Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2024.10.22.619725

Limitations of grouping subjects based on biological sex (males versus females) and a new approach: insights from intra-nucleus accumbens core dopamine-induced psychostimulant activity.

Job, M. O.
View original source ↗Export metadata ↓

Abstract

BackgroundIn the field of substance use disorder research, sex-as-a-biological-variable (SABV) is employed to determine the mechanisms governing sex differences. Based on our recently developed MISSING (Mapping Intrinsic Sex Similarities as an Integral quality of Normalized Groups) model, we hypothesized that grouping subjects by biological sex does not represent the most effective way to group behavioral data objectively. To test our hypothesis, we conducted experiments to compare the psychostimulant effect of intra-nucleus accumbens (NAc) dopamine on groups based on 1) biological sex (current model) and 2) behavioral clustering (MISSING model) for effectiveness in identifying groups of subjects that a) are distinct with regards to behavioral variables, and b) confirm NAc dopamine neurochemical expression/activity topography (NEAT). MethodsFor the current model, we separated subjects (n = 37 Sprague Dawley rats, male n = 20, female n = 17) by biological sex prior to all assessments. For the MISSING model, we conducted normal mixtures clustering of baseline activity, dopamine activity (as distance traveled in cm over 60 min) and dopamine activity normalized-to-baseline activity (NBA) of all subjects to identify behavioral clusters. ResultsSeparating groups by biological sex revealed groups (males and females) that were not clearly distinct with regards to behavioral variables and do not confirm NAc dopamine NEAT. Separating groups using the MISSING model revealed groups (behavioral clusters) that were clearly distinct with regards to behavior and confirm NAc dopamine NEAT. ConclusionsOur results reveal the limitations of grouping subjects based on biological sex. We discuss a new approach.

Explore related subjects

neurosciencePreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Job, M. O.. 2024-10-22. Limitations of grouping subjects based on biological sex (males versus females) and a new approach: insights from intra-nucleus accumbens core dopamine-induced psychostimulant activity.. https://doi.org/10.1101/2024.10.22.619725

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

A highly reproducible, safe cranial window surgery for targeted in vivo manipulations in the adult zebrafish telencephalon

Experimental surgery is one of the most fundamental fields of biomedical research, recreating clinical conditions on living organisms similar to clinical patients, to facilitate the design of novel therapies. For modeling neurological and psychiatric disorders, the majority of operative techniques mandatorily include craniotomy for consecutive interactions with the open brain. The most wide-spread methodology involves stereotactic surgery in rodents, implementing a specific head holder, attached to the coordinate table, providing the precise animal head positioning according to the brain structures topology. Despite the high efficiency, such systems require complex instrumental skills and long procedure duration per animal even for simple implantation protocols. Hence, novel alternative model species could be a valuable supplementary tool for such manipulations. Therefore, the zebrafish (Danio rerio) fits perfectly, due to its low cost, easy husbandry, rapid development, optic transparency, and high genetic and physiological similarity to rodents and humans. Furthermore, the everted zebrafish telencephalon provides excellent accessibility to critical mammalian-like structures involved in emotion processing and cognition. However, conventional avian- or rodent-inspired craniotomies in adult zebrafish often trigger inadvertent disruption of the brain vessels network, resulting in high operative mortality. A novel, geometry-driven, non-lethal cranial window protocol preserving neurovascular integrity and ensuring 90-100% post-operative survival is presented to overcome above mentioned limitations. This rapid, simple, and high reproducible technique opens new avenues for precise region-specific in vivo neurosurgery, high-throughput psychopharmacological screening, and neurostimulation in a powerful non-mammalian model species

neuroscience↗
bioRxiv2026

Functional Connectivity Differences Underly Variable Centralized Symptom Relief After Hysterectomy

Approximately 1 in 4 women with chronic pelvic pain (CPP) report persistent pelvic pain after hysterectomy. Centralized symptoms-fatigue, multisite pain, and sleep disturbance, quantified using the Fibromyalgia Survey Score (FSS)-often co-occur with this risk, but the trajectory of centralized symptom burden after surgery, independent of pelvic pain outcome, is not well understood. Whether presurgical differences in central nervous system pain processing distinguish women whose centralized symptoms improve (improvers) from those whose do not (non-improvers) has not been tested. In this observational study, we assessed whether individuals who do and do not report improvement in FSS scores six months post-operatively differ in their baseline/pre-operative phenotypes and brain function. Sensory sensitivity scores were significantly higher in non-improvers than in improvers at baseline. We identified no significant, presurgical differences in age, average pelvic pain intensity, widespread pain, or pain interference between improvers and non-improvers. Functional connectivity was examined at rest and during the application of a distal, sustained pressure pain. We identified no significant group differences at rest. During sustained pressure pain, non-improvers showed greater connectivity than improvers between primary somatosensory cortex and posterior thalamic seeds with frontal, motor, cerebellar and limbic regions, but lower connectivity between the periaqueductal gray and subgenual cingulate cortex. Non-improvers also showed a greater pain-evoked increase in connectivity between the pelvic and leg representations of the primary sensory cortex and other sensorimotor regions in the pain-versus-rest contrast. Overall, non-improvers showed increased functional connectivity between regions associated with the multisensory integration of ascending pain, and decreased connectivity between regions associated with descending pain modulation. In exploratory analyses, some of these connections were additionally associated with symptom burden: sensory sensitivity, number of painful regions, and pain interference. This work may inform mechanisms of persistent symptom burden and guide surgical decision-making in patients with high central sensitization.

neuroscience↗
bioRxiv2026

Heteroskedasticity of neuronal population responses

Typical changes in a neuronal circuit's operating regime - such as shifts in sensorimotor conditions or in brain state - reshuffle firing rates across its neurons. One well-established key organising principle is rate preservation: firing rates correlate strongly across conditions. Here, we demonstrate that the joint distribution of firing log-rates across pairs of conditions exhibits an additional pervasive and previously unrecognised property: strong heteroskedasticity around the rate-preservation axis, whereby slow-firing neurons (< 1 spike/s) display substantially more variable relative responses across conditions than fast-firing neurons (>10 spikes/s). Using large-scale recordings across multiple brain regions (visual cortex, hippocampus, thalamus, and motor cortex) in mice and primates, we demonstrate that this structure is a generic feature of neuronal population responses. A spike subsampling procedure and explainable variance analysis confirm that this heteroskedasticity reflects true biophysical variance rather than statistical estimation bias resulting from low spike counts. Rate and spiking network models reproduce this phenomenon, revealing its key mechanism: while the standard neuronal transfer function (the F-I curve) is convex, its log-rate counterpart (the logF-I curve) is concave. Consequently, for equivalent input current shifts slow-firing neurons exhibit greater relative sensitivity whereas fast-firing neurons exhibit greater absolute sensitivity. Finally, we show that heteroskedasticity strongly influences downstream readout. Under wiring constraints, neurons with intermediate firing rates provide optimal discrimination performance, whereas under metabolic constraints, large assemblies of slow-firing neurons are most advantageous. These findings identify heteroskedasticity as a fundamental organising principle of neuronal population responses, establishing a mechanistic link between non-linear cellular transfer functions, population-level responses and energy-efficient representations.

neuroscience↗