The thalamus is increasingly recognized as a key node within epileptogenic networks, yet how recurrent seizure activity shapes its tissue integrity remains poorly understood. Existing evidence has largely relied on individual structural, functional, or electrophysiological modalities, limiting an integrated understanding of thalamic pathology. Here, we combined quantitative sodium, structural, and functional 7 Tesla MRI with stereotactic electroencephalography (SEEG) and clinical characterization to establish a multimodal framework for investigating thalamic involvement in drug-resistant focal epilepsy. Multiparametric MRI revealed widespread increases in total sodium concentration, providing the first evidence of altered thalamic sodium homeostasis in focal epilepsy, together with focal elevations of the short T2* sodium signal fraction within lateral thalamic regions and increased homogeneity of the functional MRI signal. Integrating these complementary measures identified a robust MRI profile that distinguished patients from controls and independently identified patients with SEEG-defined epileptogenic thalami. Reduced thalamic volume was associated with greater ictal thalamic recruitment, whereas multivariate behavioral analyses demonstrated that complementary MRI features differentially reflected the extent of the epileptogenic network, disease chronicity, and demographic characteristics. By integrating measurements spanning tissue pathology, intracranial electrophysiology, and clinical phenotype, this study establishes a framework for characterizing pathological network nodes in focal epilepsy. Such multimodal imaging profiles may support patient stratification and individualized therapeutic strategies, including epilepsy surgery and targeted neuromodulation.
R. Haast, J. Makhalova, L. Gauer et al.· medRxiv· 0 citations
Music is a uniquely memorable human creation that, when skillfully composed, can persist in individual memory (as in e.g., earworms) and cultural transmission (e.g. global hits or anthems). While both acoustic and statistical properties are known to influence a song’s memorability, the neural mechanisms that facilitate the engramming of certain musical sequences remain unclear. Current theories suggest that memory systems function as predictive internal models, enhancing learning when expectations are violated. Yet expected stimuli, by aligning with and reinforcing prior knowledge, also enhance memorability. How these two opposing processes arise from the brain’s sensitivity to statistical regularities, especially in naturalistic sequences, is not well understood. Here, we leveraged music’s intrinsic balance between expectancy and surprise, and examined the neural correlates of minutes-scale memorability using intracranial EEG recordings from nine patients with epilepsy performing a musical memory task. Quantifying the statistical surprise of each musical excerpt with PolyRNN, a polyphonic model of musical expectations, we uncovered a U-shaped relationship between musical surprise and memory performance: both highly expected and highly surprising melodies led to greater memorability. While neural pattern similarity between song repetitions was enhanced for low-surprise stimuli, high-surprise stimuli enhanced neural pattern separability in medial temporal regions, each mediating memorability in distinguishable ways. These findings reveal complementary neural mechanisms through which statistical structure shapes musical sequence memory, clarifying how the brain encodes complex, ecologically valid stimuli.
Mathieu Pham Van Cang, Paul Robert, Manuel R Mercier et al.· bioRxiv· 0 citations