Attention modulates the geometry of auditory representations
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Selective attention enables the brain to prioritize behaviorally relevant information in complex environments, yet the underlying neural mechanisms remain poorly understood. Here, we combined functional magnetic resonance imaging (fMRI) with representational geometry analyses to investigate how selective attention reshapes neural population codes in naturalistic soundscapes. Participants attended to individual sound objects presented either among distractors from the same category (3OW) or from different categories (3OA). We observed that attention selectively attracted neural population responses toward the object-alone template. This effect, evident in the low-dimensional PCA space, likely reflects a reorganization of the underlying high-dimensional representational geometry. This geometric effect was modulated by the surrounding soundscape: in 3OW, where all sounds belonged to the same category, attentional modulation was minimal, whereas in 3OA, attended representations were drawn significantly closer to their template relative to distractors. Category-specific patterns were also evident: for speech, attentional modulation extended beyond the auditory cortex to left-lateralized language regions, whereas for instruments and animals, effects were largely confined to bilateral auditory areas, including core, belt regions and the superior temporal sulcus. Finally, the attraction effect observed was behaviorally meaningful: higher subjective ratings of attentional engagement predicted smaller distances between attended and object-alone representations. Taken together, these findings demonstrate that selective attention reshapes neural population geometry in a context- and category-dependent manner, with geometric changes closely reflecting behavior.