Adolescence represents an extended period of neuroplasticity that promotes experience-driven adaptations across brain regions and networks supporting the cognitive and behavioural capacities required in dynamic social environments. During this developmental phase, adolescents increasingly engage with larger peer groups. However, their ability to parse concurrent streams and track a target voice in the presence of interfering speech keeps maturing well into adolescence. Such skill relies on a network of functionally and structurally connected regions including prefrontal cognitive control, parietal cross-modal association, and the fine-tuning of temporal auditory voice perception. Adolescence begins with puberty onset, which is associated with changes in sex-steroid hormones, some of which are known to contribute to the maturation of brain regions involved in speech-in-noise processing (SiN). As part of the SensationaHL pubertal development cohort collection, we aim to investigate the neuroplastic mechanisms and myelination trajectories linked to pubertal stages and hormonal markers, focusing on brain regions serving complex cognitive and auditory skills. We hypothesize that myelination trajectories will correlate with pubertal stage progression, extending past puberty-offset. We also predict puberty-associated increases in gamma-aminobutyric acid (GABA) concentrations, a key modulator of neuroplasticity, in SiN regions of interest: the left pars triangularis and left Heschl’s gyrus. To address these aims, a cohort of 150 participants will be recruited and reassessed two years later, measuring pubertal stage transition surrounding puberty onset and offset. Pubertal hormone levels and stage assessments will be collected at the two timepoints, in addition to cognitive and auditory speech-perception tasks. Multimodal neuroimaging including single-voxel spectroscopy, diffusion imaging, and high-density electroencephalography is used at baseline and will be used again after two years to evaluate neurotransmitters concentrations, structural and functional connectivity and thus infer upon the mechanisms of neuroplasticity involved. Cross-sectional MRI preliminary results from approximately 70 participants (ages: 9-18 years; Early to Post-pubertal) collected to date will be presented in this poster. So far, preliminary findings suggest an increase in neurite density, decrease in orientation dispersion as well as maintained GABA concentration values within the targeted regions across age and pubertal status. These findings could allow to identify the neurobiological triggers of heightened auditory plasticity during adolescence and advance our understanding of how puberty shapes cognitive and auditory development in challenging environments.