alternatively positioned in the proximity of a pair of identical, diametrically opposed, visual markers. Moreover, and perhaps more importantly, under this paradigm flies develop visual place learning manifested by their seeking relief in the zone associated with bitter relief during the last trial of training, even when exposed to constant bitter stimulation with no relief provided. An important implication is that this form of learning does not lead to operant conditioning generalization. We further propose that kinematic indexes, such as the spatially-specific reduction of locomotor velocity, may provide immediate evidence of relief-based place learning and spatial memory.

animal behavior and cognition↗

bioRxiv2018

Mechanisms of selection for the control of action in Drosophila melanogaster

In the last few years several studies have investigated the neural mechanisms underlying spatial orientation in Drosophila melanogaster. Convergent results suggest that this mechanism is associated with specific neural circuits located within the Central Complex (CC). Furthermore such circuits appear to be associated with visual attention, specifically with selective attention processes implicated in the control of action. Our aim was to understand how wild-type flies react to the abrupt appearance of a visual distractor during an ongoing locomotor action. Thus, we adapted the well-known Buridan paradigm, used to study walking behaviour in flies, so we could specifically address the mechanisms involved in action selection. We found that flies tended to react in one of two ways when confronted with a visual distractor during ongoing locomotion. Flies either: (i) committed to a new path situated midway between the original target and the distractor, consistent with a novelty effect; or (ii) remained on the original trajectory with a slight deviation in direction of the distractor. We believe that these results provide the first indication of how flies react, from the motor point of view, in a bi-stable context requiring the presence of selection-for-action mechanisms. Some considerations on the neural circuits underlying such behavioural responses are advanced.

animal behavior and cognition↗