Pozeilov H¹, Levi M¹, Dayan E¹, Forkosh O² & Shohat-Ophir G ¹

Individual differences, also referred to as personality, are a fundamental characteristic of living organisms and play a crucial role in our understanding of behavior. In humans, the most widely accepted model of personality is based on five continuous dimensions, with each individual scoring differently across these factors. Recent developments in machine vision and learning algorithms have made it possible to detect and analyze a continuous range of inter-individual differences in non-human organisms. To explore this in Drosophila, we employed linear discriminant analysis (LDA) to identify new behavioral dimensions, which we refer to as identity domains. These domains reflect maximal behavioral variation between individuals while maintaining consistency within individuals over time. Using this computational framework, we investigated the complex relationships between social interaction, personality, and motivational states in flies. Our experimental paradigm involved male and female flies subjected to different social and sexual experiences for four days, after which their social group interactions were recorded. The findings offer compelling evidence of distinct inter-individual differences in Drosophila, pointing toward the presence of personality-like traits in flies. We identified four novel identity domains that differentiate between males and females and distinguish between different social and sexual experiences. In addition, we examined how the microbiome's absence affects flies' personality. Our data suggest that the lack of a microbiome leads to a significant shift in the distribution of individual flies across identity space. We developed a single-fly two-choice, operant learning paradigm, in which flies learn to self-stimulate their Neuropeptide F expressing (NPF) neurons (presumably due to its rewarding value), by touching an electrode that induces optogenetic activation of a channel rhodopsin expressed in NPF neurons. We find inter-individual differences in learning kinetics associated with motivational state and NPF levels.

¹ The Mina & Everad Goodman Faculty of Life Sciences, The Multidisciplinary Brain Research Center and the Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Israel

² Department of Cognitive and brain Science, Department of Animal Sciences, Israel

Jean-Richard-dit-Bressel, Philip¹

Individuals differ in their responsivity to the adverse consequences of their actions, with many persisting in highly detrimental behaviour. Despite its relevance to everyday decision-making and clinical conditions, experimental tasks used to study this phenomenon often fail to reveal psychological causes for these inter-individual differences. We addressed this by developing rat, human, and mouse versions of a conditioned punishment task that efficiently disentangles key psychological underpinnings for these differences. Across species, we find avoidance of negative consequences is bimodally distributed across individuals. We show these differences in avoidance are not primarily driven by differences in appetitive or aversive motivation, nor differences in behavioural control. Rather, behavioural differences were primarily due to failures in Action-Punisher learning, indicating an overlooked source of punishment insensitivity. Preliminary data showing how this task is being leveraged for deeper insight into neural mechanisms will also be discussed.

1. School of Psychology, University of New South Wales, Sydney, Australia.

J.D. Jentsch¹

Operant responding for natural or pharmacological reinforcers exhibits substantial individual variation, with a sizeable fraction of that variability being explained by heritable genetic factors. Consistent with our observation that strains from the hybrid mouse diversity panel (HMDP) exhibit extreme differences in operant intravenous cocaine self-administration, we evaluated the acquisition and performance of an action that was reinforced with sucrose solution, using Fixed/variable ratio schedules of reinforcement across 3 long-access sessions in 81 HMDP strains. Across the panel, total lever presses made during the 36 hours of testing ranged from ~0 to almost 7,000 (~195 presses/hr), with a heritability estimate of ~28%. We next studied 8 inbred strains that spanned the range of non-zero operant responding (MRL/MpJ>C57BL/10J>=BALB/cJ>C57BL/6J>DBA/2J>A/J); mice were trained to lever press for a chocolate-flavored BOOST reinforcer. Mice were evaluated using a progressive ratio schedule of reinforcement, in which the response requirements doubled after each schedule completion. Strain differences in responding on the progressive ratio test were observed, with a heritability estimate of ~20%. When different mice from the same strains were evaluated for nucleus accumbens core dopamine release using fast scan cyclic voltammetry in acute brain slices, we found a positive genetic correlation between lever responding in the progressive ratio task and uM dopamine release (r[4]=.831, p=.041). These results suggest that genetic variation present in common inbred strains alters the excitability of dopamine release into the nucleus accumbens and creates substantial differences in motivation to obtain a salient positive reinforcer.

¹Department of Psychology, Binghamton University, Binghamton NY U.S.A.

Funding Support: US Public Health Service Grants P50-DA039841 and T32-AA025606

Hernandez, John S¹., Le, Nelson.², Azanchi, Reza.¹, Glenn, Eve.¹, and Kaun, Karla .R.¹

The escalation of alcohol self-administration is a critical factor in the transition from alcohol use to compulsive drinking, a significant global health concern. While much research has focused on the neural mechanisms driving excessive alcohol intake, there is a pressing need to understand the neural substrates that underlie individual differences in alcohol preference and seeking. This understanding is essential for unraveling why escalation occurs in some individuals but not others, which is key to addressing variability in motivated response. Using Drosophila melanogaster, an ideal model due to its well-characterized neural circuits and genetic tools, we developed a 3-day operant paradigm to assess behaviors related to self-administration of volatilized ethanol. Our findings reveal a simple 2-neuron cholinergic and dopaminergic circuit within the mushroom body that modulates ethanol preference, with implications for how experience shapes this preference over time. We identified dopamine receptors within this circuit that influence ethanol preference, highlighting how individual variation in motivated behavior may emerge from specific neural pathways. Finally, we identified transcriptional changes that are epigenetically regulated within our genetically homogenous population. These insights are critical for understanding the mechanisms that drive alcohol preference, which can predict the likelihood of developing dependence.

1 - Brown University, RI. Department of Neuroscience

2 - Post-baccalaureate Research Education Program, Brown University, Providence, RI

Funding support was provided by the NIAAA R01AA024434 (supporting N.J.M, R.A., K.R.K.), NIAAA F32AA29595 (supporting J.S.H.) and NIGMS R25GM125500 (supporting N.L.).